Help Needed: Persistent Pump Cavitation Issue in 3-Bay Self-Serve Car Wash

[406CarWash]

Hi everyone,

I’m running a direct-service 3-bay self-serve car wash and have been dealing with a frustrating issue involving pump cavitation. The pumps start to cavitate every 10-15 seconds, causing a drop in pressure, but then the pressure returns briefly—only for the issue to repeat continuously. This happens across all three settings: rinse, wax, and soap.

Here’s what we’ve done so far:

• Installed a new Dema injector: We were struggling with consistent soap and wax injection, but the new injector seems to have resolved that issue.
• Replaced all Watts pressure regulators on the three lines to ensure the lines are properly regulated.
• Checked the well pump: It appears to be functioning properly, supplying what seems to be enough water.

Despite these efforts, the cavitation problem persists, and I can’t figure out what’s causing it. I’d appreciate any insights or suggestions on what else to check—especially if you’ve experienced something similar. Could there be an issue with backflow, air leaks, or blockages I’m overlooking? Could air be pulled from our weep system that is somehow making it to the pumps?

Thanks in advance for any advice!

 

[mgmtoo]

look for a cracked or leaking intake fitting.

 

[Randy]

Are the fed by well water pressure, no gravity tank? Are the wash, rinse, wax cold water? I think your starving the pump for water. Take one of the regulators out and hook the water up straight into the pump and try running it, you won't get any chemical out of the gun but you to eliminate everything else. It could also be your pulling air in somewhere. Did this problem start when installed the DEMA injector? Pictures are always nice

 

[I.B. Washincars]

Are they gravity fed from a holding tank? I had a Mark VII Proline system that did that. Every time the float valve would open, it would churn and aerate the water in the holding tank. This is when the pumps would chatter. The float valve was shooting the water directly into the hole in the bottom of the tank, which made for a lot of churning. I replumbed the valve so it wasn't directly over the hole, also extended the outlet down below the water level, and put an elbow on the end so it wouldn't slam the water directly into the bottom of the tank. This made for much less agitation inside the tank. If you don't have a gravity fed system like this...well, it's probably something else.

 

[406CarWash]

Are the fed by well water pressure, no gravity tank? Are the wash, rinse, wax cold water? I think your starving the pump for water. Take one of the regulators out and hook the water up straight into the pump and try running it, you won't get any chemical out of the gun but you to eliminate everything else. It could also be your pulling air in somewhere. Did this problem start when installed the DEMA injector? Pictures are always nice

Thanks for the response and questions. Correct, no gravity tank. The soap is hot water. Wax and rinse are cold. We did take one of the Watts regulators out on one line and no change. I'll try running that line on rinse as a test to see what that does. Problem started before the Dema injector installation. I'll grab some pics of the system.

 

[Randy]

I don't have gravity tanks. My pumps are fed with reduced pressure city water. The attachment is of my pumping system.

 

[406CarWash]

Here are some images of our system. Still can't ascertain the problem.

 

[Randy]

Here are some images of our system. Still can't ascertain the problem.

It's not plumbed up right. Look at the picture of how my pumping system is plumbed up and copy it. You don't need the 2 check valves on the inlet. You want to use a Generant regulator if you can't get the Watts regulators to work properly.

 

[Dick Nitro]

I second what Randy said

and if it were me, I’d immediately replace that big 3/4” check valve and it’s reducer bushings with a simple swivel and a nipple. While it’s apart, make sure the other check is in good condition.

is that a plug or some type of PRV on that 90? Try to minimize connections as any of them can be a source of air Ingress

 

[OurTown]

That looks like a belt-drive pump, not a direct-drive pump, although that has nothing to do with the issue.

 

[Dick Nitro]

Let us know if these changes don’t solve the problem. There’s another possible concern regarding that model of cat pump, but it’s not worth talking about unless everything else has been addressed