Waterpump cycling

[geoffr]

Our water pump is running every so often (at night mainly it seems) even when the taps haven't been using for a while. I have been checking for leaks but haven't found one. Has anyone else had this problem and found a solution?

This is a new problem - the pump wasn't doing this before...

Pump is a Jabsco WPS 4.0
Accumulator is a Jabsco 65L (30573-0003)

[rtoner]

Leaks are hard to find. Is your bilge dry? If not, is it fresh or salt water. I had a connector slowly leaking and only found it by putting paper towels under it. I guess the amount of water was evaporating quickly enough that prevented me from feeling the wetness.

[geoffr]

Bilge is dry, that was the first thing I checked

A leak was my first thought, but I haven't found it... and normally for the pump to kick in you need to fill more than a cup of water.. so I would have thought I'd see it. (but I'm not totally discounting a leak)

[hlev00]

We had the same problem. I replaced the pump and kept the original as a spare. The problem went away. My understanding is that if there is no leaking downstream that the problem is caused by water slowly leaking back through the pump. Try using the google search on this forum. You will find many similar threads.
Harry

[Rumrace]

Accumulator is a must. We found our boat with the water system not winterized. Everything was shot on a low hour boat. The accumulator did survive as well as two water tanks. Not even the toilet avoided ice damage to the valve. Most boats I’ve bought didn’t have an accumulator but I’ve added them. You can get tiny dirt cheap ones for small boats but the larger ones with full sized kitchens and showers important. The accumulator is just a vessel with a one way valve. Without it the wearing part of your pump is holding water pressure. The water pressure slowly leaks by the worn rubber bits and “nnnnnnnnnnzt” wakes you up.
Our water pump is delayed sometimes never comes on with a short blast from a faucet. Installing an accumulator can mysteriously stop leaks and pumps live a full life.

[goboatingnow]

Does it cycle more if water is hot ?
( check the calorifier pressure release )

Agree over time pressure can release back through the pump and the pump cycles. Sometimes the pressure switch acts up

Accumulator will not prevent this

Once or twice in 24 hours ? Turn the stereo up.

[Rumrace]

With an accumulator in front of the pump there is no pressure on the pump at all.
Zero debate on accumulators absolutely no negatives not invented. It should be a part of your system. Every new boat every brand claiming to be a cruiser comes with one or more.
In the 80’s and part of the 90’s many power boat brands didn’t. The two speed pump was their solution and still is for some silly reasons and a couple good ones.
My accumulator is in the wall behind the dinette standard factor affaire on any brand in the Beneteau Group.

[rwidman]

If there are no external leaks, the water is leaking back through the pump's internal check valve.

You can try rebuilding the pump, but it's far easier to simply replace the pump.

A "hack" is to install an external check valve immediately after the pump.

[boatpoker]

Originally Posted by Rumrace

With an accumulator in front of the pump there is no pressure on the pump at all.
Zero debate on accumulators absolutely no negatives not invented.

The accumulator is fitted after the pump, not "in front" of it.

Its the pump that keeps the accumulator pressurized therefore there
is pressure on the pump.

[Bowdrie]

I've been on a couple of larger boats that had a "normally closed" solenoid valve between the pump and the accumulator tank.
When the pump turns on the valve opens, when the pump reaches its cut-off and stops the valve closes, thus the pump is never subjected to backpressure during the off cycle.
But with the small pumps/systems that most boats use it's generally an unnecessary complication.
Although, it's not a bad idea to have a ball valve on the outlet of the pump to allow service or removal/changing of the pump without dumping the system.
A 60>80 mesh screen strainer on the inlet side of the pump can eliminate stuff that tends to "hold open" the little disc valves in those "multi-chamber" pumps, which can cause short cycling.

[geoffr]

I took the pump apart the other day and found a hair wrapped in and around the membrane. Put the pump back together and all is working well now - It's not running at night any more

Thanks all for the advice!

[ItDepends]

Originally Posted by Bowdrie

I've been on a couple of larger boats that had a "normally closed" solenoid valve between the pump and the accumulator tank.
When the pump turns on the valve opens, when the pump reaches its cut-off and stops the valve closes, thus the pump is never subjected to backpressure during the off cycle.

That's about the silliest approach I have ever heard of. So much complexity, and so much to go wrong. As somebody who has designed mission critical, industrial plumbing systems if I had ever proposed such an design I'd have been laughed out of the building, and then locked out and not allowed back in.

[Bowdrie]

Originally Posted by ItDepends

That's about the silliest approach I have ever heard of. So much complexity, and so much to go wrong. As somebody who has designed mission critical, industrial plumbing systems if I had ever proposed such an design I'd have been laughed out of the building, and then locked out and not allowed back in.

It's not "silly" at all in larger systems.
A similar approach is quite common in larger refrigeration systems, (although the valve is placed between the accumulator and the TXV).
"So much complexity/so much to go wrong", give it a break, it's a simple valve wired in parallel with the pump.
One such boat was a 130' motor yacht, the other was a 120' motor sailor, they both had accumulator tanks that I would guess to be ~30 gallons, and they were not using some piddly Jabsco type pump.
And, had the OP have had an inlet strainer, (as I mentioned in post #10,) that hair most likely would not have caused a problem.
If you re-read my previous post, (perhaps more slowly,) you might see where I did say that in a smaller system such a valve was generally unnecessary.

[donradcliffe]

Sometimes small stuff can get through the strainer and cause the pump check valves to leak. I've had it happen to me. If there's nothing obvious, sometimes running your finger around the seat and valve surfaces of each check valve in the pump can displace the crud and solve the problem.

The problem with a solenoid valve in the system is that they can also leak. Bigger boats have big accumulators, and it can take hours to leak down far enough to make the pump cycle.

[Bowdrie]

Originally Posted by donradcliffe

Sometimes small stuff can get through the strainer and cause the pump check valves to leak. I've had it happen to me. If there's nothing obvious, sometimes running your finger around the seat and valve surfaces of each check valve in the pump can displace the crud and solve the problem.

The problem with a solenoid valve in the system is that they can also leak. Bigger boats have big accumulators, and it can take hours to leak down far enough to make the pump cycle.

You're right, the operative word being "sometimes".
Sometimes "anything" can happen.
We do the best we can with what we've got to work with, and sometimes it's good enough. and sometimes it isn't.