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Filter On Suction Side Of Pump?


Gun Plumber
May 20, 2020
Member Number
Greenwood, CA
What would happen if I put one of these filter housings with a 5 to 10 micron cartridge inside on the suction side of a 10gpm positive displacement pump? There’d be less than 18” of 3/4” ID hose between the tank and filter, and less than 18” between the filter and pump.

Will it implode? Cause cavitation? Cause covid? Work fine?
What are you pumping ?

Viscosity of what you are pumping ?

Would mOst likely be better to use that kind of filter to pressure thru and a sock filter to use before pump assuming you are pumping water.
First issue I could see would be if it has an air purge button.
Is the filter rated for vacuum?
If not, it could suck a lot of air (it's far easier to "leak" air than heavy oil).

If pumping a viscous fluid, or filter loads up, cavitation is a definite possibility.
Put pressure / vacuum gauge between filter & pump, maybe with a telltale?

Need details of what you're looking to draw through what type of filter.

EDIT: zoomed in on photo - water purification - you're looking to draw water through it?
I'd be very concerned about cavitation when the filter loads up - vacuum gauge is your friend.
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In general, even if the filter can be sued on the suction side of the pump. It is not the best practice and should be avoided if possible.
This would be for water based machine coolant. The viscosity is not much thicker than water.

My first thought was to use a low pressure pump to push the coolant through the filter into a "clean" tank. Then the HP pump can pull from the "clean" tank, run through the tools, then drain back into the dirty tank. But I'd love to simplify this, if possible. The pressure side may be 300-500 PSI, which is pretty costly to filter.
what is the return pressure? install a filter on the return side and dump into your clean tank, feeding the pump clean coolant
low pressure impeller pump at the dirty tank, through the first pass filter and to the HP pump. The impeller pumps don't care about a little grit, you will want a rock catcher in the tank to keep it from sucking swarf though.
Nope. Don't do it. It will be nothing but a headache. Get another pump, use it to filter the supply for the machine pump.
OK, my machine OEM pump is a centrifugal pumps, that is rated at 22 gpm @ 13 psi, if I am reading the spec sheet correctly (https://product-selection.grundfos.c...cid=1001498623). I know when measured at the tool, it is putting out 6gpm @ 35 psi. I am pretty sure a centrifugal pump can be dead headed without damage. Now I am thinking about skipping the second tank, have this pump plumbed though the filter then to the positive displacement high pressure pump.

The high pressure pump doesn't have any specs regarding max input pressure, but I highly doubt my OEM pump would make near enough to cause issues.

Any issues with this? The OEM pump is not cheap, so making sure it wouldn't be harmed is important.
I would put a course filter on the intake, I use pantyhose on my gold highbanker pump :flipoff2: . Then put a fine filter on the high pressure side.
I have that same filter before a pressure washer on my Telebelt truck. Works just fine if you can get a foot of head on it.
I am using a gear pump to pull thru a filter before going to a saw.
Not the same thing, but log splitters have the filter on the suction side.....
Putting a filter before a pump is done all of the time to protect the pump, but what you need to be able to do is assure that the pump is seeing the required positive suction head to avoid cavitation on the suction side. I just installed a series of positive displacement chemical injection pumps with heavy viscous liquids using nothing more then gravity head through filters on the inlet side, but this required feet of inlet pressure head along with humorously oversized inlet piping.

Since you don't have the HP pump specs posted there is no way to check what the actual requirements are in your application. However given the configuration that I assume you have trying to work of the sump on a lathe you will not have any real gravity head to work with and would be likely forced into plumbing it in down stream of your existing LP pump even without the filter. Now you likely could get away with deadheading the centrifugal pump but it is really not good practice. Puting extra strain on the motor and seals that will result in reduced service life, how much I can't say for sure as the demands on that pump really aren't that high in either service or what I would assume to be duration either. Best way to set it up would be: Tank --> LP pump --> full flow PRV set between the service and deadhead pressures --> Filter body with differential pressure gauge to monitor plug-age --> HP pump --> HP PRV just in case for the gold plated option to protect the positive displacement pump, if not already integral to the pump itself.
Ok, got it kind of temporarily rigged. My OEM centrifugal pump > 25 micron filter > HP positive displacement pump > tools.

The OEM pump would typically be about 38 psi before the filter and about 35 after with a tool in position. It was around 20 psi free flow/no tool.

Now with the HP pump on, it’s about 20 psi before and after the filter. I’m far from an expert, but to me, that sounds like it’s keeping up about right.

Now to fix all the other issues that popped up with 300 psi coolant, leaking fittings at tools, coolant foaming, and mist control...
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