Pressure falls drastically on soap/wax

[CWdummy]

I just got a previous similar problem solved , but need help. I have had this well maintained 6 bay carwash for over 30 yrs. Never had a problem I could not fix—until now.
To recap this problem—Rinse comes off city water through a solenoid and works perfectly. When I select wax or soap (which comes out of same high pressure wand)the pressure drops tremendously, from 1200# to 400# and the boom and hose shakes. I have replaced every hose that has anything to do with that pump, ie 1/4” soap and wax hoses to tee that goes into 3/4” check valve and then into pump. Replaced check valve also. Even replaced 3/4” supply hose from tank water to pump. In other words, I thought air was being sucked in from some where. After all this failed to fix, I removed anything that was related to soap or wax and just directly plumbed the water to the pump. Water flow is great. Figured if that fixed it, that proved air was being sucked in somewhere. Well, that did not change anything. So, in my simple mind now, I say the problem is not external, but internal to the pump. So today I rebuild the Cat 530 pump with new high and low seals, against my better judgment. Because I figured if pump was working excellent on rinse, that eliminated any internal issues with pump. Well, I was correct. Problem has not changed even after pump rebuild. I just came home pissed off and to step away from it for a few hrs. I have not checked the valves yet. Does not sound like a valve problem, but that is next. In 30 plus years I have replaced/repaired maybe 5 valves. I feel I have eliminated any air sucking and eliminated any starvation issues. I am about ready to offer a free steak dinner to someone who can solve this mystery.

 

[Randy]

Try this disconnect both the Soap and Wax from the pump, plug off the Soap and wax ports at the pump and then run the pump. If it runs smooth then you know it's either the soap or wax line that's drawing in air, if it runs smooth reconnect the soap and run the pump if it runs smooth reconnect the wax. Report back, pictures are always nice.

 

[Roz]

Sounds like water starvation. Have seen it once when a valve did not open properly. Check the area where you make switches as it sounds like a similar issue.

 

[Keno]

Is the check valve operating correctly?

 

[GoBuckeyes]

We use Dole Dual Inlet Valves on our pressure fed systems. Each side has a diaphragm exactly like the ones used in hydrominders. When they go bad it does exactly what you described...full pressure, then kind of a shudder and pressure drops to basically nothing. Ninety percent of the time the diaphragm looks fine but something is wrong with it. Don't know what kind of valve set up you have but I think Roz is on to something. Pictures help like others have suggested.

24 Volt AC Double Inlet Valve | Dole Valves | 2550.34 (kleen-ritecorp.com)

 

[CWdummy]

Try this disconnect both the Soap and Wax from the pump, plug off the Soap and wax ports at the pump and then run the pump. If it runs smooth then you know it's either the soap or wax line that's drawing in air, if it runs smooth reconnect the soap and run the pump if it runs smooth reconnect the wax. Report back, pictures are always nice.

Is the check valve operating correctly?

Yes

 

[Randy]

Yes

What does "Yes" mean? Does it mean that your going to try that suggestion or does it mean that you've already tried that suggestion?

 

[PaulLovesJamie]

Im betting that the pump is not getting enough water.
I know you said you eliminated starvation issues, but thats still my bet.

 

[pcb]

Have you checked the valves in the pump? I've had problems from time to time where it will run fine on rinse because it's pressurized coming from city, but on soap and wax it's drawing from the tank. I would check for a broken o ring on the valve.

 

[2Biz]

If your pumps are drawing from a hot water gravity tank, have you checked to see if there is a CV inline between the pump and the water supply? Maybe its sticking and not allowing water flow when soap and wax are selected? Or is there a valve that restricts hot water flow so soap and wax draw into the pump? These two items can/maybe cause restriction and cavitation. Also Randy suggested you disconnect soap and wax from the pump....You have to switch to soap and wax and draw from the gravity tank to see if water supply is the issue before ruling it out. If you are using a 3/4" hose to each pump, this size hose does not create enough vacuum to draw soap and wax, so I would think there would be a valve to throttle water flow to get the right vacuum to draw soap and wax. This is another possible culpret...I had gate valves all over my old pumpstand to regulate flow so wax and soap would draw. Almost every single one had stems broke/rusted off so there was no adjustment! Just a few more things to try or look for if you haven't already. I don't suspect pump valves if it runs ok on city fed pressure for rinse.

 

[CWdummy]

What does "Yes" mean? Does it mean that your going to try that suggestion or does it mean that you've already tried that suggestion?

I answered his question “yes”.

 

[CWdummy]

OK. PROBLEM SOLVED.
Check valve was first thing I had previously checked. It was good. I did as Randy suggested and removed both wax and soap lines and capped tee below check valve at pump where the lines attached. No improvement. I removed all fittings and screwed a 3/4 elbow in pump with flare fitting and directly attached water supply. Worked perfectly!! Now I’m making progress. Everything I had taken off to bypass, I took apart, cleaned, re taped and reassembled. Everything working fine now. My assessment is the teflon tape had broken down over 35 yrs in one or several of these joints that had never needed to be taken apart. I say this as the old tape remnants were very thin and clear with no color. I am confident this was the problem. On rinse in any of the bays, everything runs smoothly. When I select soap or wax on any bay, there is a VERY small amount of vibration. Is this normal?
Thanks to everyone for your comments and interest in this crazy problem.

 

[Greg Pack]

Glad you found it. There is always those problems that make you scratch your head. I have some additional vibration in mine when they are drawing water as opposed to being pressure fed also. If you have the supply gated off in an effort to draw chemicals better open it up and see if it goes away. If it does I'd readjust chemicals to work with the valve open. I know many people keep their ball valves partially closed to draw chemical better but I found if I make my product (soap, wax)strong enough in the tank it's not necessary and better for the pump.

 

[CWdummy]

Greg,
Thanks for your response. My soap and wax lines are 1/4” and valves are wide open. No problem drawing chemicals if everything is working correctly. I keep a larger than recommended tip in my hydrominder. I have learned in 30 yrs of carwash ownership the customer subconsciously would rather see a soap show than have a better cleaning product.