So you called out an engineer for water hammer.
Boiler working however pipes making this noise
he changes PCB and charges you for it and you pay?
Get him back to put in your old PCB and refund you then install a shock absorber on your Main Cold Feed.
Has your area had water meters fitted recently?
maincold feed ok
no work carried out on system prior to this
engineer will sort pcb refund[/quote]
What im getting at is that where i live alot of people were getting water hammer due to new water meters being fitted.
The non return valves in the meter had failed and not only were they getting hammer but there Combis were firing up from the cold tap.
Shock absorbers cured this problem and thats why i asked.