Still battling water pump issue

philh wrote:
Dealer fixed the issue with water coming in from the onboard tank. According to their report, filter was blocked. BS, the winterizing suction tube worked fine and the shut off valve is now in the system with hose clamps... so that was at least removed by the dealer.

Now, I've got water hammer so bad that something is likely to break. Found no o-ring to seal the filter to the pump, added an o-ring. Did not change the behavior.

This may be an important observation, while the water hammer is undergoing, the LED lights are flickering.

It's 150 miles one way to the dealer, and I'm more than a little frustrated.

When you say water hammer are you referring to the pump pulsation noise when it's running? Or are you referring to a hammer noise when you close the faucet and the pump stops?

If you're referring to the pump pulsations I would guess that the dealer inadvertently moved a PEX line against something. Maybe try turning on the outside shower so the pump runs but doesn't fill a holding tank. While the pump is running reach in around the pump and move the PEX lines to see if the noise changes. If you can silence or minimize the noise then use a piece of foam or Styrofoam to hold the lines in this position.