Water pump delay kicking in

[Capitana]

Hi folks,

While underway earlier in the week we sprung a nasty leak in the shower hose beneath our bathroom sink and the water pump proceeded to sneakily dump all 150ltrs of fresh water (via the hot water tank!) into the bilges. So that was a fun passage.

As a temp fix I've removed the tap fitting and hoses and blocked those off for now. Refilled the tank, the pump ran for a while as I assume it was filling the hot water tank again and refilling the system in general. Bled the air out. All seemed bueno!

When I run the cold water tap now the pump kicks in as usual. But not for the hot water tap. I have to run the cold tap as well for the pump to recognise I'm taking water out of the heater. Or if I run the hot water for a time, I then have to run a spot of cold for the pump to kick in and refill the hot water deposit.

Any ideas re troubleshooting? There's been air to bleed out of the lines as expected, but all seems to be out now. The pump isn't kicking in sporadically at all, so I'm not assuming any further leaks.

Welcome your thoughts. Cheers all.

[HopCar]

Air trapped in the water heater so it’s acting like an accumulator tank?

[chris95040]

So if you open a hot water tap, just a hot water tap, and -leave it open-, what exactly happens?

Based on your description it sounds like the flow will slowly drop to nothing and the pump will never come on?

[tkeithlu]

I immediately jumped to HopCar's hypothesis and wanted to recommend loosening the discharge hose on the heater, turning on the pump, and getting rid of the air. But, that really doesn't fit all of your description, as Chris95040 points out. He's taken your description to its logical end - the hot water faucet open, with no water coming out.

Do you by any chance have another place to hold hot water/air, as in another hot water faucet elseware in the boat, that you have not purged of air?

[Scubaseas]

While underway earlier in the week we sprung a nasty leak in the shower hose beneath our bathroom sink and the water pump proceeded to sneakily dump all 150ltrs of fresh water (via the hot water tank!) into the bilges. So that was a fun passage.

Been there, done that and any time we leave anchor/mooring the pressure pump gets shut off.

Sounds like you have air in the HW tank. Try bleeding the lines outlet line at the tank itself. Captain Obvious will point out this may be hot water.

Is there a check valve (back flow preventer) on the water heater supply line? Give it an authoritative tap if it has one.

[Windspirit]

Have you tried draining the wh? Calcium carbonate builds up in the tank in small chunks and could be blocking an opening. If the drain valve clogs up you'll have your answer