Fresh water system pump cycling on and off?

Air O'Nautical

Air O'Nautical

Well-Known Member
Feb 5, 2008
2,316
Port Saint Lucie Florida
Boat Info
1995 400EC. Raymarine E80, Tridata, 4kw dome, Garmin 943
Engines
2013 7.4L Mercruiser Blue water.
Hurth straight shaft 630's,
Westerbeke 7.0 BCG
My fresh water pump is cycling on every 10-15 min. for about 2 seconds.
I have crawled all over and cant find a any leaks in the system.
I dont think i'm loosing any water from the tank.

Is there a check valve in the pump itself....there must be right?

Thanks,
Mark.
 
Check the filter at the water pump. It is usually a clear plastic piece that comes apart for cleaning. If clogged it can cavitate and induce air that eventually bleeds thru and causes the pump to cycle; or there could be a hairline crack in it inducing air and cycling the pump.
 
I think there is a pressure sensor on the pump itself that you can adjust.
 
jpk33 said:
Check the filter at the water pump. It is usually a clear plastic piece that comes apart for cleaning. If clogged it can cavitate and induce air that eventually bleeds thru and causes the pump to cycle; or there could be a hairline crack in it inducing air and cycling the pump.
Click to expand...

Ive replaced my filter twice, and each time I swear I'm going to replumb my bilge so its in a more tucked away spot. In my bilge its mounted on the vertical side of where the lower bilge steps up to the raised side areas on each side. You can't help but lay or step on it when you are trying to do any engine work on the port side. Of course I haven't yet .... :\
 
My pump was cycling and I found the stern shower hose was not completely turned off. I never use that washdown hose so I forgot about it.
 
Thanks for all the ideas..
I just cleaned the screen and it was nasty.
Strange because, I recently cleaned it, maybe last month.

It just cycled again so, maybe a new pump is in order.

I did bleach the system because of a funky smell and I bet the pumps internal check valve (if there is one) got damaged from the bleach treatment.
At least the water isnt funky anymore.
:)
 
Do you have an icemaker? If you do, the hose fitting under the icemaker can leak due to the washer shrinking over several winters. On an EC that leak will be under the icemaker box inside a cabinet and will run to the nearest hatch gutter which is under your port seat base. There is enough gutter and drain hose that the leak is probably evaporating before it exits the boat. 3-4 drops a minute will cause the water pump to cycle about as frequently as you have indicated.

If you don't have an icemaker.............never mind.
 
Take a small piece of toilet paper and gently wipe each and every connection/fitting and look to see if the paper is wet which will indicate a leak.
 
The diaphragm style freshwater pumps do indeed utilize check valves. (two, to be exact). If they are worn, or fouled with a slight amount of debris, or a biofilm, then they will allow a very small flow of water back to the fresh water tank.

To diagnose, run the pump for a minute, with a faucet open, to purge any air trapped within the pump. Then, find the discharge line from the pump, trace it to its first connection, break that connection, and install a cap or plug. You now have removed the possibility that a leak is somewhere else in the pressurized side of the system.

Turn on the pump. It should immediately shut off, when the pressure builds. If it cycles, you know the check valves are allowing water flow back to the tank, and you have found the problem. If the pump no longer cycles, you have a leak in the pressurized side of the system, and you'll have to find it.

Dale
 
Thanks Frank,

I forgot to check where the ice maker used to be.
Swaped out to a refrigerator 5 years ago.
Dont remember if the ice water line was capped of removed..
I will check for my leak there.

Seasalt....Good idea.

Dale, thats what I will do this morning.
The minor problem is driving me crazy!
If I need to replace the pump which brand would you use?

Thanks,
Mark.
 
Last edited:
MasterFab said:
The diaphragm style freshwater pumps do indeed utilize check valves. (two, to be exact). If they are worn, or fouled with a slight amount of debris, or a biofilm, then they will allow a very small flow of water back to the fresh water tank.

To diagnose, run the pump for a minute, with a faucet open, to purge any air trapped within the pump. Then, find the discharge line from the pump, trace it to its first connection, break that connection, and install a cap or plug. You now have removed the possibility that a leak is somewhere else in the pressurized side of the system.

Turn on the pump. It should immediately shut off, when the pressure builds. If it cycles, you know the check valves are allowing water flow back to the tank, and you have found the problem. If the pump no longer cycles, you have a leak in the pressurized side of the system, and you'll have to find it.

Dale
Click to expand...

Yep, two check valves in the pump. Good explanation Dale. The other one in the pump is to keep dockside water pressure from filling your fresh water tank when hooked to the boat via the inlet/regulator. http://www.westmarine.com/webapp/wcs/stores/servlet/SiteSearch?Ns=Most This also has a check valve in it (facing the other direction) to hold pressure in the system when the pump is on and there is no hose connected. This was the culprit when i had the same problem as described by the O.P. It was leaking in the transom locker and went unnoticed as it was draining overboard through the small weep holes at the bottom of the locker onto the swim platform and into the bay a couple of drips at a time hence cycling the pump.
 
Jack380AC said:
Do you mean pressure release valve on the hot water tank? I'm not sure why there would be a check valve on the hot water tank. If so, where is it?
Click to expand...
I really don't know if there is a check valve or not but I could see where there might be to prevent the hot water from mixing backwards. Maybe....:huh:
 
I am having the same issue and I believe it to be the pressure release valve on the hot water tank. The pop-up is old and rusty so it is not sealing correctly. As the line leads to a through-hull, no leak is found in the bilge but the water (when the water pump is turned on) is flowing into the river. Hope to find a replacement part in the next couple of days.
 
I had the exact same issue with my pressure release valve. Only thing it didn't show up unless the water in the tank was hot. Tried to find the source of the leak while the boat was on the trailer. No leak anywhere, and the pump didn't cycle at all. Took the boat out onto the lake and ran it for a while and sure enough the pump started cycling again. It was then I noticed water going overboard. I got the replacement pressure temperature / release valve from Home depot.
 
Thanks. I'm going down friday to put everything back together after Irene and to continue the "where's the fresh water leak" saga. I'll check this out closely.
 
When hooked up to the dock water do I still need to have the fresh water pump on? I recently replaced the fresh water pump....works fine. However I don't get much water pressure when on dock water...it improves when I turn n the fresh water pump. What,if anything, am I doing wrong?
 
I had the same issue and there is a spring type valve and as the pressure builds up in the system it pulls the spring up and this shuts off the pump. Over time the spring wears out and needs to be replaced. The spring being worn out does not hold in place and leaks pressure and then the pump cycles again to build back up pressure and you get the idea.
 
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