Water Hammer

[megawatt]

Hi Guys,

We've had major water hammer for some time and, as I don't really want to rip the house apart to get at all the pipework I'm considering fitting a shock arrester just after the main inlet stopcock ... something pneumatic such as ...

http://www.ashfordheating.com/images/uploaded/sealed_system_fittings.pdf

(Altecnic Shock arrestor SS Exp. Vess. Pneu. ZI-300016S/S £32.65)

Before I do, are they any good or should I start lifting floorboards

All advice would be greatly appreciated.

Thanks

 

[chrishutt]

You can get them much cheaper, but wouldn't it be better to get to the root of the problem? The water hammer will be generated by a float valve or stop valve and amplified by loose pipework. It shouldn't be too difficult to pin down the source and rewasher.

 

[megawatt]

it happens with every valve in the house, all taps and all cisterns, both showers ... The dishwasher & washing machine make pictures jump off the walls ... Knocking isn't restricted to one area either, knocking is heard all over the place.

I can minimise the effect by reducing the water flow by semi-closing the main stopcock but its not ideal as we have 2 thermostatic showers fed from the combi (Worcester Highflow 3.5) which are nice and powerful with the normal incoming pressure.

Edited: Sorry, I forgot to ask, where's best to get them from (assuming they actually work)

 

[ChrisR]

I remember one occasion where nothing I did had any effect on the water hammer I got after I'd converted a flat to a combi. The pipes were really well fixed, and it wasn't anything to do with the only float valve. But every time I turned the tap off it started, and went on for 15 seconds, almost spooky. Even cut a pipe to get any air out - no different.
Put one of these

on, and ..... it was just as loud but slowed down!
So I put an iso valve in series with it (just on a tee) and could adjust the noise nearly right out. The tap still turned off with a quiet thunk but the customer didn't notice. I saw a smaller thing in a merchant recently too, probably just as good.

 

[chrishutt]

The water hammer will be generated by a ... stop valve

Did you check the washer on the main stop valve?

 

[ChrisR]

I did on mine - even swapped the valve!

 

[chrishutt]

ChrisR, I'm not trying to teach granny to suck eggs. I meant the poster.

 

[megawatt]

Yes, the main stop valve was replaced 4 weeks ago (it took me all day to locate the main isolator in the street)

 

[chrishutt]

Maybe it's the main isolator in the street? Have you asked the water company to check this?

Try part no. 11355 here

 

[megawatt]

the one you've pointed out is a MUCH cheaper version than the thing I originally looked at

At that price I'll fit it immediately after the main stop valve and see what happens.

Thanks for all the help.

 

[Nige F]

Pressure reducing valve and shock arrestor from a PTS branch, cheap as chips and I`m on commission

 

[ChrisR]

Chris H's is the one whose pic I showed - sorry I should have showed the text too!

I believe, though I'm not sure where from, that they should go near the source of the trauma - ie the water outlet tap. Do let us know if you experiment!