water hammer prevention

[plumber89]

hi there just replaced old bath taps and basin taps for cermaic discs ones, but as these ones are 1/4 turn on and off you can turn them off quickly, if you turn the cold off quickly then it creates a bad knocking noise, have checked all pipework and nothing seems loose ( everything lagged and clipped)
the water hammer can be prevented if i turn the isolaters down,
these basin and bath taps are running off a cold main, which is fed to the bathroom from the loft
could i put a flow restrictor in to prevent this
any other suggestions would be great cheers

 

[diamondgas]

Have you heard of a "shock arrestor"? Small expansion vessel fitted to the mains to offer a 'cushion' of air so there's not such a sharp stop as taps are turned off.🙂

 

[plumber89]

oh k , ill have a look for them, was thinking of fitting a prv in the loft to the main just before it enter bathroom,the noise in the water hammer is just coming from inside the pipe then? its not actually the pipes banging against anything then? as i can see pretty much the whole main pipe as the floor is up and it isnt banging against anything and is clipped and lagged

 

[plumber89]

by the way, is a shock arrestor that small ball looking thing?
if i was to connect this to the main above the bathroom. is there certain regs i have to do for example does it have to be a certain height etc?

 

[plumber89]

http://www.****************/shop/Plumbing/Valves/Potable%20Water%20Shock%20Arrestor/d20/sd2696/p93058 would this be suitable, and does it need to be fitted before appliances

 

[diamondgas]

there's probably some bofffin's more up on the causes of hammer here 'plumber89'. Something to do with back pressure in valves or something? I might just google it! lol

 

[diamondgas]

by the way, is a shock arrestor that small ball looking thing?
if i was to connect this to the main above the bathroom. is there certain regs i have to do for example does it have to be a certain height etc?

Yep you've got it .. it's about the size of a tennis ball. It can be fitted anywhere on the mains suply after the stopcock!

 

[plumber89]

oh k cheers m8 just read up, aparently its best to be fitted as close to the appliance that is making the noise as possible, as it will only stop the noise when the back flow has reached it, so i may just fit a prv up in the loft as this will do all applicance, but its definatly worth knowing about them , thanks again.

 

[diamondgas]

oh k cheers m8 just read up, aparently its best to be fitted as close to the appliance that is making the noise as possible, as it will only stop the noise when the back flow has reached it, so i may just fit a prv up in the loft as this will do all applicance, but its definatly worth knowing about them , thanks again.

Thanks for the info regards it being fitted close to the appliance as possible.. I wasn't aware of that 🙂 The first lot of combi boilers produced came with them integral, I remember!

Good luck sorting out the problem!

 

[plumber89]

ye i just read up that the noise will only be stopped by the time the backflow reaches the shock arrestor, so its advised there fitted as close as possible, i will try a prv tomorow, and if not will try a shock arrestor.

must there be a pipe banging against somewhere to create water hammer then? or can it just the noise inside the pipe

 

[REDSAW]

sonic shock waves.
sound like the wife snoring!

straight long pipe run mostly affected as it looses 'snort' around bends.

 

[diamondgas]

It has something to do with the speed in which the pressure returns to standing .... something like that! lol

Just googled "shock arrestor" and noticed it had something to do with pipe vibration being the reason why it's best fitted as close as possible to the offending article! 🙂

Regards hammer ... It can be the tap washer jumping as it closes sending a vibe down the pipe. the noise could be at the tap .. Honestly don't know! 🙂

 

[diamondgas]

sonic shock waves.
sound like the wife snoring!

straight long pipe run mostly affected as it looses 'snort' around bends.

Can't beat a straight long run ... 🙂 Can certainly interrupt the snoring for a while :rofl:

 

[Dave (chris)]

My understanding of it is that the pressure wave inside the pipe makes the noise, but can also cause the pipes to move and bump into other pipes or boards.

 

[navylark]

I had this problem also. Went to my local plumbers merchants (I am DIYer) and I picked up a Pressure reducing valve that I fitted straight after the internal mains stopcock. The device is similar to an accumulator that we use on hydraulic systems in aircraft. The device looks like a small tap with a grey plastic shroud and limits the dynamic pressure to 3 bar, mine was well over 4 which caused the banging. I hope this helps from an amateur, it also doesnt look like a tennis balll and has cured the banging I was experiencing on a number of appliances.

Can take a photo and send it if required, I think it only cost £10-15 probably a lot less with an account.

Cheers Nick

 

[leelister6]

Try turning the stopcock down a bit, that costs nowt and works 9 times out of 10!

 

[navylark]

Lee

I did try that first because of the obvious cost saving, but as I discovered that will only limit the rate of supply not the pressure and the hammering was still there.

Nick