Flojet Water Pump hammering

This is very common and usually doesn't have anything to do with air in the lines.

The pumps start vibrating when it is coming up to pressure and the pex pipe starts hitting the wooden walls.

There is a kit to add a soft hose between the pump and the rigid pex pipe will help some but I put pipe insulation everywhere the pipes were touching wood and I put a piece of thick rubber under the pump to reduce the noise.

Very quiet now.

How's your battery? I've not heard a sound like that before.

WHEN is it doing that??
Low water demand
After closing faucet
All the time faucet is open

????

Happens when one or more faucets open and never stops until faucet is turned off- regardless of demand. Battery is full and does it even with generator. A tech got it to stop one time by opening/closing the valve from the tank to the pump about 5 times in a row...he said it was priming (though this unit says it does not need priming). He didn't check the shower though and as soon as it was turned on, the hammering started again. We tried holding the pex and made sure none (at least around the pump area) was touching anything but it didn't seem to be the cause. We had a similar set up in our Airstream (different pump manu.) and it never made a sound...

My first attempt to fix is the flexible/soft hoses and following pex to add dampeners where it touches anything...

I also read there is a pressure valve screw that can be adjusted but it isn't showing on the cut-sheet for our model

Thanks for all of your replies...

How far are you opening the faucet? Does it do it with a faucet wide open? Sounds like the pump flow capacity is exceeding the rate of discharge from the faucet. That pump has a 4.5 GPM capacity and will definately short cycle when using the shower. Adding an accumulator will solve that problem.

prichardson wrote:
How far are you opening the faucet? Does it do it with a faucet wide open? Sounds like the pump flow capacity is exceeding the rate of discharge from the faucet. That pump has a 4.5 GPM capacity and will definately short cycle when using the shower. Adding an accumulator will solve that problem.

Yes, I have a 2 gallon residential expansion tank. It stops the short cycling, holds enough for a few nightly potty runs w/o the pump, and as a bonus it cut down the annoying burst of hot water when taking a Navy shower.

Adding an accumulator tank solved a similar issue for me.

PostRoadFarm wrote:
Happens when one or more faucets open and never stops until faucet is turned off- regardless of demand. Battery is full and does it even with generator. A tech got it to stop one time by opening/closing the valve from the tank to the pump about 5 times in a row...he said it was priming (though this unit says it does not need priming). He didn't check the shower though and as soon as it was turned on, the hammering started again. We tried holding the pex and made sure none (at least around the pump area) was touching anything but it didn't seem to be the cause. We had a similar set up in our Airstream (different pump manu.) and it never made a sound...

My first attempt to fix is the flexible/soft hoses and following pex to add dampeners where it touches anything...

I also read there is a pressure valve screw that can be adjusted but it isn't showing on the cut-sheet for our model

Thanks for all of your replies...

Is the water flow from faucets pulsating also?

Pressure switch...factory pre-set for 40# shutoff
No adjustment screw

Our pump does that when we switch from fresh water tank to city water hookup or vice versa and forget to change the setting for the water system.

accumulator

and a new pump fixed my issue