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Fluid Management FAQ2022-03-08T15:29:11+00:00

Tramp Oil Skimming and Metal Working Fluid Management FAQs

This section of the site is designed to help in your understanding of metalworking fluids and how our coolant maintenance products will serve your objectives. Please let us know if we may be of any further assistance by calling 888-249-4855.

I am having an issue with concentrate siphoning from container2021-12-22T16:27:22+00:00
  1. Remove discharge hose from output holding container or sump.
  2. Verify concentrate container’s breather hole is open.
  3. Verify that the check valve is free of debris. 


I am having an issue with water draining into concentrate container2021-12-22T16:26:48+00:00
  1. Shut water ball valve off (check valve on end of standpipe is not rated to hold fluid under pressure).
  2. Check water ball valve for cracks or damage.
  3. If using a solenoid valve, install it on inlet before water supply (check valve on end of standpipe is not rated to hold fluid under pressure).
I am experiencing low concentrations or none at all2021-12-22T16:28:44+00:00

Low Concentrations or None at All

  1. Check the discharge hose. If you are NOT using the hose we provided, make sure you are using NO MORE than 40” of discharge hose, with a minimum UNINTERRUPTED ID of 1/2” for 3 gpm models, and 3/4” for 10 gpm models. Make sure that the hose has no kinks or other obstructions. If delivering mix through a garden hose, for instance, a proportioning pump is required.

    If you want a discharge tube that is longer than 40 inches), you will need to order a proportioning pump. The 7gpm MIXPP518 proportioning pump is our most popular model, it mixes water and coolant to concentrations between 1.4% and 12.3%.

  2. Examine the check valve at the bottom of the standpipe. Debris can keep it open, allowing concentrate to drain back into the drum. The check ball should be below the valve’s set screw.
  3. Check the water pressure. Our equipment requires a minimum pressure of 25 psi. TEST: Using the mixer with needle valve closed, fill a pail of known volume and time it. If you can fill a 1 gallon pail in 20 seconds there is enough pressure for our 3 gpm unit. If you can fill a 1 gallon pail in 6 seconds there is enough pressure for our 10 gpm unit.
  4. The needle-valve (dial) is numbered as a guide only. It does not indicate proportions. Turning the dial clockwise reduces coolant concentrate ratio.
  5. Check the coolant concentrate level in the drum. You may be running out.
  6. Check the viscosity of the coolant concentrate. Our equipment is designed for up to 500 SUS at 100° F. (SUS=saybolt universal seconds). 500 SUS is about the same as SAE30 motor oil.
How does a refractometer work?2021-12-20T21:10:50+00:00

Refractometers measure how much light bends as it goes through certain liquids. By placing your coolant mix on the prism and putting the prism cover in place, you create a mini-prism of liquid. If the liquid is pure water, then the refractometer will read zero on its scale (in fact, the light does bend somewhat, but the refractometer is designed so the water is the baseline).

The scale on the unit is based on the Brix Scale, which was designed to measure sugars in water. However, this scale is still used to compare coolant concentrations. Many coolant compounders have done a good job of compounding their fluids to that of the Brix Scale, so your readings are a one-to-one correspondence. Check with your coolant supplier to see if your coolant measures 1:1 with the Brix scale. If not, ask them for the refractometer factor, which you will need to multiply the scale reading by, for the actual concentration.

How does the Muscle Condensate Management System Work?2021-12-09T20:23:10+00:00

A. Oily air compressor condensate is injected
B. Air compressor condensate flows through diffusing chamber containing non-consumable media
C. De-watered air automatically exits via vent
D. Water and oils collect
E. De-oiled water forced down and through non consumable media to remove trace oils, then through tube to exit
F. De-oiled water automatic discharge
G. Contaminant oil floats to surface
H. Manual oil discharge



Will the Muscle Condensate Management System Work for Me?2021-12-09T20:17:47+00:00

In general, the Muscle Condensate Management System works most efficiently for those compressor operations that accumulate less than fifty gallons of condensate per week, allowing for the manual discharge of the separated oil once per week.

Zebra can calculate your totals, based off the below information, and advise how often you must release the compressor condensate and manually drain the separated oil:

1. Who is the compressor manufacturer?
2. What is the HP or cfm of your compressor?
3. What is the average room temperature in the location of the compressor?
4. What is the average relative humidity in that location?
5. What are the actual run hours of this compressor?
6. What is the appearance of the separated water portion (clear or more milky in nature?

Does your ZVac separate tramp oils from coolant?2021-06-03T18:21:34+00:00

No. It does, however, separate chips and other solids from water, water-soluble but non-explosive fluids, and straight oils. If tramp oil removal is your objective, utilize a mechanical skimmer or a coalescer.

Why is there so much maintenance required for equipment with particle filtration, such as the Zebra Muscle Deluxe w/Filter Coalescer?2021-06-03T18:20:27+00:00

Actually, there is very little. If you have particle filtration equipment, chances are you wanted to remove particles from your coolant! This is good because metals degrade coolant. And the smaller the particles are, the quicker they chemically interact with the coolant, causing coolant to break down on a chemical level and eventually be useless for lubrication.

You will need to change out the filter, whether it be a bag filter (as in this case) or cartridge filter (such as on the Zebra Snapdragon Coalescer), depending upon how many particles your operation creates during the machining or grinding process.

Just like an oil filter in your car, or a vacuum at home, the filtering apparatus will need changing once it has filled to capacity. If it is not filled completely, but requires too much pressure to pass liquid through it, then a bigger pore size will help. If you are trying to capture chips of 25 micron (.001″), you may want to step up to a 50 micron bag, and as chips fill it, the pore size will decrease gradually. Eventually, you will capture the smaller chips.

I see the Oxygenator in your catalog. Isn’t it the same thing as I can buy at the pet store, like the ones for fish tanks?How does the Zebra Odor Control Tablet control sump odors?2021-06-03T18:19:26+00:00

No. They are similar, but not an exact comparison. Since the Oxygenator will be used in an oil-based solution rather than water, we make sure to use the appropriate components for this application. But yes, they do work to discourage bacteria and other water-based growth, just like an aquarium type unit.

What is the extended filter option?2021-12-09T20:16:35+00:00

Customers familiar with our old F15DF design had a filter bag inside the center of the muscle. That option still exists, but we moved the bag from the inside to the outside. You can now mount a 10” filter housing off the top of the barrel, and insert whatever filter medium you think would work best. We offer a 100µ as a standard size, but what works best for you is something only you can know.

Please recognize that if your sump contains any kind of grease or heavy biofilm formation, this option is not for you. Also realize that going to a very small micron rating will probably mean frequent filter changeouts, because these small pore filters will clog very quickly on not just particles, but oil as well.

What should I do if my filter gets clogged frequently?2021-06-03T18:17:51+00:00

If your T strainer is getting clogged too frequently (and that frequency is totally up to you) then you should look into the following possibilies.

First, make sure that what is clogging your T strainer is particles. If it turns out that your strainer is getting clogged with grease or a biofilm, then there are other issues to deal with. Call us or read on for how to deal with grease or biofilm.

Second, think about what kind of particles are getting collected in the strainer, and how important it is for you to remove them from your coolant. If it turns out that there aren’t that many, and removing them from your coolant is a good thing but not critical, then we can look at putting an optional extended filter on the F16. If your chip load is heavy, and chip removal is critical to your operation, you should look into a dedicated chip removal system whose sole function would be to clean up chips.

How often will I have to clean out my T strainer?2021-06-03T18:17:11+00:00

No one knows. It all depends on your chip configuration, material, size, sump dynamics, and other factors. We can’t predict how quickly your strainer may become full of chips. In some cases, the strainer may not collect any chips at all.

When the strainer does become full of chips, you will notice a decrease in the performance of the F16. You may even notice that the eductor no longer works. In this case, clean the strainer by shutting off the unit. Then turn the strainer upside down to drain the coolant from it. When the coolant has drained out, then turn the strainer upright again and unscrew the bowl. Empty out the chips while holding onto the chip screen – you don’t want to lose that. Replace the chip screen, and re-screw the bowl in place – gently! It should not be screwed in too hard.

What is the T strainer for?2021-06-03T18:16:36+00:00

The filter in the standard T strainer is designed to catch chips that might clog the eductor. It also helps to keep those chips from settling in the bottom of your muscle. It’s much easier to open the T strainer and dump those chips into your chip bin, instead of shutting down the entire muscle, emptying it, and shoveling out chips that have settled in the bottom.

What factors should I address when choosing the appropriate Muscle™ Coalescer?2021-06-03T18:15:57+00:00

The individual selection of a Muscle Coalescer depends upon application factors such as:

  • Chip removal requirements (removal of suspended and floating chips or swarf) Metal chips chemically degrade coolant, so they are best removed, whenever possible. The smaller the chip size, the quicker this degradation takes place, so in grinding or cast iron machining, chip removal is definitely recommended. Choose the Deluxe w/Filter model whenever chip removal is of interest. Select the filter bag with a pore size relative to that of the chip size.
  • Type of coolant (full-synthetic, semi-synthetic or water-soluble oil) For full synthetics, the Plus model is recommended. For semi-synthetics and water soluble oils, the Deluxe model is best due to the additional coalescing media which helps separate the tramp oil from the base oil.
  • Intake attachment selection will be based upon sump factors such as access to the area where installed, fluid level fluctuations, and surface debris.

A dedicated Muscle is best for each sump that sits idle more than one shift. Idle sumps biologically degrade more quickly than those that circulate. The Muscle will remove the tramp oils and also continuously aerate and circulate the sump, preventing bacterial rancidity.

How do I know if I should get mechanical skimmers or coalescers to remove tramp oils?2021-06-03T18:14:17+00:00

It is a matter of what best “fits” your application as well as your equipment preference.

A mechanical skimmer will remove the tramp oil layer via a pickup mechanism, such as a disk, belt, or tube. The tramp oil is then discharged automatically to a waste container, which will need to be manually emptied as needed. Since tramp oils are best removed daily, as they are a food source for bacteria, it is recommended to have one on each machine sump to run as needed.

A coalescer draws in the entire surface layer of your sump, then gravity separates the oil within its holding tank for manual discharge to a waste container. Again, oil removal should be done daily, so dedicate a coalescer (such as a Muscle™) on each sump to run continuously, or daily utilize a portable unit (such as the Snapdragon™) on each sump.

More information on each product selection can be found in their product sections.

I bought a different brand coalescer many years ago. Can your coalescing media work with it?2021-06-03T18:13:36+00:00

Yes. Our media can be added to any coalescing equipment and will improve their effectiveness. It increases the surface area in the holding tank to improve the separation time. It is a non consumable, and will never need replaced.

Are there limitations to using the Muscle Coalescer on multiple machine sumps?2021-06-03T18:12:53+00:00

We supply the Muscle with a small submersible, centrifugal pump so it can fit into most machine sumps. It is pretty rugged for most applications, however, it is not designed to handle a lot of air intake. If reintroducing this pump to every machine every day, it may cavitate and burn out prematurely unless you keep it primed with fluid. It may also be time-consuming to reinstall the pump and intake attachment at each use point. So, labor costs are also a factor.

Although the unit is available with a drum dolly, this dolly is only meant for ease of maneuverability when moving around your machine, such as during machine cleaning and recharge. A portable unit should be on a rugged frame for system protection, like on our Snapdragon™ Series. If your budget is limited, we also offer an air or electric diaphragm pump upgrade option for the Muscle unit.

How do I know that the Muscle Coalescer will effectively separate tramp oil from my coolant?2021-06-03T18:12:13+00:00

The Muscle has a hold time of 15 minutes, and with its coalescing media, will be able to separate tramp oil which naturally gravity separates in 20 minutes or less. To determine the amount of tramp oil that will naturally gravity separate in 20 minutes, you will need to take a miniature separation test for each sump.

Using a clean, clear plastic pop bottle, for instance, dunk it in from the top of the sump to the bottom, for a cross section of the solution. Cap the bottle off and shake it vigorously for 10-15 seconds. Then let it stand to naturally reject the tramp oil while timing the process. Whatever tramp oil separated in 20 minutes will be the amount that the Muscle will be able to remove from that sump.

To note, as coolant ages, and the more base oil there is in your coolant, tramp oils will take a longer time to gravity separate. You may find that older sumps take longer for the oils to separate. However, if you were to use the coalescer from the first day of a recharge, it will remove the tramp oil effectively.

Also, add on high-pressure coolant delivery systems cause tramp oils to deeply emulsify into the base coolant because of the pressurization of the solution. During the separation test, you may see mostly a separated inverse layer, somewhat like a milkshake. This may be the only separation, yet this layer is still best removed. If using a coalescer, it is recommended to run the coalescer only when the machine pumps are not operating, whenever possible, for the best effectiveness.

What is the benefit of using a coalescer to remove the tramp oil over that of a mechanical skimmer?2021-06-03T18:11:30+00:00

A mechanical skimmer only removes the tramp oil and needs regular maintenance to keep the chips and other debris that are collected off of the pickup mechanism and the oil scrapers.

The Muscle™ Coalescer will remove the oil layer AND keep the coolant sump in constant circulation, helping to prevent bacterial contamination which degrades coolant. If the machine tool runs less than 2 full shifts per day, a Muscle Coalescer will help to keep that sump in its best overall condition, preventing bacterial problems and coolant degradation. Little to no maintenance is required, as cleaning of the coalescer only needs to be done if their is a buildup of chips and debris within it, or if it is biologically contaminated. Zebra manufactures models which have chip collection capabilities to remove chips which also help to degrade coolant.

If using a coalescer is impractical or impossible near that machine, use a mechanical skimmer to remove the tramp oil and run an aeration device, such as the Zebra Oxygenator™, whenever the pump does not run to help keep bacteria at bay.

What factors should I address when choosing the appropriate mechanical skimmer?2021-06-03T18:10:20+00:00

Selection of a mechanical skimmer is based upon sump or tank factors such as:

Access to the area where oils naturally collect (mount location of the skimmer)
Reach needed to the lowest fluid level (distance from mounting point)
Required rate of oil pickup (quarts or gallons per hour)
Temperature of the solution (as in wash water)

If using a mechanical skimmer, we recommend the use of the Diverter accessory, which mounts below the skimmer to redirect any removed coolant back to the sump or tank. See the Diverter section for details.

If the sump runs only one or two shifts, then we also recommend the use of an Oxygenator™ during the time the pump is down. It will help to prevent bacterial rancidity by keeping oxygen in the fluid. See the Oxygenator section for details.

How do I know if I should get mechanical skimmers or coalescers to remove tramp oils?2021-06-03T18:09:10+00:00

It is a matter of what best “fits” your application as well as your equipment preference.

A mechanical skimmer will remove the tramp oil layer via a pickup mechanism, such as a disk, belt, or tube. The tramp oil is then discharged automatically to a waste container, which will need to be manually emptied as needed. Since tramp oils are best removed daily, as they are a food source for bacteria, it is recommended to have one on each machine sump to run as needed.

A coalescer draws in the entire surface layer of your sump, then gravity separates the oil within its holding tank for manual discharge to a waste container. Again, oil removal should be done daily, so dedicate a coalescer (such as a Muscle™) on each sump to run continuously, or daily utilize a portable unit (such as the Snapdragon™) on each sump.

More information on each product selection can be found in their product sections.

I have an Simple DIsk Skimmer and the motor keeps burning out. Help!2021-06-03T18:07:24+00:00

The Simple Disk Skimmer comes equipped, standard, with an intermittent duty motor. That means that it needs time to cool down since it does not have a fan. Run time is 40 minutes maximum with a 20 minute cool down period. If this is a problem for your application, then you can upgrade the motor to a fan cooled type. Give us or your distributor a call for details.

I have a belt skimmer, but it’s not a Zebra. I think the company went out of business, and I need a replacement belt. Do you have them?2021-06-03T18:06:40+00:00

We supply replacement belts for other brand skimmers, but have only the 3/8” cogged, flat poly, or flat steel variety. All we need from you is the width and OAL (over all length or end-to-end) measurement. If you do not have the original belt to measure from, then we have a specifications worksheet which you will need to provide a few measurements of your brand skimmer. We can calculate the OAL from there and get you a replacement to get you back up and running.

I have only 3 CNC machines in my small shop and money is tight. I need a mechanical skimmer to remove tramp oil from the sumps, but I also would like to skim off a holding barrel. What is the best product for this application?2021-06-03T18:05:51+00:00

Either a Zebra Belt Skimmer or Sidewinder™ Tube Skimmer, depending upon the access to your sumps. We recommend also mounting the Diverter and the Lockjaw™ Mounting Clamp. With the Lockjaw, you can then easily move the skimmer set up between each sump as well as to your barrel.

How long will my ZVA tube last?2021-12-22T19:35:28+00:00

Short Answer: Many years.

Long Answer: It is extremely rare for a ZVA tube to break for any reason. This is why we give a standard 2 year warranty on all our tube welds. We even sell an extended 5 year warranty for those who are interested.

Why don’t they break? For one thing, we put every tube we make through a rigorous QC process for one, rejecting every tube that fails any single test. And then we put a sample of every batch of tubes through a destructive test.

Mechanically, our tubing is very strong, and our weld is many times stronger than the tubing.

If tubes don’t break, then how could it happen?

The most obvious reason is that it may have been cut. Sometimes this happens if someone closes a sump without seeing the tube. It’s almost always an accident. You can tell when the tube is cut because the edges of the cut are very straight.

There is another reason why the tube can break – chemistry.

Without getting too complicated, water breaks the mechanical weld. That’s right, our weld is mechanical, and water breaks it apart.

Like velcro, the polymer chains that make up our tubing join together during the welding process. The ends are like bent fingers that hold onto each other. Mechanically, this is incredibly strong.

However, our tubing is made to resist oils, the kind of oils that are found in metalworking fluids. If our tubing is exposed to water, the water attacks the polymers, relaxing the fingers. When the fingers straighten, the ends of the weld let go. And the weld breaks.

Where does the water come from?

A machining center is designed to hold metalworking fluid (MWF) that makes cutting metal much easier than not using anything at all. If you use straight oil, the cutting is easy but there is too much heat. If you use straight water, then there is very little heat but the cutting is hard. Also, with water, the expensive machine will rust and be ruined. By using a specific mixture of oil and water, the cutting can be easy and cool at the same time.

The problem is that the MWF is made to be used at an exact ratio of water to oil. Most of the time this ratio is 10 parts water to 1 part MWF concentrate. If someone doesn’t mix the MWF correctly, then the ratio changes.

If the ratio becomes 12 parts water to 1 part MWF concentrate, then that means there is too much water in the mixture.

This is where the water comes from. This “free” water is available to attack the weld of our tube. And the mechanical weld breaks.

However, this free water is also available to damage the more expensive machine. This free water also makes cutting more difficult, so that tools don’t last as long.

In this way the ZVA tube weld works like an electrical fuse. It breaks at the weld indicating the presence of too much water. Replacing a failed tube is very inexpensive and easy. Repairing an extremely expensive CNC machining center is difficult.

This is why, when Zebra learns of a tube break, we take extra care to learn about how the customer is taking care of their machine and their MWF. We teach them that the skimmer is giving them a warning. Once our customers understand that, they appreciate the information and learn to take better care of their machines.

How Zebra changed the market.

When the ZVA was first introduced 20 years ago, there were many tube breaks. We took care of all our customers and learned why the breaks happened. If the break is our fault, we always replace the tube for free. If the tube break is because of chemistry, we replace the tube one time for free, but we teach the customer why this happens.

Today, there are almost no reports of tube breaks due to chemistry. We are proud to have taught our customers the proper way to maintain their sumps. Not only does this mean they have fewer problems with the skimmer, but their machines and their production work much better.

What are the benefits of using the Diverter™?2021-06-03T18:02:38+00:00

If your mechanical skimmer is not on a timer, it will lift off your coolant too.

Most coolants have some type of oil to their base (ie. mineral oil, vegetable oil, etc.) for lubrication purposes. A mechanical skimmer loves oil, and does not know the difference between the bad tramp oils you need to remove from your sump and the good oils that may be within your coolant base. It will pick up anything it knows as oil…period.

The Diverter does know the difference, and uses gravity separation to separate out the tramp oils form the coolant, and will revert the coolant back to the tank. All you will have in your waste container is tramp oils, saving hundreds of dollars a year in wasted coolant.

However, the Diverter does know the difference, and uses gravity separation to separate out the tramp oils from the coolant, and will revert the coolant back to the tank. All you will have in your waste container is tramp oil, saving hundreds of dollars a year in otherwise wasted coolant.

The other option is to put the skimmer on a timed cycle, so it runs only as long as the oil layer is present. Once the tramp oils are picked up, the skimmer is turned off by the timer. Most often, getting this timed cycle just right is the challenge, and can take several days and a lot of hassle!

My mechanical skimmer no longer picks up oil, why not?2021-06-03T18:01:49+00:00

Mechanical skimmers (disk, belt, or tube type) are designed to pick up oil, and will continue to do so as long as the oil layer IS just oil. Once the pickup mechanism no longer attracts and picks up the surface layer, the layer has become something other than just oil (referred to as biofilm) or it is coated with a rejection chemical.

Biofilms are formed when an abundance of bacteria have colonized. They combine with their food source- the oil layer. Until the bacteria are under control, this mucous layer will grow larger, clog lines and filters, give off foul odors, and eat away at the good stuff in your coolant. Nothing will pick it up except for a coalescer or shop vacuum. It is recommended that the machine be fully cleaned and decontaminated, then recharged with fresh coolant. You will know the machine is decontaminated when its rinse bath is a pH of 7 (that of water).

A rejection chemical is a chemical that is in your coolant blend or from another source (such as rust preventative or anything else that may end up in the coolant soup). The most common chemical that can cause this rejection is silicone. Once it is wiped off the pick up mechanism, the skimmer will work-but only until it is recoated! We recommend the use of the Muscle Coalescer instead of the mechanical skimmer for this situation.

What else is Uncle Earl’s good for?2021-06-03T18:00:42+00:00

It works great to remove grass and mud stains from clothing. Stay tuned on this one, we are finding more applications as each day goes by!

Is Uncle Earl a real person?2021-06-03T18:00:03+00:00

He is, but he’s not our uncle, just a true friend. Earl was born during the Great Depression in Medina County, Ohio and still lives there. Nobody wasted anything in those days, and his thrifty upbringing has stuck with him his whole life. “We couldn’t afford toys when I was a boy, so I used to make my own,” he says with a laugh. When he reached his teens, he fell in love with cars and developed a knack for working with his hands. Later he joined the Army, and became an engineer and machinist and served in the Korean War. He is one of those hardworking, no-nonsense people that gets things done. Earl is a man of total integrity and has a quiet, inner strength. He represents those qualities that make America great. Fact is, America was built on guys like Earl!

My shop uses liquid soap. Does this soap only come in bar form?2021-12-22T19:29:46+00:00

No, the soap is also available in liquid forms. We stock it in 8 oz and 1/2 gal versions. Visit to order.

Is Uncle Earl’s really made with all natural ingredients?2021-06-03T17:58:32+00:00

You betcha! Zebra is proud to acknowledge the simplicity and goodness of organic chemistry. Unlike other soaps on the market we make ours totally from scratch.

Has the use of Uncle Earl’s actually helped anyone solve their eczema (dermatitis) issues?2021-06-03T17:57:46+00:00

Yes, we have heard from many metalworkers that their skin problems have improved or totally cleared up.

How does it protect the hands like barrier creams do?2021-06-03T17:56:49+00:00

Uncle Earl’s contains moisturizing agents which lightly coat the skin. These moisturizers then help to prevent irritation when your hands are exposed to skin-irritating chemicals, such as in MWFs.

How can this soap clean so well considering there is no grit in it?2021-06-03T17:56:03+00:00

Uncle Earl’s is formulated with other cleaning agents which chemically (not mechanically) break up and wash away grease and grime.

Why is there no grit in Uncle Earl’s Soap for Machinists?2021-06-03T17:55:17+00:00

Made for the 21st century machinists – washing their hands all the time, there is no place for grit. Soap that contains abrasives generally breaks the smoothness of the skin. When your hands are then exposed to certain fluids, such as metalworking fluid (MWF), your skin generally becomes more irritated and encourages certain skin problems, such as dermatitis. Sandpaper-like soaps were formulated over 100 years ago and like tooling today the technology has improved over time.

Why does coolant foam?2021-06-03T18:28:58+00:00

The most common reason for foaming coolants is a lack of minerals in the water supply (also known as soft water). We suggest checking the hardness of your water using our Hardness Testing Sticks. This quick and easy monitoring step will prevent overflowing sumps and help to ensure that, without foam, any tramp oils will separate more quickly on the surface for removal.

The second reason for foaming coolant is over-aeration. This can be caused by high pressure delivery systems and/or piping routes (never use a 90° angle) as well as aerating devices, such as our Oxygenator™ (whenever your machine pump is running, you can unplug it without negative sump effects).

My coolant separates out of the water after mixing it. Why is this happening?2021-06-03T17:53:17+00:00

This is due to an excessive amount of minerals in your water supply (also known as hard water). The abundance of these minerals (mainly calcium and magnesium) prevent, on a chemical level, the concentrate from remaining in the mixture. It is possible, even with softer water, for there to be an abundance of these minerals over time, due to the effects of evaporation at the sump level.

If this is a consistent issue, use the Zebra Hardness Testing Sticks to check the level of your water hardness and compare it to the product data sheet for your coolant. Most coolant manufacturers will specify what hardness range their blend can withstand. If your coolant is outside the range, you can use an additive to decrease the hardness, or even consider RO (reverse osmosis) water.

Hard water can also contribute to surface grease formation, which is not readily removed via mechanical skimmers since its surface tension is different than that of straight oil. Coalescers would work better for their removal. Grease formations also contribute to premature filter blockage.

Other negative factors due to hard water are rust and gummy residues, either on parts or machine interiors.

How does the Zebra Odor Control Tablet control sump odors?2021-06-03T17:52:07+00:00

Our Odor Control Tablets help to balance the pH of your sump. They are not a perfume. They prevent the foul smells that are given off by bacteria as they decay. Used as directed, they work with all coolants we currently know of, and are perfectly safe to you and the environment.

If foul smells are a routine concern, make sure your concentrations are correct and consistent, tramp oils are removed, and there is proper aeration to each sump, especially when they are not in use.

Why is it important to check the pH of my coolant (and what is pH anyway)?2021-06-03T17:50:55+00:00

In basic terms, pH is an indication of the acidity or alkalinity of a fluid. Water has a pH of 7, which is neutral. An acidic fluid will range from 0-7 pH, and an alkaline fluid will have a range of 7-14 pH.

pH levels in your coolant drop due to bacterial emissions. Since coolants have an operating range of 8-10 pH, even a .2 drop in pH level can cause a host of problems, ranging from rusty machines and parts to sump odor and skin irritations. With consistent pH monitoring and bacterial control methods, these problems can be prevented.

Why does the concentration of a sump increase even though the same concentration is used for each refill?2021-06-02T14:30:17+00:00

At the end of the shift, the missing volume of a sump is not only due to carry-off. It is also due to the evaporation of the water within the mixture during the machining process. Since water composes up to 95% of the volume, even a slight evaporation rate can change the overall concentration significantly. You will need to do a calculation by volume to determine the appropriate concentration for the refill.

Please refer to the example below. To note, evaporation rates may be different between machines and/or processes. It is best to calculate this rate per machine sump and per process to ensure consistent concentrations.


Known Factors:
Desired Sump Concentration: 5%
Total Sump Capacity: 50 gallons
Volume of Make-up Solution Needed: 25 gallons
Current Sump Concentration: 8%
Unknown Factors:
Required Make-up Concentration
Determine the volume of concentrate needed for the entire sump (volume of 50 gallons at the desired concentration of 5%):
(.05 x 50 = 2.5 gallons of concentrate)
Determine the volume of concentrate needed for a make-up solution if only 25 gallons are remaining in sump at 8% concentration:
(25 x .08 = 2.0 gallons of concentrate)
(2.5 gallons of concentrate originally in entire sump)
-2.0 gallons in remaining sump
.5 gallons of concentrate needed for make-up
Determine concentration for make-up solution:
(.5 gal of conc. ÷ 25 gal fluid required = .02, or 2% conc.)
The sump now needs to be filled with a 25 gallon make-up batch at a concentration of 2%.

When I put a drop of coolant on my refractometer, it is so blurry I can barely make out a reading. Does this mean that I need to replace it?2021-06-02T14:29:13+00:00

It means you need to replace the coolant in the sump, and not the refractometer. When a definitive reading is not possible, the sampled coolant has deeply emulsified tramp oils in it. It is still usable for the lubrication process, but may promote excessive coolant mist, feed bacteria which degrade coolant, and contribute to health and safety issues. Not to mention you’ll never be certain of its concentration. Your call.

One of the refractometers I have reads 1% lower than all the other ones in my shop, even though the concentrations are all the same. Why is this?2021-06-02T14:28:24+00:00

This refractometer probably needs to be recalibrated. Use water (tap water is okay, but distilled is best) to zero the scale (in accordance with the instructions for your unit), then try it again.

I have a refractometer with a scale of 0-10. My coolant is supposed to run at 8%, but when I check it with the refractometer, I see nothing registering on the scale. What’s the deal?2021-06-02T14:27:30+00:00

Your concentration is way too high and off the chart!

I am trying to determine the best refractometer for my application. There are various scales to choose from. How do I know which one is suitable?2021-06-02T14:26:50+00:00

Refractometers use a scale called the Brix Scale. This scale was initially designed for measurement of sugar content in a water solution, but it is still used for metalworking fluids. Some coolant manufacturers make their blend so it measures 1:1 with the Brix Scale. Some do not. Check the product data sheet for your coolant’s “refractometer factor”. You will need to multiply this factor by the reading you see on the scale to determine the actual percent concentration of the solution. But, to determine which scale is the best, you will need to divide the required concentration(s) by the refractometer factor.

So, say your refractometer factor is 1 and you need a 10% concentration. You will only need a scale that goes up to 10 (10 / 1 = 10).

But, say your refractometer factor is 2 and you need a 8% concentration. You will only need a scale that goes up to 4 (8 / 2 = 4).

Yikes…you need a 20% concentration and your refractometer factor is 3.7! You will need a scale that goes up to 5.4 (20 / 3.7 = 5.4).

It is recommended, however, to use a scale that has a higher range than what you are trying to achieve, since evaporation at the sump level will increase the concentration. You will then be able to read whatever concentration the sump is at.

Why is it recommended to install a water filter for the Zebra Proportioning Pump?2021-06-02T14:24:49+00:00

The proportioning pump has many small parts which can wear if given the opportunity. Using a pre pump water filter will decrease the likelihood of wear since it will capture any tiny particles that may flow through your water line.

I have the Zebra Machinist Mixer (P/N MIX03725) and I have the dial set at 7 but I am getting a 15% concentration. Is the mixer defective?2021-05-28T20:11:07+00:00

No, the mixer is not defective. The numbers on the dial are for reference only, and not an actual calibrated scale. The Machinist Mixer uses a venturi to create a vacuum which draws the concentrate through the standpipe to then mix with the water. It does this using the water pressure on the incoming side. The concentration on the output side will depend upon your concentrate’s viscosity as well as your incoming water pressure.

You will need to verify the outcoming mixture with a refractometer, then make any necessary dial adjustments. To note, we recommend installing a pressure regulator on your water inlet if you have changing water pressures. This will ensure the correct output concentration, once set by the dial. It is also recommended to use the Mixer Lockout if operators are unaware of this, or if outright tampering is an issue.

Why can’t a venturi mixer, such as the Zebra Economy Mixer or Machinist Mixer, deliver the coolant mix through a garden hose to all the machine sumps?2021-05-28T20:08:44+00:00

A venturi mixer pulls the coolant concentrate via pressure created by the water source, then mixes it with the water in the inner chamber. When attaching a garden hose to the outlet of a venturi mixer, the water pressure is instead used to push the column of fluid through the hose, resulting in a loss of coolant concentration, or none at all.

The Zebra Proportioning Pump is required for long distance coolant mix delivery such as through a garden hose or even through hard conduit. It works by a process called positive displacement whereby a piston is moved by the water pressure. Each time the piston moves, it draws a given amount of coolant concentrate which is then mixed with the water through the hose or conduit. Therefore, it does not lose its ability to pull concentrate even though it is also pushing the column of fluid. The Zebra Proportioning Pump will be able to mix and deliver the coolant mix up to 800 feet laterally, and up to 20 feet vertically! We recommend utilizing a check valve on the outlet side for any vertical installation so the column of fluid does not create back pressure to the pump.


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