Water pump keeps cycling on.

[Hoohaa]

We have two identical tanks and fresh water systems in our catamaran. Port and Starboard.
No accumulator tanks.
The only difference is a 15 litre hot water heater on Starboard.
The Starboard pump cycles on with a short burst every couple of minutes.
There are no evidence of any leaks. The boat is only 4 year's old.
Any ideas on what could be causing it?

[GreenWave]

Likely your water heater does have a leak tho minuscule. Are you able to see all sides and all connections?

[Hoohaa]

I can't see all sides. But it's very clean and definitely no moisture anywhere in the bilge underneath the unit.
I was thinking that the heater would have a pressure relief valve. Maybe that is allowing a small escape.

[GreenWave]

Originally Posted by Hoohaa

I can't see all sides. But it's very clean and definitely no moisture anywhere in the bilge underneath the unit.
I was thinking that the heater would have a pressure relief valve. Maybe that is allowing a small escape.

That is a very plausible theory. Might be worth pulling it and replacing the valve.

[Putt-Putt]

You may want to try this, no cost but some labour involved, test.

Flip the pumps from Port to Starboard, if they are identical it should not be too hard to do.

If the problem follows the Starboard pump, bingo, thats your problem.
Pumps can leak internally, or just have sensor problems.

If the problem stays on the Starbord side, the list of potential things grows long.

Should the pressure relief valve on the water heater prove to be the culprit, (which I doubt) the fitting of an expansion (accumulator) tank would solve the problem. I'd be surprised if you don't already have one.

[Bowdrie]

Originally Posted by Hoohaa

I can't see all sides. But it's very clean and definitely no moisture anywhere in the bilge underneath the unit.
I was thinking that the heater would have a pressure relief valve. Maybe that is allowing a small escape.

So there is definitely no moisture anywhere, but you think the relief valve is releasing water?
That doesn't add up.
When the water is heated it expands, if there isn't any place for it to go it can build up high pressure which puts a heavy load on the plumbing/fixtures.
Is there an inlet check valve on the heater?
The good ones have short life spans, the cheap ones are junk.
With an accumulator tank and no check valve any expansion of the water is simply accommodated by the expansion tank and it works well.
Without a check valve or an accumulator tank the increase in back pressure from the heated water is constantly trying to back-flow thru the pump.
The pump valves work pretty good under standard pressure, they are not designed to constantly withstand the pressure in a system in which the pressure relief valve on the water heater will release.
If the pump cycles it's because the pressure has dropped below the cut-in pressure, that's not a small amount.
A temperature/pressure relief valve that's releasing water is NOT a normal operation of a hot water system.

[wholybee]

Originally Posted by Putt-Putt

You may want to try this, no cost but some labour involved, test.

Flip the pumps from Port to Starboard, if they are identical it should not be too hard to do.

If the problem follows the Starboard pump, bingo, thats your problem.
Pumps can leak internally, or just have sensor problems.

If the problem stays on the Starbord side, the list of potential things grows long.

Should the pressure relief valve on the water heater prove to be the culprit, (which I doubt) the fitting of an expansion (accumulator) tank would solve the problem. I'd be surprised if you don't already have one.

This. The pumps have a one-way check valve inside them. If that valve starts to leak, the pump will cycle, even with no external water or air leaks.

[neflier]

Had the same problem on my prior boat. The pump cycled every few minutes with no evidence of a leak. I did a deep dive in the pump's manual and it said to clean the filter on the inlet side. Skeptically I did, it was filthy, only took a few minutes and the problem was solved.

[Hoohaa]

Some great advice guy's.
I'll work through them.
Another thought. The pump cycles even when the water heater is cold.
Definately dry underneath.
I'll let you know the outcome.
Jeff

[sailorboy1]

It is almost always the pump if you can not find a dripping outlet.

Open all the outlets in the loop and let it flush and maybe whatever has a valve back leaking will flush out.

The other thin g that normally works is to buy and have a spare pump. Then the installed pumps never go bad

[Scrimshaw4]

I had same problem. It was the check valve in the water pump that allowed back pressure to force ater back to the gtank reducing the line pressure. Try this. Between cycles, close the supply line from the tank to the pump. The pump may cycle once, but after that there shoudn't be any more cycling if it's the pump valve.

[Hoohaa]

Sorry for the delay in getting back to this problem.
Today I got around to pulling the pump apart and taking a few pins.
I did find a small plastic shaving in the small pressure switch?
I'm not shore of the correct part names. I've googled Manuel but the part schematics number the parts but leave out the table's to show what the parts are called. Very frustrating. I must be missing something.
Here's some pics.
By the way the problem still exists.
[ATTACH][ATTACH][ATTACH][/ATTACH][/ATTACH][/ATTACH]

[Hoohaa]

Originally Posted by neflier

Had the same problem on my prior boat. The pump cycled every few minutes with no evidence of a leak. I did a deep dive in the pump's manual and it said to clean the filter on the inlet side. Skeptically I did, it was filthy, only took a few minutes and the problem was solved.

Was this filter part of the pump or inline before the pump?

[Lepke]

One way to fix is to put a check valve between pump and tank. Close to the pump is better.

[TheBadger]

I had same issue. It was the transom cold shower leaking. The water went overboard, no bilge water to see...