Conditions under which fresh water pump should run?

Atalla

Atalla

Active Member
Sep 1, 2020
244
Seattle
Boat Info
2007 38 Sundancer
Engines
Twin Merc 8.1 S Horizon V-Drives
Hello folks - Are there any mysterious conditions which would cause the water pump to run other than when a faucet is open or toilet filling? I've been hearing the pumping sound from time to time, in short bursts, maybe 2-5 seconds, when nothing's happening on the boat.

My son and I were hanging out in the marina today to watch the Steelers/Ravens game and we're just sitting around and the pump ran. Nobody touching anything. Hot water heater not on. Heater was running in the cabin but I don't think there are any connection points between fresh water and the heater. This was happening over the weekend while we were out on the boat. Woke me up a couple times in the night.

Thoughts? I've got nothing.
 
It's either a small leak or the pump itself isn't holding pressure the way it was designed. Look around for any small leaks in the engine room or faucets that may be dripping just a little. Also consider installing an accumulator tank to prevent frequent fresh water pump cycling.
 
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Yep, you have a leak either in a plumbing line, a fixture or the pump, or possibly some combination of the three. Should be pretty easy to trouble shoot and fix.
 
Mine started doing that and shortly there after failed completely. I would first exhaust the possibility that there is a leak some where. you will need to look at every coupling and valve on the boat. I would start at the transom shower. If no leaks found and you don't know how old it is I would just replace it or at least get one to have as a spare so you are not stuck some weekend with no water.
CD
 
If you turn all noise off in the boat and sit in the engine room to start and listen you may hear a drip. I have had some leaks. Feel the fittings where you can see them and under the sink. One shower feed line was leaking and the carpet was wet in the V birth. It took me a week to figure out it was the feed line behind the shower. Listen at night in bed you may hear a drip.
 
I had this happening and it ended up being the wash down spigot in the aft locker been bumped enough that it had a drip.... so simple, but took a little while to find
 
Do you have an icemaker which could account for intermittent pumping?Beyond that, the most common causes would be air in the water line or a leak.

Some years ago I spent weeks trying to find a water leak causing cycling. I isolated it to the hot water circuit but could not find it. Finally, I found that it was the pressure relief valve on the water heater, which was plumbed overboard. Replacing that valve regained my sanity.
 
The last leak I found was the shore water line. It was behind the wall and dripped to no visible area was wet
 
I have the same issue and it drives me nuts! I read somewhere to check your hot water heater pressure release valve. I looked at mine and I think its the culprit. Planning to replace in the spring. I am also curious about this accumulator tank. @Nater Potater...can you elaborate?
 
mdolesh said:
I have the same issue and it drives me nuts! I read somewhere to check your hot water heater pressure release valve. I looked at mine and I think its the culprit. Planning to replace in the spring. I am also curious about this accumulator tank. @Nater Potater...can you elaborate?
Click to expand...

An accumulator tank simply stops the fast/constant cycling of the water pump by adding a water reservoir and a bladder pressurized by compressed air. Once installed, the pump will cycle much less often when water is being used (as you are initially depleting the water from the reservoir). The larger the accumulator tank, the less frequently the pump cycles. It's better for the pump as a result.

I've installed one on every boat I've owned and can't speak of any downsides...
 
I love this forum! This is exactly what my boat needs (and maybe a new water pump). When the kids are brushing their teeth using a slow stream of water the pump sounds like a machine gun. Btw...how loud are these things supposed to be?
 
mdolesh said:
I love this forum! This is exactly what my boat needs (and maybe a new water pump). When the kids are brushing their teeth using a slow stream of water the pump sounds like a machine gun. Btw...how loud are these things supposed to be?
Click to expand...
The accumulator will drastically slow the cycling during things like brushing teeth, washing hands. I have used the smaller one (24oz) due to space constraints, but the larger ones are even better in this regard. Better yet, you can install it anywhere on the cold water side of your plumbing (under a sink, in the ER, etc). It doesn't have to be at the pump to function properly.

As for water pump noise, my experience is that even the good ones are loud. Mounting them on rubber isolation feet or similar helps but I've never seen a "silent" one. I've been told Headhunter (https://www.headhunterinc.com/product/x-caliber-12-24-dc-pressure-syste/) makes excellent units that are virtually silent...no first-hand confirmation however.
 
Last edited:
Thanks Stephen. I dont need it to be silent...I actually kind of like knowing when its running or not. It just seems louder than it should be at the moment. I think mounting it on rubber feet will be a great idea. Also going to look into this accumulator idea!
 
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