water hammer with central heating


Postby greg555 » Thu May 29, 2008 11:47 am

Hi,

When my thermostat reaches temp Is it common to hear water hammer? Should this be silenced or buffered in any way? The noise seems to come from above my celling. (where the valve must be) and can be clearly heard shutting 3-4 times a night.

Could this also cause damage?
Is it common to hear water hammer from your heating system?

any replies would be appretiated !!

cheers!,
greg.
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Postby greg555 » Mon Jun 02, 2008 9:48 pm

Can anyone help with this?

Cheers,
G.
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Postby plumbbob » Tue Jun 03, 2008 7:49 pm

If you need help on a subject, it is essential to include as much information with your post as possible to ensure a useful reply.

You say thermostat. But which stat? Tank stat? Room stat? Boiler stat? Is your system gravity fed? Pumped? With motorised valves? Two port or three port? Do you have a boiler? Is it a combi or system? Does it happen when the water goes off or the heat goes off?

Look at this post.

http://www.diydoctor.org.uk/forums/view ... hp?t=11504

SO if you want a reply give some information please!
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Postby adamjoner » Tue Jun 03, 2008 8:51 pm

hi,
when u say the water hammer starts when the thermostat reaches temp, do u mean your room stat or individual radiator thermostat?
do u have a system boiler with a cylinder in airing cupboard or a combi boiler


adam
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Postby greg555 » Wed Jun 04, 2008 8:14 pm

Hi,

Plumbob..

I cant answer all the suggested parts to your reply, It really is just a general question. for the ones I can answer.. Its the thermostat that controls the room and hot water on/off. (It can also be programmed to come on at a certain time etc).. It is a pumped system (it has a a pressure gauge set at 1 - 1.5). i'm not sure about the motorised valves but I believe these shut off when the room temp is reached and think it may be this thats causing the bang?
If it is should this be heard? is it common to put it right above the living area? should they be buffered in any way or are they supposed to shut abruptly like this?

Does it happen when the water goes off or the heat goes off? - yes, when temp reached on stat (mentioned above) and the LED turned off.
Do you have a boiler? Is it a combi or system? yes, I think it is a combi.

I hope this gives you enough to help?

Thanks for the reply! it really is appretiated!
---------------------------------------------------------------------------------------------------------------------------------
adamjoner,

thanks too for replying

I think all is explained now?

cheers!
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Postby plumbbob » Thu Jun 05, 2008 9:54 pm

Right, now we have a little to work on, we can make a few suggestions.
I think there have been two or three other threads started this week asking the same question so I guess you can say this is a fairly common problem.

Water hammer is caused by the closing of a valve and the flow is stemmed abruptly. Depending on the circumstances, the noise made can be quite gentle or very loud.

Obviously though, this can put extra stress on pipework and joints and has been known to cause damage. However, this is considered very unlikely, and is really more a nuisance than anything else.

As to why this can happen on one system and not another is less clear, and can, unfortunately, be difficult to rectify particularly with a combi boiler as they contain less user adjustable parts.
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