Hot water pipes clanging when hot water turned on/off

UnsureAboutthis

Hello as above.

We have lived here for over ten years.

The problem started about two years ago.

The worst culprit is the bath hot water tap makes a very loud clan when first turned on. We try to mitigate the clang by slowy turning it on - the sound lasts for around 5 seconds.

The basin makes a noise hot tap turns on but only about 10% of the noise, the washing machine is the same and every time it takes hot water

The sink, nearest to the boiler makes the least amount of noise

I've turned the under sink stop !!!!!! off and drained system of water in taps first on the ground floor and then sink, but did not touch the bath or the w/c's.  The noise was slightly reduced for an hour or so.

Can you help?

FreeBear

Sounds like you could do with a hammer arrestor - https://www.screwfix.com/c/heating-plumbing/hammer-arresters/cat10420003

grumbler

Water hammer normally happens when water is turned OFF, not ON, and doesn't last for few seconds. An arrestor might help, but the reason remains a mystery.

FreeBear

grumbler said:

Water hammer normally happens when water is turned OFF, not ON, and doesn't last for few seconds. An arrestor might help, but the reason remains a mystery.

My bad. Misread the opening post..

Perhaps it is linked to a high water pressure or flow rate, in which case a flow regulator/restrictor might be the answer.

vacheron

You mentioned hot taps.

If it isn't water hammer, it could be the hot water causing the pipes to expand and shear againt a beam or something while the pipes warm up.

Do you also hear anything after use as the pipes cool down?  

ThisIsWeird

UnsureAboutthis said:

Hello as above.

We have lived here for over ten years.

The problem started about two years ago.

The worst culprit is the bath hot water tap makes a very loud clan when first turned on. We try to mitigate the clang by slowy turning it on - the sound lasts for around 5 seconds.

The basin makes a noise hot tap turns on but only about 10% of the noise, the washing machine is the same and every time it takes hot water

The sink, nearest to the boiler makes the least amount of noise

I've turned the under sink stop !!!!!! off and drained system of water in taps first on the ground floor and then sink, but did not touch the bath or the w/c's.  The noise was slightly reduced for an hour or so.

Can you help?

Hi UAT.
What type of boiler and hot water system do you have? Is it 'combi', where the boiler delivers instant hot water on demand? Or do you have a hot cylinder? If the latter, is it mains/invented, or do you have a cold water tank in t'loft?

UnsureAboutthis

Thanks all

I did not think an "arrestor" would work as we've done nothing to the water

Yes, it is the hot water outlets only and really bad when turning on bath hot tap as per my OP

It's a combi boiler, Valiant Eco 831 I think it is.

We did have the water ejected by the water man from near our outside main stop !!!!!! near the water meter as there was a bbuest main on the main road about 100 metres from us - cant recall if it started happening then or a few months before that

The "hammer" is most prounounced with bath taps and the level tap on it is a bit loose since I changed the washer in the hot tap and freewheels to open but you need to use a bit of force on the lever to stop but it does not drip

400ixl

Have you checked the header tank in the loft for the float valve? We had similar a few years ago and the float in the header tank was bouncing due to the valve being worn.

UnsureAboutthis

Just noted the basin hot tap makes slightly more of a noise, a hammer noise as you turn the tap off more so than turn on - it sounds as though its coming from under the bath near th taps but we've not had pipes touched - the CH was put in soon after we moved in, inc all pipes, we had the house totally refurbished  inc electrics part from upstairs and all was good until recent months, year we cant recall getting this noise

The stop !!!!!! on the pavement I am assuming there is one near the water meter, if i turned that down a bit would it make a difference?

UnsureAboutthis

400ixl said:

Have you checked the header tank in the loft for the float valve? We had similar a few years ago and the float in the header tank was bouncing due to the valve being worn.

We always have them taken out so we can drink water from the taps upstairs and no risk of freezing/flooding. Thank you for trying, I appreciate it very much.

ThisIsWeird

When you turn on your cold tap in the kitchen, do you become wet all down your front? Ah-ha, I thought so.
Your mains pressure (and flow) is too high.
A PRV fitted just after your stopcock ( the one in your house) is a better solution that partially turning down 'cocks.
The above is only a guess, of course, and you'd need to measure your pandf. But good chance it's above 3 bar.