CH HW Pipe Hammer Problem

[wires]

System: Gravity Fed, Tower Mid Valve on CH/HW, pump below, modern system.
Problem: When Tower mid valve moves over to HW it appears to 'overshoot' slightly and then move back and settles. When it 'overshoots' there is a loud pipe hammer banging. Water in header tank is warm. I was going to change the Tower valve but cannot convince myself it is actually the problem?
Previous plumber has submerged vent pipe under water in header tank to prevent air being sucked into system - is this right?
Cheers.

 

[dal5band]

It's definately not right to submerge the vent pipe - the one that goes a couple of feet above the tanks and down - you may well get a circuit of hot water set up.

I think that's the way these valves work - the motor overshoots and trips a microswitch then it settles down to the required position. Try securing the pipes if there any loose ones and reducing the pump speed by one notch to stop the water hammer.

 

[wires]

It's definately not right to submerge the vent pipe - the one that goes a couple of feet above the tanks and down - you may well get a circuit of hot water set up.

I think that's the way these valves work - the motor overshoots and trips a microswitch then it settles down to the required position. Try securing the pipes if there any loose ones and reducing the pump speed by one notch to stop the water hammer.

Thanks for the reply. I have already turned the pump speed down to II from III but to no avail. All pipework appears well clipped.