Water Pump Running

[NWSailor]

Hello. I recently installed a brand new Jabsco Accumulator tank (1L) into my water system because the old one was leaking.

It worked great for a week or two. Then, the pump started running periodically while the faucets are closed. It will pump for a second or two every 5-10 minutes or so.

I checked all hose connections and haven't found any leaks. I tried adding more air to the accumulator tank and the pump continues to run periodically. I emptied all the air out of the accumulator tank and this has given me the best result; the pump will still turn on periodically but less often and usually just one pump at a time.

-It seems if the bladder is fully deflated is the accumulator tank doing anything?
-Is this an issue that happens if the accumulator tank is not pressurized properly?
-I read the accumulator tank should be lower psi than the pump, is there a way I can measure the psi created by the pump? I am using a tire gauge to check the psi of the tank.
-Any other trouble-shooting ideas?

Thanks!

 

[Rick D]

I had a similar issue after changing out a water pump. Turned out to be a water heater connection which cracked. I had checked everything else, and realized I had not checked that.

 

[jssailem]

Basic understanding of the accumulator.
When your pump runs, it pressurizes the water in your system. Your accumulator has air/water separated by a membrane. When water pump runs it compresses the water in the system. At the same time the water compresses the air in the accumulator. Since air and water compress at different rates, the Air acts as a pressure reserve that maintains the water pressure as you pull water from the system. Eventually the air/water pressure is equal in the accumulator. When the water pressure gets below the sensor in the pump the pump turns on.

If your pump runs constantly you have a leak somewhere. Perhaps the valves on your fixtures are dripping water into the sinks, the toilet or the shower drain. Perhaps somewhere in the system you have a hose or hose fitting that is leaking.

Last possibility is that the pressure sensor in the pump is faulty. I think that is the least likely.

 

[jeepbluetj]

Or the valves inside the pump are allowing the pressurized water back into the unpressurized side.

 

[dlochner]

On top of the accumulator tank there should be a Schraeder valve, same as on your car tires and bicycle tires. Use an ordinary low pressure tire gauge to measure the pressure.

You still have a leak. Some can be hard to find because the leak is very slow and the source of the leak is buried behind something else. I've spent the past 6 months looking for one.

 

[NWSailor]

Yeah, I have checked all the connections. Is there a reason the amount of air in the accumulator tank bladder affects how often the pump runs?

 

[jssailem]

Is there a reason the amount of air in the accumulator tank bladder affects how often the pump runs?

Simple answer is yes. The accumulator is supposed to reduce the pump running. No air in the accumulator means just the water in the system is compressed. If air is in the accumulator, then the air is compressed greater that the water and it allows the water to run longer than just the water compressed in the system. The air decompresses as the water is released from the system. At the point the air and water are at the same pressure it is like the accumulator is not there. Then when the water pressure is lower than that set in the pump the pump starts.

The way you phrased your observations was confusing to me.

 

[dlochner]

Yeah, I have checked all the connections. Is there a reason the amount of air in the accumulator tank bladder affects how often the pump runs?

Only if the volume of the water in the tank drops sufficiently. It is possible that the accumulator has a leak, but unlikely. You have a leak somewhere, could be a dripping faucet, could be a bad connection.

Look for evidence in the bilge areas. See if you can locate where water is running down into the bilge. How often does your bilge pump run?

Put paper towels under all the fittings, any drips will be easier to see.

A good candidate for a leak is on the outlet side of the hot water tank. The pressure on the outlet side will be higher than the pressure on the cold water side. Turn off the HW tank to see if things improve.

 

[dmax]

Basic understanding of the accumulator.
When your pump runs, it pressurizes the water in your system. Your accumulator has air/water separated by a membrane. When water pump runs it compresses the water in the system. At the same time the water compresses the air in the accumulator. Since air and water compress at different rates, the Air acts as a pressure reserve that maintains the water pressure as you pull water from the system. Eventually the air/water pressure is equal in the accumulator. When the water pressure gets below the sensor in the pump the pump turns on.

If your pump runs constantly you have a leak somewhere. Perhaps the valves on your fixtures are dripping water into the sinks, the toilet or the shower drain. Perhaps somewhere in the system you have a hose or hose fitting that is leaking.

Last possibility is that the pressure sensor in the pump is faulty. I think that is the least likely.

At the risk of being pedantic, water, like most liquids, doesn't compress The water pressure compresses the gas in the accumulator.

 

[dlochner]

At the risk of being pedantic, water, like most liquids, doesn't compress The water pressure compresses the gas in the accumulator.

And water when heated will expand, which is why the leak is more likely on the HW side of the system, a connection that is fine at normal water pressure may fail when the water is heated and the pressure increases from expansion.

Another potential source for the leak is the HW tank. The may develop a leak on the bottom which not immediately visible. The pressure relief valve on the tank is also suspect. There should be a hose leading to the bilge somewhere, a small leak will not be visible.

 

[Sailgunner]

I had a small leak just before the pump. It is almost impossible to find. I tighten the fittings and that did the trick.

 

[jviss]

Dry things with a towel and then probe with tissue paper - toilet paper or facial tissues.

Yes, small leaks are hard to find. With my new-to-me boat on which I have re-done much of the plumbing with what I think is the best boat plumbing connector system - Parker O-ring/Grab-ring Tube Fittings - I have eliminated leaks. I had some initially, but they were easy to find, and easy to fix. It was a process there was a kluge of brass, nylon, silicone sealant, and so on. Now it's all Parker except for transitions to brass pipe fittings for connections to ball valves, expansion tank, etc. I installed a pressure gauge in the head so I can check on and debug pump and other plumbing issues, and I can see that the system holds water pressure with the electrical power off for an entire week when I'm away.

 

[jviss]

Think of the accumulator tank as a spring. The air inside, which is highly compressible, acts like a spring. The virtually incompressible water pumps into the accumulator, compressing that spring, until the pressure pushing back from the spring through the water reaches the high pressure cut-off of the pump's pressure switch. Then, as you use water, the volume of water in the accumulator diminishes, pushed down by the expanding air, until the low set point of the pressure switch is reached, at which point the pump comes on to pump the air pressure back up. So, the pressure you are monitoring, and the switch is acting according to, is air pressure, like a remote pressure gauge linked to the air by incompressible water.

 

[BlowMeAway]

Check the air valve (Schraeder) for air bubbles seeping out using some soapy water. If leaking some air, tighten the valve stem inside the valve.

 

[Johnb]

Go back to post #4. That was the cause for me.