Problem with Vaillant eco tec boiler

[alanem]

My 10 year old Vaillant Eco Tec Boiler pump/fan occasionally turns on for 10 secs when the cold water supply is turned off at the tap or toilet after use. If the tap is turned off slowly, it doesn't happen. Any suggestions please?

 

[ShaunCorbs]

Needs a non return valve and a shock arrestor fitting as the shock wave (from shutting the tap) is triggering the flow switch

 

[alanem]

Needs a non return valve and a shock arrestor fitting as the shock wave (from shutting the tap) is triggering the flow switch

Sorry but just seen your reply and thanks for it and your interest. Where should these be fitted near the boiler or incoming supply? Thanks again

 

[ShaunCorbs]

Sorry but just seen your reply and thanks for it and your interest. Where should these be fitted near the boiler or incoming supply? Thanks again

Near the boiler

 

[Last Plumber]

You possibly have a dead leg on the hot water system somewhere. Getting rid of that would more than likely stop the problem.

 

[alanem]

Thanks a lot for your help