Bad case of water hammer.

[Mike01]

Hi everyone
I have been a plumber for 3 years now, I haven't come across many issues with water hammer so I'm not to sure what to do.
it happens on the hot pipework, more specifically the hot taps in the bathroom (basin and bath). but it only seems to happen when I open the hot tap to a certain point, any less or more and it wont happen...
another issue which I'm sure is related, is when the bathroom hot taps are running, the kitchen tap will start to run, even though its firmly turned off. another thing worth noting here is the kitchen tap works fine and does not cause the water hammer.

The system is a combi boiler, a shock arrestor is fitted on the cold feed to the boiler, also the hot feed from the boiler has a teddington combisave on, I have never came across these before so not sure if this is related.

i have checked all the pipework i can see and only found one instance of pipework touching, but I held them apart and tried again and the issue still persisted.

the pipes are vibrating so bad it has caused two leaks so far that I had to repair today. hoping to get this sorted before more leaks happen.

thanks in advanced for any replies!!

video water hammerimage of boiler

 

[Chuck]

Are the pipes clipped properly and at the right intervals? The fact that some are touching but you can "I h[o]ld them apart" makes me suspicious.

There have been many discussions of water hammer on this forum. Use the 'search box' on the top right of this page to find them.

 

[snowhead]

Having just read up on the Combisave, I'd suspect that firstly, either faulty or just being there.
It would seem that at a particular flow rate it could be causing sudden pressure fluctuations.

Is it in a position where it can be temporarily removed and bypassed?

Also, expect the unexpected, don't rule out the hammer caused by ball / fill valves on the mains cold side.

CombiSave - Thermostatic Restrictor Valve | Teddington

An Award-Winning British Innovation That Reduces The Amount Of Water And Gas Used In The Initial Heating Process, The Combisave Thermostatic Restrictor Valve Can Be Fitted To Almost Any Combination Boiler To Save You Money And Time.

teddingtonsystems.co.uk

 

[Mike01]

Are the pipes clipped properly and at the right intervals? The fact that some are touching but you can "I h[o]ld them apart" makes me suspicious.

There have been many discussions of water hammer on this forum. Use the 'search box' on the top right of this page to find them.

Yes all the pipes that I can see seem to be far apart, except under the bath where the hot going to the tap touches the cold, they are both firmly fixed in place but I managed to hold the pipes apart, I also slotted some cardboard between them to try and rule this out. When I go back I will look into it further, maybe disconnect that section of pipe.
Thank you for your reply.

 

[Mike01]

Having just read up on the Combisave, I'd suspect that firstly, either faulty or just being there.
It would seem that at a particular flow rate it could be causing sudden pressure fluctuations.

Is it in a position where it can be temporarily removed and bypassed?

Also, expect the unexpected, don't rule out the hammer caused by ball / fill valves on the mains cold side.

Yes it can definitely be bypassed. I will try this when I go back next week.

Cheers!

 

[Phil]

Is the kitchen tap ceramic disc? The cartridge on the cold side is probably worn, if there is an isolator on the tap turn it off and see if the hammering stops.

 

[Mike01]

Is the kitchen tap ceramic disc? The cartridge on the cold side is probably worn, if there is an isolator on the tap turn it off and see if the hammering stops.

Yes the kitchen is ceramic disc. I’ll definitely try that! I’m guessing it’s a bit of a process of elimination to try and find the cause.

 

[Mike01]

hi everyone, quick update incase anyone comes across this page with the same problem.
the issue was the kitchen tap, the ceramic disc cartridge's were worn and loose, the tap was so old the customers just wanted a new tap, once i changed it the problem was solved!