Pump backflow in Coleman filler tank

[trinityspeedwash]

I thought I understood how the water flows in my wash worked, however, after today I am bit bamboozled and I hope to get some help.

Issue:
- When set to "Rinse", high-pressure wash, the 5CP pump runs and produces good flow/spray in the bay. All good.
- A couple of days ago, water was overflowing. Upon checking ...
- When pump set to "Rinse", water seems to flow up into the water filler (picture 2) - basically the wrong direction - to the point where the water from the filler will come out of the overflow holes.
- When I close the valve below (picture 3), the bay keeps working just fine and water does not flow back into the filler.
- The only happens for one bay ... all other bays do not have this issue

So I am a bit baffled. I thought the pump receives water through the inlet (picture 1), which comes from the gravity fed water filler (picture 2). More specifically, the thicker blue hose past the values (picture 3) does run to the pump's inlet.

Clearly, I am not understanding something, but how would the water flow (backwards) into the filler when the pump is running, as opposed to draining out?

Has anyone experienced this?

 

[Blanco]

Your check valve that you have circled is bad. You can pick up a 3/4" low pressure check valve from Lowes. When you install it make sure you put it in the correct direction with the arrow pointing down. Your pump is still getting water from your rinse solenoids (red lines) at the bottom of the pump stand even though you closed that ball valve. When that ball valve is open your rinse solenoid water is pushing back into the tank because that check valve is failing.

Also this has nothing to do with your issue but those ball valves at the bottom of your tank should never be fully open. You want to close them off slowly while on HP until you hear the pump cavitate and starve for water then slight open until it sounds good. This will help with drawing product into the pump, making your soap look a lot better, and reduce your current chemical dilution ratio.

 

[slash007]

That check valve could also just have something in it keeping it open, check it before you replace.

 

[Blanco]

Spend $25 and just replace it unless you will have to take off all the hoses, the tubing, the tee holding the push fittings, and the elbow on the right just to spin it out of there. Twice. Nothing I hate more than doing something two times. Let alone to try to save $25. Also that’s an original. Few of them have already been replaced. I’m sure it’s served its purpose for last 20 years.

They should have made that with a male and female jic above check valve for easy service. That’s what I did to my pump stands

 

[Blanco]

Forgot to add the Lowes link. Its actually $15.

https://www.lowes.com/pd/ProLine-Reliabilt-Brass-3-4-in-Fip-In-line-Check-Valve/5013024151

 

[trinityspeedwash]

As usual, you guys are right.

I took apart the 4th check-value to find that it was completely broken down. New one in place and I am back up and running.

As always, appreciate the insight.