well knocking

I have a 600 foot deep well running a 1 1/2 pump. There is an additional check valve at the 250 foot level. When the pump shuts off, I here a series of clunks, Two or three, each getting softer. It has done this for years. Now it is starting to bug me. I changed the check valve and the pressure switch. No dice. The pump was also changed a couple of years ago. ANY IDEAS ?

Which check valve did you change?

bob...

The One By The Tanks. Also When The Pump Was Replaced That Valve Was Changed. I Do Not Know If They Changed The One Half Way Down The Well.

I would remove the one by the tank and I think your clunk will go away.

bob...

It Is Worth A Try. It Is The Eaisest To Get At.