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Water pump cycling intermittently


RaderNed

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Are there causes for the coach water pump cycling when the system's not in use (no tap open, not flushing toilet, etc) other than leaks in the system? My pump does this somewhat intermittently. For instance, about 90% of the time, within 30 seconds after I've closed a tap or completed a flush, the pump will give one very brief grunt. About 50% of the time, between 3 and 5 minutes later, it'll give another grunt. Sometimes, but rarely, it'll grunt again 5 minutes later. After that, it doesn't happen again. I can (and have) leave the pump on all night and it won't grunt again. If its has its first grunt or two, I can turn it off over night and it won't grunt again when I switch it on in the morning. 

Other than one short section that runs behind the fiberglass bathroom unit wall, I've checked all the piping and connections and they're bone dry. I've checked the drain tubes coming from the system drainage valves, and they'd dry. I've checked the pump and the floor under the pump, and it's dry. I have checked the plumbing going into the water heater, and checked in, around and under the compartment it's in, but I haven't pulled the heater all the way out. 

I'm stumped! 

I did drain the system last year, is it possible there's an air bubble in there somewhere that's causing this? I've used all the taps since then. 

 

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Ok the pump is unlike some thing you may find in a house. There is no air cushion and water does not compress so a tiny leak will drop the pressure enough for the pump to come on. The hot water tank is suspect as are any drain valves you may have. In this case an air pocket might actually help.

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There is a oneway check valve in the pump it might take a few "blasts" to get it to seat, an old pressure switch. An old pump.  Or its normal, stop worrying. A leak usually shows up as the pump cycling through the night

 

This is an accumulator tank for the water system, the built-in air pocket.  https://www.pplmotorhomes.com/parts/electrical-plumbing-lp-gas/rv-pumps-water-filters-fixtures/water-pump/water-pump-tank_86-8139

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6 hours ago, WME said:

There is a oneway check valve in the pump it might take a few "blasts" to get it to seat, an old pressure switch. An old pump.  Or its normal, stop worrying. A leak usually shows up as the pump cycling through the night

 

This is an accumulator tank for the water system, the built-in air pocket.  https://www.pplmotorhomes.com/parts/electrical-plumbing-lp-gas/rv-pumps-water-filters-fixtures/water-pump/water-pump-tank_86-8139

Thanks, that's reassuring. I figured it has either something to do with the pump, switch or maybe toilet valve. I replaced the toilet valve not too long ago so probably not that. 

 

Liked that link, too. Thanks! 

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If the pump is left on and it cycles often with no water used it has a leak some where there should be enough trapped air to maintain pressure enough for the pump not to cycle. I have a 2 gallon air tank in my camper if it sits for a month or more I still have water pressure with the pump off and more often than not the pump does not come on for a couple of minutes later so the system is vert tight. The most over looked leak is the hot water tank because it is hard to see the tank and they a generally are small leaks to start with. It is some thing that needs to be checked if your pump is cycling or you will end up with a rotted floor. Yes maybe it is the pump valves leaking but that usually causes low water pressure also. I don't know where your tank is but my Nova Star was under the closet floor I had to remove it to have a look and yes it was leaking. 

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A weird low probability thing is a waterlogged heater.  When you summerize your MH you should trap an air bubble in the water heater. Close the drain valve and the pressure release valve at the same time. The pump will fill the heater and there will be the bubble at the top. This lets water expand when it gets hot and helps regulate stable pressure.

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13 hours ago, Maineah said:

If the pump is left on and it cycles often with no water used it has a leak some where there should be enough trapped air to maintain pressure enough for the pump not to cycle. I have a 2 gallon air tank in my camper if it sits for a month or more I still have water pressure with the pump off and more often than not the pump does not come on for a couple of minutes later so the system is vert tight. The most over looked leak is the hot water tank because it is hard to see the tank and they a generally are small leaks to start with. It is some thing that needs to be checked if your pump is cycling or you will end up with a rotted floor. Yes maybe it is the pump valves leaking but that usually causes low water pressure also. I don't know where your tank is but my Nova Star was under the closet floor I had to remove it to have a look and yes it was leaking. 

I'll take a closer look at the hot water tank just to be sure, but no obvious signs of leakage around it or under it (looking at the floor under it from beneath the rv). Thanks for the tip 

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11 hours ago, WME said:

A weird low probability thing is a waterlogged heater.  When you summerize your MH you should trap an air bubble in the water heater. Close the drain valve and the pressure release valve at the same time. The pump will fill the heater and there will be the bubble at the top. This lets water expand when it gets hot and helps regulate stable pressure.

That's an interesting possibility as I didn't do that when I filled and started the system last time. Do I need to drain the heater tank to do that now? Or the whole system? 

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8 hours ago, Gulfstream Greg said:

I'm putting my money on the pump check valve

The fact that the pump stops cycling after one to three times makes me lean towards the check valve too. If it was a leak, seems like it would continue to cycle, and there'd be pretty obvious water somewhere 

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1 hour ago, RaderNed said:

The fact that the pump stops cycling after one to three times makes me lean towards the check valve too. If it was a leak, seems like it would continue to cycle, and there'd be pretty obvious water somewhere 

I think the valves can be purchased to repair the pump. Google the brand, model and valve etc. Cheaper than a new pump

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5 hours ago, RaderNed said:

That's an interesting possibility as I didn't do that when I filled and started the system last time. Do I need to drain the heater tank to do that now? Or the whole system? 

Shut off the pump and open the drain valve and let out a few cups of water. Close the drain valve and let the pump refill the tank and your golden.

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There are valve kits available for most pumps it's not a hard job it will hurt nothing as long is there are no leaks. The biggest problem with no air in a hot water tank is a leaking over pressure valve because the tank is over filled this can cause your pump to cycle. Turn off the pump turn on a hot water tap or two till the water stops running  open the over pressure lever on the water tank for a bit close the over temp lever and the taps turn the pump back on.

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my guess is a dripping faucet - put a bowl under all your faucets - including any outside shower.  

btw, I do leave my water system pressurized except when I am actually using it.

Also, of you do identify a dripping faucet, remove the knob & outer works, turn on the water pressure for a short blast - one little piece of sand or grit can be the source.

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16 hours ago, Maineah said:

There are valve kits available for most pumps it's not a hard job it will hurt nothing as long is there are no leaks. The biggest problem with no air in a hot water tank is a leaking over pressure valve because the tank is over filled this can cause your pump to cycle. Turn off the pump turn on a hot water tap or two till the water stops running  open the over pressure lever on the water tank for a bit close the over temp lever and the taps turn the pump back on.

Thanks, I'll look into that 

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14 hours ago, DanAatTheCape said:

my guess is a dripping faucet - put a bowl under all your faucets - including any outside shower.  

btw, I do leave my water system pressurized except when I am actually using it.

Also, of you do identify a dripping faucet, remove the knob & outer works, turn on the water pressure for a short blast - one little piece of sand or grit can be the source.

Thanks, I've done that but doesn't seem to be it 

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Just turn the pump off unless your going to use it. I never leave my water pump on. Pipe splits when your not paying attention or out of the RV can be a disaster. Unfortunately leaks are never where they would be an easy fix. Mine started leaking behind the rear dinette where the pipes cross over to the bathroom. I was able to catch it almost immediately though cause I knew something was wrong right after I turned the faucet off. If your on the road and use it this way you will be able to wait until you get somewhere you can really check it out. My friend Tony has lived his entire adult life on a boat or in an RV. His kids were raised knowing to always turn the water pump off. 

Linda S

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Yeah, I don't normally leave it on, and I'm pretty confident there's not a leak, it's just one of those niggling little issues I'd like to take care of. 

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Maybe the easiest solution! 

15 hours ago, linda s said:

Buy a new pump. Your probably due anyway. Not that expensive and easy to switch out. If there is really no leaks the problem should be gone

Linda S

 

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i do as linda s explained, i only turn my pump switch on when i want to open a water valve (kitchen sink, bathroom sink, shower, or toilet), but just to educate me, IF i left the water pump switch on continuously, would it be usual or normal to have the water pump cycle WITHOUT opening a water valve , or would/should the pump only cycle when opening a water valve.   thanks for answering anyone. joe from dover

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No it shouldn't cycle. It has a pressure sensor that stops it. If the pressure goes down it will cycle but that means the pump isn't sealed properly, look at all the valve comments,  or the water is going somewhere, aka leak. 

Linda S

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It's not a real good ideal to leave the pump on no matter how tight your system is you may come back to the entire water tank contents on your floor. Seen people walk away from their campers too hooked up to city water with out turning the tap off. They are not like a house where the plumbing is not subject to vibrations from a moving house. Campers in general do not use the very best plumbing fixtures either most are usually plastic. The electric pump are in the 25 PSI range max pressure, the switch  differential is probably in the 15 pound range. 

Edited by Maineah
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Maineah,

Great tip on turning off the city water when leaving your RV at a campsite.  Though I've always turned off the pump switch when I'm not using water during dry camping, I had never thought about turning off the city water when we're away from our RV. Sometimes we think we're so smart about things and then someone like you reminds us we still have allot to learn.  Thank you for ALL your excellent advice on these forums.

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I don't know about others m y 1978 and my 87 have had                           both  will sometimes cycle maybe one clunk now and then . when the water tank gets down to about half.  and the 78 had no water heater . and both have  had                   no leaks. did that even with a brand new pump. but they have only done it when the tank was down some.

Edited by 5Toyota
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If the pump is left on for extended periods yes it's likely cycle it is the air dissolving into the water. As you probable have seen when you turn a tap on with the pump off there is very little water delivery because the pressure drops to zero with no air pressure. Water does not compress so there is nothing to force the water out. I have a 2 gallon air tank in my camper plumbing the water will run at least 2 minutes before the pump comes on. 

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that 2 gallon air tank you have is an interesting idea .just like a house pump tank. must save some wear on your pump ,and battery draw. have you ever seen one of those old time campers with an air  pump     pumping air into a metal water tank. my frend had a 1969   with that . maybe after 2 days they would pump a little more air in great pressure. come fall they just blew it out with that  worked great . had an old time no battery need ed heater gravity unit really put out the heat . as a handy man do you miss the old radio shack I mean before it went in the tolit . I do .

Edited by 5Toyota
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