Knocking during wash phase

[Faceonglass]

During the wash phase on one of my bays, something causes knocking and the output pressure is lower than normal. This also happens during the wax phase.

The rinse phase is normal and gives out correct pressure. I sometimes wish I knew what I was doing, but I kind of inherited this problem.

Any ideas on the first place to look for the problem?

 

[Randy]

It sounds like your starving the pump for water during those 2 cycles or your sucking air. If you don’t fix it right away you’ll be buying a new pump, pump cavitation and air leaks will ruin a pump head pretty fast. Verify that you’re getting water to the pump during those 2 cycles.

 

[Faceonglass]

It sounds like your starving the pump for water during those 2 cycles or your sucking air. If you don’t fix it right away you’ll be buying a new pump, pump cavitation and air leaks will ruin a pump head pretty fast. Verify that you’re getting water to the pump during those 2 cycles.

Well, I have it shut down and I am fairly sure it started either today or yesterday.

Alright, now I see where the water feed for those two cycles comes in and they are both using the same source. It runs through a solenoid and a backflow valve. So I am guessing one of those is the source of my problem.

It seems the solenoid not opening up all the way makes the most sense, does that sound logical?

P.S. thanks for the reply, just texted in a $10 donation to the quake relief in your honor!

 

[Randy]

It’s probably not the backflow valve. The first thing I’d check for would be to see if there is power to the solenoid valve then I’d check for any debris in the inlet of the solenoid valve. My pumps are fed with city water pressure, to get the pumps to draw chemical there is a pressure regulator on every pump. This eliminates the troublesome water supply tank that always seems to overflow. If you have a pressure regulator check it for debris in the inlet. I have a screen on my water inlet.

 

[Faceonglass]

It’s probably not the backflow valve. The first thing I’d check for would be to see if there is power to the solenoid valve then I’d check for any debris in the inlet of the solenoid valve. My pumps are fed with city water pressure, to get the pumps to draw chemical there is a pressure regulator on every pump. This eliminates the troublesome water supply tank that always seems to overflow. If you have a pressure regulator check it for debris in the inlet. I have a screen on my water inlet.

Pretty sure it is the solenoid that is the issue. I just took the thing off the stem and tried it and it did the same thing.

Still a little bit too much a novice to be messing around with the electric and the only way to switch it out with the electric off is to shut down all the bays. Going to have to wait until tonight to do that and see if it is a bad solenoid or an electrical issue.

I would rather not have to call in an electrician, so hopefully it is the solenoid.

Anyway, thanks again!

 

[MEP001]

Since you get a knocking on soap and wax but not rinse, your solenoid is likely not the problem. Typically the rinse solenoid feeds water to the pump at city pressure, and with soap and wax it's drawing from a gravity-feed tank. The check valve on that line from the tank could be sticking or restricted and causing your problem.

I've seen once where the bolts on a piston pushrod managed to work loose - the pump ran normally on rinse because the water pressure held the piston against the crankshaft, but on soap or wax it would knock and pulsate badly.

 

[dogwasher]

Mep, my cat pumps always knock when the automatic is in the spot free mode. I was told that it was the spot free water causing this, is this true?

 

[JMMUSTANG]

I agree with MEP001 but I also had a similiar problem that happened to be my fault.
Years ago I had to use a galvanized fitting for a quick fix, because the local hardware store did not have a brass fitting, figuring I'd change it out later. Forgot all about it and it eventually it clogged starving the flow from the tanks causing it to knock.

 

[MEP001]

Mep, my cat pumps always knock when the automatic is in the spot free mode. I was told that it was the spot free water causing this, is this true?Mep, my cat pumps always knock when the automatic is in the spot free mode. I was told that it was the spot free water causing this, is this true?

Does the spot-free get pumped with the high-pressure pump but with a pressure reducing valve? I seriously doubt it's the water, especially if it only does it if the auto bay is pumping spot-free at the same time. That sounds more like undersized plumbing to the pumps, or something with the automatic pump's plumbing that's aerating the water when it's running.

 

[Faceonglass]

Thanks for all the replies, I managed to get it working normally again today.

The good news is I learned alot about my self serve today. The bad news is what fixed it just seemed completely illogical to me and was very easy to do. The fix was accomplished after completely dismantling everything, and I mean everything looking for the cause.

The screen at the bottom of my soap tank had a bolt in it. I am not sure where the thing came from, it was just there. What really baffles me is how this managed to cause problems with a single pump instead of all of them and why it also caused problems with the wax setting. It just makes absolutely no sense whatsoever and is why I did not look there in the first place.

Anyway, if anyone can make heads or tails of why that happened, I would really like to hear it.

All I know is I checked everything and it was still messing up. I then reached my hand down into hot soapy water, felt around, and came up with a bolt. Went and tried one more time and the damned thing worked normally.

 

[dogwasher]

Does the spot-free get pumped with the high-pressure pump but with a pressure reducing valve? I seriously doubt it's the water, especially if it only does it if the auto bay is pumping spot-free at the same time. That sounds more like undersized plumbing to the pumps, or something with the automatic pump's plumbing that's aerating the water when it's running.

My spot free Cat pumps (3) PULL the water from the underground tank,
I would say the run of tubing(each pump has its own run) is about 8' long and about a 4' vertical run.

 

[Randy]

I knew it was going to be something very simple, 9 times out of 10 it is. Just consider it a learning experience or a hands on educational training session. Get yourself a volt meter and learn how to use it. It’ll be one of the best tools you can have owning a car wash.

 

[MEP001]

My spot free Cat pumps (3) PULL the water from the underground tank

Cat pumps require the plumbing to the pump be flooded; they don't have a rating for head lift. I would recommend a small tank kept full by another pump rated for lifting water for the Cats to draw from.