DIY Doctor UK DIY Forums

Hi,
I changed out my Myson 3 port valve for a Tower 3 way valve last Summer and it worked trouble free. Now that the colder weather is here and the sytem is switching between hot water and/or heating I am getting a bang or hammer. I have had my head stuck in the airing cupboard for long enough to be able to confirm that the bang only ocurs when the valve moves to the hot water only position from either mid or heating only. It does it every time but never did it on my old Myson valve, the geared quadrant on the valve moves smoothly so I don't think it's a duff valve. A neighbour with an identical house with identical system has also fitted a Tower valve and his bangs as well!
If I can get the time right I can use it as a morning wake up device!!
Any scientific root causes would be gratefully received!
thanks in anticipation
Mike

This is good old fashioned water hammer. When the valve moves across to shut off the heating supply, the flow of water suddenly shuts the valve and the water flowing in the circuit is stopped dead causing the bang.

My guess is, from what you have said, is that this make of valve is prone to to this problem. Try turning the speed of your pump down to reduce the speed of water flowing. This of course may cause some rads not to get so hot but as you seem to have a good flow maybe there won't be a problem.

thanks for your reply,
My pump is already on number 1!
I had a suspicion it may have been momentarily dead ending but thought the discharge pressure would have slipped back across the impellor, obviously not. Are there any hardware solutions before I go for another make of valve? ( small bore spillback line to pump suction?, just thinkin out aloud ) !
thanks again, Mike

I sorted the banging valve problem!
The Tower mid position valve that was banging, only banged when closing on it's spring return default position of hot water only.
The shop swopped it for a Honeywell and I noticed that the valve stem on the Honeywell had resistance to turn by hand whereas my banging Tower valve was really free. I summised that the Tower valve was banging on it's seat, this turned out to be right as the Honeywell is silent.
Interestingly the valve architecture of the Honeywell is identical to the Tower, even the actuator head is identical, since found out that they all come from the same factory, so the Tower batch must have had a QA issue.
My old Myson valve could never have done this as it was a plug valve, the Tower / Honeywell is a ball on an ecentric shaft and therefore swings, this is what allowed it to bang/bounce shut.
No more early morning wake up calls!