water hammer

[philipb]

Hi guys,
Went to a house last week with bad water hammer on hot and cold,fitted a prv on saturday
which stopped it,the factory setting on the prv was 3 bar.all seamed ok till today when it returned
but only on the hot.preasure still same but pipes banging on hot only.It has a combi boiler and i put the prv
on the cold main after the stop tap.any advise would be appreciated.

 

[lame plumber]

get some pipe clips out and start hammering them in

 

[philipb]

Hi I should have said that the house has not had this problem for years
then suddenly this and no plumbing work done,anything to do with the boiler?

 

[stoker122]

You could try a shock arrestor or find what is setting off the hammer.

 

[woodytheplumber]

clip all pipework (not nailclips as i once used them and after a year they had relised and the hammer came back rather than calling me they called another plumber who happend to be a mate of mine but they were slagging me off anyway ha ha we all live and learn) and put resistors on all washertaps

 

[APS]

Quarter turn taps can sometimes be a problem on mains hot as they close the supply off in a split second.

 

[philipb]

You could try a shock arrestor or find what is setting off the hammer.

Hi,would the shock arrestor go in the cold mains or somewhere in the hot supply?

 

[stoker122]

Should be fitted just after the internal stopcock.

 

[philipb]

Thanks will give it some thought,dont get why all looked ok for 4 days with prv
then back to as it was with no change in preasure.

 

[CXR100]

Toolstation > Plumbing > Valves > Mini-Rester i was told you could solve a problem like this by teeing off the main cold water pipe somewhere and in a way create a small (maby 6-10 inch) deadleg , air would supposedly trap here and act like a expansion vessel!!!???? . dont know if its true or if it works, but they did this in the old days if they had the problem when a ballvalve closed off ....... so i was told!! maby somebody here could confirm this!!! you could also add a small expansion vessel like this somwhere on the main Mini Expansion Vessels - altecnic | reflex

 

[PlumbBobBob]

creating a small dead leg will work and it is exactly like the toolstation one, just a short length of tube with a cap on

 

[philipb]

creating a small dead leg will work and it is exactly like the toolstation one, just a short length of tube with a cap on

Thanks for all the info,i thought the toolstation part was just a short length of pipe with a cap on it.
Will give it a try.

 

[CXR100]

never bought one myself but ill try it next time i get the problem!

 

[CXR100]

just a quick afterthought , i assume that the deadleg has to point upwards so air doesnot escape?????