Pressure leak down in fresh water system

[Russell Clifton]

My fresh water pump keeps cycling about every few minutes or so. This has gone from cycling every 30 minutes but today it is cycling every few minutes. I cannot find any leaks in the lines or fixtures, so thinking that either the pump is by passing the pressure internally or the pressure tank has gone bad. There is a rebuild kit available for the pump.

The pump is a Groco PSR 12v and the tank is also a Groco, PST2. The pump looks fairly new but I have only had the boat a few months so not sure. Looked back thru old receipts for 3 years and cannot see where one was bought. Cannot find much on line about trouble shooting these parts except for the pressure tank which says that if any water comes out of the fill valve when depressed, the tank is bad. No water is coming out. Tank charged to 30 PSI. Also, if you experience the water changing temperatures while in the shower, could be the tank. We have had this issue. Cannot find anything on trouble shooting the pump.

Any ideas would be appreciated. I am thinking about replacing the tank and ordering the pump repair kit as a back up.

 

[The Other Gary]

You need to clean the check valve on the pump on the side that goes to the water tank. Sometimes a little piece of something lodges in the valve allowing the pressure to leak back into the tank. If not then you have a slow leak somewhere in the system.
Bad valve = no fresh water in the bilge
Leak in piping = Fresh water in bilge

 

[wwestman]

For some reason mine does that on occasion. What I have found is that I turn the power off to the pump for a while, then when I power it back up it pumps for a while then turns off and goes back to normal. Don't know why but it works for me.

 

[cyfarkas]

Chased many cycling issues, often hard to find. It largely depends on how visible your bilge layout is. Ultimately though, can you notice if your bilge pump area is holding more water. If yes, there's a leak you haven't found. If no, is there a sink,fixture issue? Sneakiest one recently was in the 1/4" line running to my ice maker filter that wasn't fully winterized.

In general, if a pump fails, it will leak at the pump. If it's in the pressure switch, or sucking air, flowing water will likely blow out air burps. it's simple enough to carry a spare and test swap especially if you have swivel fittings on either side of the pump. (Pumps often come supplied with them)

Hope this helps

 

[cyfarkas]

Rus, you also mentioned your hot water heater. Did you feel around it especially the bottom for a leak?

 

[C lectric]

I don't have your system or anywhere near it but I stopped relying on the built in check valves. I purchased a good quality brass check valve and installed that right after the pump in the output hose. Stopped my bleed down and quick cycle problems.
Of course I have had to deal with leaks and they can be a real pain to find but find them you must. If you are satisfied that is done then consider a separate check valve.

If the pump does need a rebuild then do it of course but consider the separate check valve.

Short cycling should not be the pressure tank.

If you drain/depressurize the system and then use a pressure guage on the P. tank air fill valve and it still shows 30PSI or whatever it is supposed to be at , then the tank is fine. If it's a bit low then use a bicycle pump to touch it up but the tank is still fine. If bladder air pressure does drop, and it will over several years, it can cause goofy operation, but not usually the short cycle as you describe.

Check the pump turn on pressure setting. If the air bladder and the pump control turn on setting are too close that can cause oscillation/ short cycling.
The bladder pressure must be lower than the pump control turn on setting bey 4-5 psi minimum.

I will add though if the bladder pressure is really low it may be allowing the bladder to be completely collapsed partly defeating the tanks intention.

Hope this makes some sense.

 

[Russell Clifton]

UPDATE: Nothing needed to be rebuilt but a part needed replacing.

On these water systems, there are two check valves. One is located right after the air pressure tank and has a pressure switch located in it that turn's on the pump when the pressure drops in the system. The other is located at the outlet of the water pump and prevents the pressurized water from leaking back into the pump. I could not even tell it was a check valve until I looked at a schematic of the pump. The one at the pump was slowly allowing the water past and lowering the system pressure.

There was no external water leak. I found it using a stethoscope and listening to the various components and could hear the leak inside the valve. Found one at Fisheries Supply in Seattle for $21.00. Thank goodness it wasn't a pump as they are over $3000.00 for that model.

Thanks to everyone for your help.

 

[Lou_tribal]

Rus, you also mentioned your hot water heater. Did you feel around it especially the bottom for a leak?

That's exactly what happened to me. Pump was cycling every 10 minutes for few second, I spent days to check everywhere until I finally find a very small leak under the water heater tank. Leak was not visible as it was going under the tank and into the bilge. Now I need tom fix this, one more thing on the spring repair list

 

[cyfarkas]

Rus, good for you! Nice diagnosis. $3000!!! Yikes, and Here i am scroogeing over $150 pumps....

 

[Xsbank]

Just an aside - a Groco air tank will cost you $200 but you can get the exact same thing without the Groco label at an irrigation shop for about $25.