How pumps work / Diagnosis question about backfeed

[cityview]

I've had this problem happen a three times now over a couple of years The first two times on different pumps, I fixed it by replacing EVERYTHING (lines, regulators, solenoid valve, etc) because I have no idea how these actually work, and don't want down time. My first thought is it would be the solenoid valve, but I tried fixing that the first time and that didn't solve it.

So I thought this time since I can't order anything until Monday anyway, instead of just replacing each part, I'd get on here and ask which part is actually the one failing?

When High Pressure is on, I get high pressure out my low pressure presoak input hose. Its not "full" high pressure, but its enough to blow the plastic line.

(In the attached image, it is the RED line that breaks)

Bonus points if anyone can clarify how water actually flows through these lines. I looked at the diagram for the pump and it seems like there's water going in the out lines and out the in lines... I figured if I could figure out how they actually work, diagnosis would be common sense.

Thanks for the help!

 

[2Biz]

Your problem is most likely the CV in the manifold above the bay that keeps HP from back feeding into the PS line. The CV isn't completely bad, but sounds like it lets just enough HP to blow past the seat that it either ruptures or blows off the PS line at the pump. LLDPE tubing that is used on the PS is only rated for about 230psi @ 70°..So it doesn't take much pressure to rupture it. Change the CV on the PS above the bay and I bet it will solve your problem.

 

[MEP001]

The silver cylindrical regulator is your main regulator. The solenoid on the left is a DEMA 453P, and (I'm assuming by your description) it opens when presoak is selected to reduce the pump pressure through the other regulator below the solenoid. If pressures are doing what they're supposed to, the regulators aren't the problem. I can immediately think of two possibilities, either the pump is pulsating and causing shock to the tubing making it break, or when the pump shuts off the pressure in the line to the bay is coming back through the pump and bursting the tubing.

 

[Jeff_L]

Simply put a check valve between the push lock fitting and the cross to prevent the PS bypass from going into the red poly hose.

 

[MEP001]

 

[cityview]

Thanks!

Between you adding to my drawing and the description from MEP001 I feel more confident at least in what is happening. Thank you.

 

[cityview]

Simply put a check valve between the push lock fitting and the cross to prevent the PS bypass from going into the red poly hose.

I thought about that as a short term solution, but I fear that is simply covering up the real problem, and what I've found in my experience is covering up the real problem with a short term fix, typically that just causes a bigger problem down the road!

 

[cityview]

Your problem is most likely the CV in the manifold above the bay that keeps HP from back feeding into the PS line. The CV isn't completely bad, but sounds like it lets just enough HP to blow past the seat that it either ruptures or blows off the PS line at the pump. LLDPE tubing that is used on the PS is only rated for about 230psi @ 70°..So it doesn't take much pressure to rupture it. Change the CV on the PS above the bay and I bet it will solve your problem.

Thanks for your response. Can you help me understand this a little further?
I don't have any check valves on my HP lines. The check valves on my LP lines have failed before, which causes ruptures in my LP lines, but the PS line doesn't go to the manifolds... it just goes through the HP line. therefore I'm not sure what CV could be failing to be causing an issue back by the pump.

 

[cityview]

The silver cylindrical regulator is your main regulator. The solenoid on the left is a DEMA 453P, and (I'm assuming by your description) it opens when presoak is selected to reduce the pump pressure through the other regulator below the solenoid. If pressures are doing what they're supposed to, the regulators aren't the problem. I can immediately think of two possibilities, either the pump is pulsating and causing shock to the tubing making it break, or when the pump shuts off the pressure in the line to the bay is coming back through the pump and bursting the tubing.

Thanks for the description and for weighing in. That is helpful to understand.

The high pressure out the LLDPE is happening while the gun is spraying high pressure. I disconnected it and ran some cycles out the bay gun. When the HP is on, I get higher than normal pressure coming out that line, enough to create splits in the line and/or leak/pop off at the connection points. When the gun is off, I get a trickle out of all my PS lines. It is constant high when the meters running. It does not happen when the pump shuts off, and is not related to pulsating. At this exact moment, I left a split in the line so when the HP is on, I get a controlled "relief valve" leak out the LLDPE. I'm going to stick a check valve there tomorrow until I can fix it, but I didn't want to lose out on having a bay shut down right now when I could make it work.

 

[MEP001]

I thought about that as a short term solution, but I fear that is simply covering up the real problem, and what I've found in my experience is covering up the real problem with a short term fix, typically that just causes a bigger problem down the road!

I'm the same way, I can't tell you how many washes I've been in where someone kept adding check valves to the point they had more problems with check valves than they had before they added them trying to fix the issue with check valves.

If you're willing to try an experiment, maybe disconnect the high pressure regulator's bypass line where it goes back into the pump, plug the fitting and run the pump with the bypass hose into a bucket or something and see if you're still getting that pressure from the tubing line. The fitting could be restricted from something and the bypass water would blow the tubing as it's the weakest point.

 

[2Biz]

Thanks for your response. Can you help me understand this a little further?
I don't have any check valves on my HP lines. The check valves on my LP lines have failed before, which causes ruptures in my LP lines, but the PS line doesn't go to the manifolds... it just goes through the HP line. therefore I'm not sure what CV could be failing to be causing an issue back by the pump.

Sorry, I've never seen or heard of a system where the PS goes through the HP pump....Most of them I've seen uses a Flojet or Rotary Pump that tee's the LLDPE tubing in a manifold above the bay with a CV at the manifold that keeps HP from back-flowing...Yours is totally different...

I had issues of back-flowing PS years ago from the HP gun. To eliminate this issue for good, I put PS on the foam gun along with TF...This eliminated a dozen C/V's in the attic...Air and liquid with backup C/V's for a 4 bay... Now I only have (4) SFR C/V's in the attic...And (4) C/V's for weep.......Life is good now!

 

[Jeff_L]

If the return from your bypass regulator for your personal is at a higher pressure than what your red poly line can handle, then putting a CV there isn’t a temporary fix, it’s necessary. Perhaps you can reduce the pressure from your PS bypass to something less than the rating on your your poly line. But that impacts your customer experience in the bay.

 

[mac]

2Biz has it right. That is what's causing this.

 

[Jeff_L]

I bought a wash that was set up that way for PS. I wasn’t a fan of it and moved PS over to a Procon pump.

 

[MEP001]

If the return from your bypass regulator for your personal is at a higher pressure than what your red poly line can handle, then putting a CV there isn’t a temporary fix, it’s necessary. Perhaps you can reduce the pressure from your PS bypass to something less than the rating on your your poly line. But that impacts your customer experience in the bay.

In theory there shouldn't be any more pressure there than the gravity feed from the tank, but my guess is the flow from the regulators through a restriction is causing pressure to build. Either way, a check valve should fix it, but it needs to be one with a low cracking pressure. Another option would be to move the presoak line to the same tee where soap and wax enter the line.

 

[MEP001]

2Biz has it right. That is what's causing this.

From this post?

Your problem is most likely the CV in the manifold above the bay that keeps HP from back feeding into the PS line. The CV isn't completely bad, but sounds like it lets just enough HP to blow past the seat that it either ruptures or blows off the PS line at the pump. LLDPE tubing that is used on the PS is only rated for about 230psi @ 70°..So it doesn't take much pressure to rupture it. Change the CV on the PS above the bay and I bet it will solve your problem.

OP's presoak is run through the high-pressure pump at a reduced pressure. It doesn't tee into the boom, it uses the same high-pressure line.

 

[cityview]

I'm the same way, I can't tell you how many washes I've been in where someone kept adding check valves to the point they had more problems with check valves than they had before they added them trying to fix the issue with check valves.

If you're willing to try an experiment, maybe disconnect the high pressure regulator's bypass line where it goes back into the pump, plug the fitting and run the pump with the bypass hose into a bucket or something and see if you're still getting that pressure from the tubing line. The fitting could be restricted from something and the bypass water would blow the tubing as it's the weakest point.

I meant to get to this today but had something else pressing came up. I'm going to play with this next time I get out there. Thanks for the thoughts!

 

[cityview]

If the return from your bypass regulator for your personal is at a higher pressure than what your red poly line can handle, then putting a CV there isn’t a temporary fix, it’s necessary. Perhaps you can reduce the pressure from your PS bypass to something less than the rating on your your poly line. But that impacts your customer experience in the bay.

But I have 5 bays over 20 years that operate without it... and there is only one pay that pushes high pressure out that poly line, which just started this week. I can do a CV temporarily, but its not necessary.

 

[cityview]

In theory there shouldn't be any more pressure there than the gravity feed from the tank, but my guess is the flow from the regulators through a restriction is causing pressure to build. Either way, a check valve should fix it, but it needs to be one with a low cracking pressure. Another option would be to move the presoak line to the same tee where soap and wax enter the line.

The whole setup seems odd to me to start with... I don't really understand why I have a Flojet pumping presoak into the LP line at the pump, but I guess it does work.

I might settle for a CV, but It seems a bit hacky to me since it works fine, and I'm guessing its a precurser to a regulator failure or line restriction.

Thanks for the thoughts!

 

[MEP001]

The whole setup seems odd to me to start with... I don't really understand why I have a Flojet pumping presoak into the LP line at the pump, but I guess it does work.

You wouldn't usually have a Flojet pumping soap into the pump, but maybe someone wanted it stronger and figured that was the only way to get enough soap into the inlet. Or maybe they thought it would get to the bay faster.