House pump not priming-brand new!

[Mac2]

Spent the last two days attempting to get a new 3/4 hp Teel jet pump to prime-going nuts! I had removed a Myers 1/3 hp house pump because it was slowly loosing pressure-it was functioning. The boat had a spare (brand new) Teel pump I installed ((115 vac). I primed, turned on and it would get up to 25 psi and then sit there and then drop to just below 20 psi. I took apart and confirmed pump was filled with water. Pump would spin and get extremely hot, but never get past 25 psi. My 12 vdc pump (backup system)!works fine-they share the same plumbing. Any ideas?

 

[Turtle Blues]

Believe the first line off the top goes to the expansion tank? Standard homeowner setup would have 2nd. tee above that for water supply outlet. This prevents air pocketing and cavitation. Can't tell from your photo where you are connecting supply outlet? Also a jet pump setup requires foot valve acting as pump inlet check valve. If you are positive that inlet supply maintains prime this should not be necessary but given the disc impeller setup of that style pump it may be preventing pressure buildup when pump starts

 

[Mac2]

Yes. Top line goes to expansion tank. Water level in tank is higher than pump so it feeds water to pump-I have to turn a ball valve to cut water off so I can work on pump. I had the check valve before the intake to pump so I removed it to see if that was the problem, but it still didn’t work. Im wondering if the pump is to powerful and causing cavitation . First line off the top goes down to a tee at expansion tank and splits to supply hose.

 

[Bmarler]

I would imagine a 3/4 hp pump would have a 1inch supply line. Don’t know if that’s the problem though. As you come up to pressure the flow cuts down considerably.

 

[Turtle Blues]

So if the pump is below tank water level removing gauge would result in flowing water, indicating that all air has been evacuated from system? If this is the case next check is water volume availability to pump inlet. It may be that the combination of inlet size reduction and the size of the pump are too far apart causing starvation. Rigging something to supply full volume to the inlet would test this.

 

[Mac2]

I think both comments above are leading me to confirm my suspicions. The inlet is 1 1/4 and outlet is 1 inch. I have it reduced to 3/4 inch to match the existing hose. About 2 feet before the inlet is a filter/strainer and just before that a uv filter. This is probably combining to starve the pump. That could explain the initial rise in pressure to 25psi (water present) and then slow drop off.

 

[Lepke]

A shallow well pump will pull thru too small of a hose. It just puts more load on the pump and takes longer to come to pressure. My current boat had a 1/2" line feeding an 1.25 inlet and was working. Changing to a larger inlet pipe reduced the time to make pressure.
I suspect some fitting or hose isn't tight and the pump is drawing air. As the pump primes and starts making pressure it becomes more efficient, increasing suction and the ability to draw air thru a leaking fitting. Loose connections often will not leak water but will allow air to pass.
Where is the pressure switch? One possibility is an air pocket before the pressure switch. When the pump is running and making some pressure, open a valve at a far end of the system and let it run to check for air in the system.

 

[Mac2]

A shallow well pump will pull thru too small of a hose. It just puts more load on the pump and takes longer to come to pressure. My current boat had a 1/2" line feeding an 1.25 inlet and was working. Changing to a larger inlet pipe reduced the time to make pressure.
I suspect some fitting or hose isn't tight and the pump is drawing air. As the pump primes and starts making pressure it becomes more efficient, increasing suction and the ability to draw air thru a leaking fitting. Loose connections often will not leak water but will allow air to pass.
Where is the pressure switch? One possibility is an air pocket before the pressure switch. When the pump is running and making some pressure, open a valve at a far end of the system and let it run to check for air in the system.

I followed that procedure several times with no luck. I have a 12 volt pump plumbed into the same system (I use it to also prime the house pump) and there is no issue with leaks or sucking air. Im convinced now its the uv filter and strainer, along with 3/4 line, before the pump that is causing a lack of flow to the pump. I ordered the original style myers pump, so I will confirm my findings.

 

[Mac2]

An update: Installed a new 1/2 hp Myers shallow well pump. I tried it without a check valve. It definitely backwashed. Installed the check valve and it came up to pressure properly but I noticed it was slowly losing pressure-the same reason I replaced the old pump. A hissing sound was coming from the front/pump portion. Closing a ball valve on the feed line to the pump, stoped the hissing sound along with losing pressure. This confirmed there was no leaks in the plumbing or pressure tank. I believe my check valve was not completely sealing. Knowing my system likes to backwash, Im thinking the brass swing gate in the check valve was the problem. Both check valves I have did the same thing. I have ordered the check valves that are spring loaded and have a rubber gasket for sealing. Hopefully this will solve the problem. Glad I didn’t throw the old pump away. I will rebuild it for a backup.