Water pump short cycling, how to fix

deltabravo wrote:

Lectric80 wrote:
It doesn't matter which faucet I'm using, the pump cycles on and off about every 2-3 seconds, creating a surge-fade cycle.

An accumulator fixes the problem. I've used one in all my RVs since 2003.

Here's a video of the last one I installed

It is in the future plans for the unit, but right now getting the adjustment made to the pump has solved the issue.

Lectric80 wrote:
It doesn't matter which faucet I'm using, the pump cycles on and off about every 2-3 seconds, creating a surge-fade cycle.

An accumulator fixes the problem. I've used one in all my RVs since 2003.

Here's a video of the last one I installed

Spent 4 days on the property and made the adjustments. First thing to note, this pump is just a simple Phillips screw to adjust. Second, yes it was the issue, shower runs great now. Overall I had to add about one and a half turns, but pump runs great now.

Thank you everyone for the advice.

This is a Suburban water heater, but the anode was out when I bought it and brought it home. The anode was very clean and I did rinse the water heater prior to installing it.

Having watched a few videos on adjusting the pump, I'm certain it is the issue. The trailer was owned by a family association and based on the documentation left in the trailer, they weren't the most technically inclined. I bought from Camping World, so they do nothing with used units. So I'll try adjusting when I'm back at camp this weekend. I'll report back with findings, but it seems like the simplest solution for the time being.

The above reply by wa8xym describes the loss of air cushion in your water heater and where my thought process was headed on your pump issue. When the air cushion is lost, the freshwater system is jammed full of water with no room for heat expansion when the water is heated. When the heater starts up, the pressure can build close to 150 psi and trip the safety relief valve to weep off the excess expansion pressure. If this happens, you can see calcium and mineral buildup on the relief valve discharge port from the weeping. This high pressure will drop off instantly when a faucet is opened as that action burps the system.

Even when the system is cold, if and when the air pocket is gone, even without heating the water, the pump has to hit a dead-end filled system and can trip the pressure switch on the pump.

Is your water heater a Suburban or an Atwood? The Atwood is easy to put a drain valve on; the Suburban, which uses an anode in the drain port, makes it complex to add a drain valve. Even Atwood/Domentic discusses the air cushion loss and relief valve weeping in the heater instructions of the more modern heaters. Your 2004 manual may or may not mention it. Finally, the new Dometic redesigned water heater instructions talk about adding an expansion tank to cure the issues. They did not supply the expansion tank, they tell you to add it.

This is an age-old issue in the RV industry. If they would add an expansion tank from day one, the problem would not exist until the bladder leaked in the accumulator then there is no expansion left once again

Hope this helps and let us know how this comes out. Check your relief valve on the water heater for mineral buildup also.

John

Routine maintenance of the water heater.
Turn off water to the heater. Either turn off pump and city water or use heater bypass valves.

Remove drain plug and replace with a short length of 1/2 inch Pipe.. Plastic or metal does not matter.

Manually open TPR valve (the thing at the top on the otside of the thing

STAND BACK you will get wet and if it's hot water it's not fun.

Once it's drained flush out as much curd as you can flush out (use one of those flusher tools.. You may need to remove the pipe less you used thin wall tubing.)

Replace plug. if it's a anode inspect and replace with new if needed..

Open the valve you closed to cut off water and see if it helps. NOTE if using pump iot will run for some time re-filling heater.

This may solve short cycling. If it does I can explain why

With that symptom you don't have a leak and there's nothing wrong with the pump. You just need to adjust the pump and as mentioned before, there are some very good vids on Youtube.
Why they don't pre-adjust these pumps is beyond me but they often need adjustment by the end user.

WNYBob wrote:
Check out "attenuators" they use a compressed air pocket to smooth out the pressure. It can also provide a short time of pressure for those late night trips.
You splice it in line after the pump.

This is the accumulator I mentioned, and might be another option. I'll try adjusting first, then use this if needed.

WNYBob wrote:
Check out "attenuators" they use a compressed air pocket to smooth out the pressure. It can also provide a short time of pressure for those late night trips.
You splice it in line after the pump.

X2

Check out "attenuators" they use a compressed air pocket to smooth out the pressure. It can also provide a short time of pressure for those late night trips.
You splice it in line after the pump.