unusual water hammer?

[Calvados]

Coincidence or not, we noticed a heavy water hammer soon after a repair was made to the water main’s junction with our house (at the end of the drive).

I don’t know if it was a subsequent increase of water pressure (though there was no noticeable change in pressure from the taps or showers) but just prior to the leak/repair we noticed an element of water hammer following the installation of a new washing machine.

To counter the minor washing machine water hammer, I fitted one of the cheapr water arrestors to the back of the machine. It didn’t work.

So we think we only have water hammer when the new washing machine is used.

Then we have the water main repair and suddenly (or at least it seemed to appear just after this event) we have ‘bad’ water hammer when various taps and showers in the house are turned on.

A small amount of hammer noise seems to occur in random places under the floor bords of the first floor but the really bad hammer occurs in the pipes immediately above the stop cock and water meter. We have an outdoor tap connected to the indoor meter and the noise OUTISDE, carried through the pipe is really loud too.

To try to fix, we asked a plumber to fit a ‘proper’ arrestor near the pipes close to the meter (see photo). The arrestor was fixed to a second pipe (pipe on the left) that previously also had a tap no it. We don’t know what purpose that tap served but the plumber thought it was pretty much redundant. The tap/valve on the right is the main stopcock.

Given the set-up and the fact that we now have a small screw-in arrestor on the back of the washing machine and a larger arrestor on the ‘second’ pipe next to the stop cock, can anyone suggest a next step? I read somewhere that I could try turning the valve to reduce flow of water coming in to the pipes and to the taps but that isn’t really solving the problem…

I know it might be because the pipes have come away from their brackets but there is no easy way to access them so I’d prefer to try other avenues first!

Many thanks in advance for your assistance

 

[Johntheo5]

Any idea what the mains (static) pressure is?, also, also the large arrestor may have a bit of info like pressure in bar stamped on its end, have a look.

 

[Madrab]

Makes me wonder what some plumbers actually do when it comes to training and experience. Hammer is relatively easy to fault find for an experienced plumber. It maybe not be as easy to correct though due to access, as you suggest. Usually it's all to do with excessive pressure & slam shut valves - 1/4 turn valves creating pressure waves back down the pipe, proper pipe support is key in that.

As suggested I'd also be checking incoming pressure, flow isn't really an issue with hammer. It may be time to install a PRV on the incoming mains with a check valve.

 

[Scally-Ho]

I assume all of your pipework is well clipped, but if not then now is the time to ensure all is well held and that includes underfloor pipework which is all too often overlooked. After that check your taps and if of the loose jumper type, pin those jumpers and that includes your main stopcock. If you are able to throttle back your W/Mc inlet to just enough to operate the Mc then this will often quell it's potential to cause hammer. If all of that fails then if you have a cold cistern in your roof space, take a look at the ball/float valve as that too can induce hammer if too much play in the piston or the float is bouncing.

 

[Calvados]

Apologies for the delay folks but I now have the photos and feedback to your questions - and thank you for your collective input thus far.

Firstly, see photos of the arrestor and my water meter which show pressures etc. I will def need your advice on what is suitable etc here.

FYI, I have turned the tap a quarter turn (to lessen flow according to the posts above) and I think that helped slightly with the hammer but its still very much there especially when washing machine is on!

Re: pipework, I have a feeling some of the pipework might be unclipped (knowing that the builders who built our extension some years ago fitted or moved those pipes close to the meter and cut corners in other areas) but I do not know for sure and it would mean ripping down sections of plasterboard walls to investigate. I'll do this if nothing else works but it is also worth remembering that the extension was completed some 5 years ago while the hammer is recent (unless the pipes have comes away from the clips over time due to the pressure?) and going back to my OP, the hammer (coincidently?) appeared after the water mains repairs.


@Scally-Ho - not sure I follow 'check your taps and if of the loose jumper type, pin those jumpers and that includes your main stopcock. If you are able to throttle back your W/Mc inlet to just enough to operate the Mc then this will often quell it's potential to cause hammer'. Are you referring to the tap on the stopcock on the taps on the sinks etc? and are you saying they need to be clipped to stop them from 'jumping'?

Also, does anyone know why we had 2 taps originally (the plumber says he will remove the arrestor and refit a tap as the former hasn't worked)?

Thanks again, Cal

 

[Calvados]

just coming back to his one - anyone able to offer expert advice following the additional info provided?

thanks, Cal

 

[Madrab]

Hammer is relatively easy to fault find for an experienced plumber. It maybe not be as easy to correct though due to access, as you suggest. Usually it's all to do with excessive pressure & slam shut valves - 1/4 turn valves creating pressure waves back down the pipe, proper pipe support is key in that.

As suggested I'd also be checking incoming pressure, flow isn't really an issue with hammer. It may be time to install a PRV on the incoming mains with a check valve.

Not sure pressure has been measured? Finding out where the hammer sounds worse will help. Identifying the outlets that’s causing it etc. turning down the stop tap normally won’t alleviate the hammer, hammer is due to pressure not flow, turning down the stop tap only reduces flow. Your plumber should have sorted this by now, if they have it then time for a new plumber IMO.

IMO putting an EV on the system is just a sticking plaster, the cause needs to be found and fixed.

The 2 taps may have been down to 2 different supplies or may have been to isolate a separate outwards supply.