Water Hammer

[stillbill]

Newby to the forum
Just had new GCH system installed in my bungalow - much warmer now. BUT have noticed new water hammer double slam every time the boiler shuts off the cold or taps are turned off sharply - I am told high pressure may be the cause - odd since there was no WH previosly. I have checked the water rate (roughly) at 15- 17 litres a minute and read up on water hammer arrestors (£30 ish from Plub Center etc ) -
2 Qs : 1. are they any good and 2. where best to site the beast?
many thanks for reading

 

[jtsplumbing]

If you have a new Wocester boiler they advise fitting a Shock arrestor if you have high water pressure also good idea to fit a pressure reduceing valve, some of the plastic parts in new boilers dont like it, have a look in installation book it will tell you , you need to call back your installer.

 

[stillbill]

Hi thanks
I have contacted them previously and am in contact later this week - need ammuntion
The boiler is Dimplex combi 30 . the installation manual (online) does not mention water hammer only this

3. When the domestic water system includes any device whichprevents water expanding back towards the supply (checkvalve, loose jumpered stopcock, water meter, water treatmentdevice) then an expansion vessel must be fitted (e.g. Zilmet160ml, R​

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1/2 15bar).A single check valve must be fitted as shown in Fig. 10 toprevent backflow to the supply pipe and to ensure the efficientoperation of the expansion vessel which is required toaccommodate the thermal expansion of the water.If the hot water expansion is not provided for, then highpressures can develop which may result in damage to fittings​

and devices on the system.

not relevant i expect

 

[jtsplumbing]

They are on about an expansion tank what you want is a schock arrestor about the size of a tennis ball fits just under boiler on cold water pipe (Mains) into boiler, did they not leave you the installation book / benchmark (log book) witch must be filled in on compleation of installation.

 

[mountainman]

You've stated your water flow rate, do you know the water pressure?

 

[stevetheplumber]

is this an electric boiler ?

 

[stillbill]

Yes I have the paper installation book same as online versn. All paper work was completed and registered. I am still looking for technical infor supporting the need to protect the boiler - to show installers.

 

[stillbill]

The dimplex gas boiler has all relevant paper work and is registered. I need technical info to support the need to protect the boiler from water hammer using an inline arrester near the boiler - to persuade the installer to add one.

 

[Marcus Poate]

I like this tropics. For that, I have learned a lot from this post. I am glad now.