Noise after running hot water

[maltaron]

System is sealed fully pumped powered by Stanley Brandon oil fired cooker/boiler. Airing cupboard with cylinder and valves etc separated from head end of bath by stud partition. Pump seems OK. After running a bath the header tank in the loft finishes filling after about 2 minutes, then a loud throbbing noise (like a single cylinder diesel on tick over) starts from the airing cupboard and continues for about five minutes then fades out. There is no loss of pressure in the system. Any ideas will be appreciated. Thanks

 

[gigz]

Could be a washer/ball valve problem. You'll have to get up into the loft and lift the ball valve manually to check.

 

[Armo74]

Have you checked the ball valve in the CWSC?

 

[maltaron]

Thanks for the replies. I have checked the ball valve and it appears to be fine, water flows in at mains pressure when the valve is opened. The problem began on Wednesday evening for no apparent reason i.e no noticeable change in the system.

 

[gigz]

Did you stay up there when the noise happens ? It could let the water through ok but if the washers perishing it will make a terrible noise vibrating throughout the house, sometimes stopping when the tanks full.

 

[jeff the gasman]

Does the noise stop if you open a cold tap at the kitchen sink CWM?
If so it's definitely the ball valve in the cold water tank.
Jeff

 

[JohnD]

look in the CWC. The hammer may coincide with the ripples bouncing across the tank and making the float lift and fall. A new or rewashered valve will almost certainly cure it, but also use pipe clips to clamp the pipes firmly to wall or roof timbers to prevent it vibrating.

 

[maltaron]

Many thanks for the helpful replies. I think that it is not the ball valve as the noise does not start until after the tank is refilled and the ball valve closed. However. I will re washer the valve and check by opening sink tap later.

 

[JohnD]

the noise I am thinking of occurs when the tank is just at the "completely full" stage so only a tiny ripple is needed to move the valve between open and shut, and back again.