Hi, we have a Grundfos 15SQE07 3/4 hp constant pressure pump in our 265ft well producing 15gpm. Pump is set 240ft deep. System is set at 70psi and small pressure tank is set at 49psi. System works pretty well but on the pressure gauge when water is being used the psi starts out constant at 70psi and then drops down to 60psi and then moves up to 80psi and then settles back at 70 for a few minutes and then the cycle continues. You can also hear the increased water being pushed through pipe when it pushes up to 80psi. It almost seems like pump is slowing down and then speeds up even though water usage has remained the same. We also have irrigation installed connected with T at pump and the pressure variation is seen in the sprinkler heads. Our well company has replaced the tranducer but nothing changed. Any ideas what could be going on? Thanks.