Water Hammer revisited! Really getting me down.

[Ihavethebestdogs]

Hi, hoping to once again draw on the expertise of @pigletjohn re water hammer. And, if anyone has been there, fixed the issue and can offer any pointers, I'd appreciate it.
If you see this @pigletjohn... You may remember giving me some advice regarding a water hammer problem that is affecting almost all of the fixtures in the house (will link the previous thread at the end). Unfortunately, two more plumbers, who basically scratched their head and a few hundred pounds down, we still have the problem. I wonder if I could once again ask for your advice and insights if I give you some more information?

We recently had a water meter installed (it's outside and was installed by the water company) after we discovered the previous one was damaged and hadn't even been connected since who knows when. We had hoped this might resolve the water hammer issue as we had read online that this was the case for some previously blighted with the dreaded water hammer. However, nothing changed. Before fitting the outside water meter the water company did send some one out to measure the water pressure which was 3.5 bar, apparently very good and unlikely to cause water hammer. They also isolated everything they could (some isolation valves were not accessible) and checked those fixtures were not the cause...

We don't know if the water pressure has changed since the new water meter was installed outside so we'd need to check that with a view to possibly putting a pressure reducing valve on the incoming mains...

We had a plumber come out who was all over the house trying to locate exactly where the water hammer sound was loudest and likely coming from, to no avail. His parting words were that he could open the wall up in the downstairs utility room and possibly beyond to the upper floor if necessary to check for pipes that aren't clipped but said it would be invasive, expensive and not guaranteed to work. He suggested living with it. I asked if one faulty valve or washer could cause water hammer across almost the whole house basically and he said no, it would only clunk of the tap or toilet that needed a new washer or valve if that was the case? Is that right, pigletjohn?

I feel the noise is concentrated in the pipe running up into the Worcester combi boiler and through it, possibly up into the ceiling and beyond but the boiler was recently serviced with no issues found and the gas engineer fitted an arrestor on the boiler pipe to help protect it, though it's not helped the noise at all. I don't even know if boilers can be the source of water hammer The noise is happening on opening and closing every single tap, all toilets after flushing and refilling and the washing machine. You hear it loudly in the living room on the other side of the utility room wall. We can open and close taps slowly but that doesn't sort the washing machine or loos, and is less than ideal. Oddly, the dishwasher (a Beko which the previous owners left) runs without any hammer noise to be heard.

This same guy mentioned above swapped the washing machine and dishwasher around (put the dishwasher into the utility room and put the washing machine into the kitchen at my suggestion) to see if this helped at all since the dishwasher is always silent. It seems to have ever so slightly eased the clunking when the washing machine runs (perhaps because it is now geographically further away from where the clunk seems to be located int he utility room)...Interestingly, the dishwasher, which is now right where the clunk seems to be located in the utility room, still runs perfectly with no hammer noise. It is seemingly the one thing that we can use without feeling anxious about what is potentially happening to the pipes wherever it's placed.

Oddly, there seems to be a clunk you can feel with your fingers like a pulsation (to a lesser degree) in the main bathroom upstairs (in the pipes behind the sink pedestal) when the washing machine runs. It is a little better since the washing machine was relocated and now doesn't seems to do it on the toilet after refilling (in the same room) to the same extent.
The aforementioned hot pipe behind the sink pedestal in the the main upstairs bathroom also seems to pulse when hot water runs through it, and after you turn off the hot tap off on that sink or the bath next to it you get a bit of clunking, ticking and dripping noise (sounds like it's coming from the bath) , and then after that stops lots of small clunks and creaks for absolutely ages which can be heard in the bedroom next door. Any hot tap used in the house also causes the ticking and dripping noise in the main bathroom above which is heard in the living room ceiling below. We actually thought the prolonged creaking noises in the bedroom were from the roof or guttering until we made the connection with running the hot taps in the aforementioned main bathroom. Every sink gurgles but drains fine.

We had a glimmer of hope last week when we had to have the ancient shower replaced after its second leak. The plumbers that did that told us they may have fixed the water hammer issue because during the replacement of the old shower they found it had been installed with the valve the wrong way around and hot and cold feeds mixed up. Indeed, my husband turned on the taps, flushed the loos and nothing but blissful silence... Until, that is, I decided to turn on the heating ten minutes after they left just to check everything was in order and make sure the radiators would still come on without issue. As soon as I did that the hammer came back full force on everything apart from the dishwasher, so back to square one.

My husband thinks the problem is the downstairs loo (next door to the utility room) as a night or two ago the mini part of the dual flush got stuck down and until we worked that out and released it there was an awful hammer thud reverberating throughout the whole house every five minutes or so, much worse than the usual bang. I said I thought that it was just because the flush mechanism was stuck and it was constantly running, refilling and shutting off... The plumber before last also said there is no chance that one faulty toilet valve was causing the issue as the hammer would be limited to that fixture only, not happening on everything nearly..

The ensuite loo has started hissing after refilling so we've stopped using that. I'm getting very anxious when flushing the loos, running a tap and using the washing machine. We really want to move and I'm worried if we come to sell and have to declare the hammer issue it'll really put off potential buyers. I know it'd put me off! I don't know if all these problems can be water hammer or if we're dealing with several issues!

@pigletjohn, can you shed any light please?
A) Especially on why the dishwasher is spared and operates normally with no hammer?
B) Why the noise went away after the shower was fitted but came back with a vengeance as soon as I fired up the heating (even though the heating doesn't trigger the hammer...)?
C) Whether outdoor water meters have their own pressure regulator as I'm wondering if it's worth trying a new stop tap under the sink or getting a pressure regulating valve fitted on the hot and cold water feeds under the sink (which would mean cuttings cobs out of the board at the back of the cupboard where the indoor stop tap is located) and, lastly,
D) Whether it's worth draining and re-filling the system in case air chambers are waterlogged? If yes, can you direct us to a site you'd recommend showing how to do this? There are a few guides online but they seem to differ a bit from each other. Some say to also drain the washing machine and dishwasher too...but we have no idea how to do this... Would this be straightforward to a plumber?

I'm sorry this is so long but we wanted to give you as detailed an update as possible in the hope that you might be able to point us in the right direction. We just haven't got the money to keep throwing at the problem with no end to the problem in sight.

Previous post if it helps:
www.mumsnet.com/talk/property/5067198-is-pigletjohn-still-around-can-you-please-help-me-with-a-water-hammer-problem-thanks

Thanks so much @pigletjohn.

Definitely not pigletjohn but that's a house like this and the plumber tried EVERYTHING. As he'd agreed to fix it for a set price after doing a survey pre purchace. It was solved by replacing the tap? Old owner had botched the direction of installation on virtually everything. So there were probably other contributing factors but that was it. So it could well be a single item.

@Pieandchips999 Thanks so much for your input. Was this your house? If so, you've had no issues since replacing a tap? Can I ask how it was traced to the tap or was everything replaced in a process of elimination until the tap was hit on as the culprit? I really appreciate your help. It would be amazing to cure it by replacing a tap or a valve on a loo. Really don't fancy the wall being opened up as no guarantee it's an unclipped pipe (plus, we just don't have that kind of money)!

@Pieandchips999 Sorry, also meant to ask if the hammer was happening on everything (or, almost everything) in the house? Thanks so much!

The hammer was EVERYWHERE and so LOUD. Plumber tried a bunch of stuff first but nothing made an obvious difference. Then the tap did it. It was my first house I ever owned so crazy stressful. I only owned it about a couple of years. But the problem with fixed in a few weeks and never returned.

I can't think what else to check.I should think you've tried all the suspects. I'd look for a (very) old stopcock somewhere, if it is an old house. Probably underneath where the sink or scullery used to be when the house was built. They are often jammed or boxed in and forgotten. I think there is a loose pipe or a worn out fitting somewhere..

Apart from that you could get a pressure reducing valve fitted, just one, at the point where the incoming water pipe comes up through the floor and you (should) have your main stopcock. I prefer the ones with a pressure gauge so you can look at them. You do not need a separate one for the hot water, because if the incoming supply is capped at (say) 1.5bar, none of the pipes will be at higher pressure. 1 bar is 10 metres of head, which is enough for a 3 story house but 1.5bar should run a good shower on the top floor. Have you got an expansion vessel for your boiler or hot water cylinder? If the boiler one fails, the radiator pressure in the boiler will go up and down dramatically when it gets hot and cold, though it should not cause hammer. The cylinder (if you have one) might have a white vessel.

Pressure reducing valves are often 15mm, but if your incoming pipe is bigger, you will need a bigger size. The valve and the primary stopcock should be as big as the incoming pipe (larger ones are more expensive which is why some people fit ones that are too small). If you are happy with the plumber who did your investigation, he could presumably do it for you.

What colour and size is your incoming watermain?

p.s.
I don't see any point in draining the pipes or appliances

the dishwasher might have got an electric equilibrium valve, which opens or shuts itself gradually using the water pressure. Equilibrium valves are usually very quiet, and I like them in WC cisterns in particular, which can be annoying if you flush them during the night. The Torbeck valve is very good, but prone to sediment or grit blockages if your pipes are old, rusty or dirty. It is quite easy to dismantle and wash out if you know how (but not otherwise).

If only you could track down the faulty section of pipe, you could have it cut out and replaced, perhaps with plastic pipe which AFAIK is not prone to hammer.

@Pieandchips999 Thanks so much. Ours is every tap when switched on or off, every toilet when flushed and the washing machine. No idea why the dishwasher is spared but am thankful for small mercies! I really appreciate you taking the time to respond and give share your experience. Hoping it's something as simple as a tap! Thanks again!

You don't get pressure reducing valves on external water meters.
How is the water coming through at the kitchen cold tap? Is it spluttering ? Milky in colour? If it is it could be air on the incoming water supply pipe.

To get rid of air in the supply pipe first turn the kitchen cold tap on. Leave it on. Having left it on turn the internal stop tap on and off about half a dozen times. Any air should get pulled through. Then turn off the kitchen cold tap until you need to use it. Eventually it should clear throughout the rest of the house.

@PigletJohn Thanks for replying. It's not an old house, quite the contrary. It's less than 20 years old. Not sure if it would qualify as a new build but I have heard of others in newer houses having issues with plumbing. Many complaints online that modern residential plumbing is dire compared to that in houses built in 70s and before.

I think the stopcock under the sink is the only one (apart from the main one outside).

I know the pressure was 3.5 bar before they put in the water meter outside but don't know if it's changed since. It's perhaps worth putting in a prv as you suggest if it still measures 3.5 bar, especially if 1.5 bar would still supply decent pressure. I thought I read somewhere that water meters have a pressure regulator on them already though... If you still think it's worth putting one on (esp if the pressure still measures high) I assume it couldn't hurt? Thanks for the heads-up about making sure the prv is matched to the pipe size if we go ahead.
When my husband is home i'll ask him as I don't know what colour and size the incoming water main is...

You asked if we have an expansion vessel for the boiler. Is that an arrestor? If so, yes, but it's made no difference to the noise. Not sure about the hot water cylinder you mentioned? We have no separate hot water cylinder unless there is one in the combi boiler?
We did have an arrestor on the washing machine. That plumber added pipe and the arrestor rested on the floor.. It made no difference so we asked him to take it off.

Thanks for the info about the dishwasher. That would make sense. I wonder why all appliances aren't fitted with these equilibrium valves!

I'm hoping, as with Pieandchips999's experience, it might be as simple as replacing a tap or two, or maybe replacing valves on the loos. If we try that route - especially if the prv is a no go or doesn't remedy the hammer problem - would you be able to recommend a valve for the loos that acts more slowly or taps that will be less prone to hammer? We can't open the walls, though we might be tempted to save and open the wall if we knew it was definitely that / the exact location etc. Thanks, @PigletJohn... Will talk to my husband when I can and get back to you...

@MrsMoastyToasty

Thanks! So, if you don't get a prv on outside water meters as part of the set-up, maybe it's worth fitting one!
The kitchen tap is a mixer type. The water looks okay. That tap has been a hammer culprit along with everything else (apart form the dishwasher) but the plumber three back had me open and close it suddenly many times to trigger the hammer noise when he was trying to assess the situation. Since then it's not spluttered but it has sporadically made a kind of sudden 'chhh' noise when turning it on, especially when turning it on more quickly (I usually do very slowly to try to minimise the noise and it helps somewhat but it's not always easy to control...).
Is it still worth doing what you suggest? If it is, do I put the cold on full or just a medium flow? After opening and closing the stop tap, should I open it fully or not quite fully (as it is now)?
Thanks so much for your advice. Mumsnetters are so lovely and helpful!

It's worth a go @Ihavethebestdogs . It's what we used to advise when I worked in the water industry.

@MrsMoastyToasty Thanks! We'll try it. We've nothing to lose and it seems fairly straightforward. Will LYK how it goes.

If your water pressure is 3.5 bar then you can absolutely turn that down with a prv and it may well solve your issues. Can’t imagine the professional plumbers you had wouldn’t have thought of that though? I have a prv on my three story house and set around the 1.5 bar level. Top shower actually more powerful than the middle level one for some reason but both are perfectly useable - think the top shower has a more direct feed than the middle. Anyway. I’d defintely get a prv in the system, like you say pretty easy job to do, and then turn the pressure right down. If this eliminates the knocking then slowly turn up pressure to a point where hopefully still quiet but everything is useable.

@NonmagicMike
Thanks for the info. One of the plumbers did suggest it but he had one foot out of the door and said he wasn't sure it'd solve the problem, and he'd have to cut into the area surrounding the stop tap and it'd look unsightly. That wouldn't bother me in the least if it solved the water hammer! I'd consider it a small price to pay! As you say it can't hurt and it's reassuring to know your fixtures are doing okay on 1.5 bar (weird that the top floor shower is more powerful than the middle level one but would make sense if the top shower has a more direct feed, I suppose).
One thing I'll add....Our next door neighbour (semi-detached) has a separate supply and they don't get any water hammer at all. You'd imagine it'd be a problem for them too as the pressure must be the same into their home! They hear nothing; from their side or ours! Weirdly, I sometimes hear a clunk when they turn on the tap in their utility room (backs onto utility room although, unlike them, we have no sink in ours). I asked about it and she invited me in and demonstrated on her taps (off, on a couple of times and no issue at all!)
Thanks for the advice. Will try a few things suggested here and if they don't work will get a prv on the main supply... As you say, not too complicated or costly so definitely worth a shot!

We did similar to what MrsMoasty has suggested and it helped a little, however what actually fixed ours was the stopcock in the road (that only the waterboard fiddle with) being turned on properly. Apparently one of the workers had only turned it 3/4 back on after doing work on the road pipes (flushing??). No idea why it caused the hammer but turning that all the way off then fully back on sorted the problem. Our actual pressure had been unaffected all that time so I suppose 3/4 instead of full should have been okay.

If you want non-hammering fill valves in your WC cisterns, get Torbecks. Buy one spare of each type just in case you get rust or grit in them, you can swap them (plastic nut) and wash out the clogged one at your leisure on the kitchen worktop where you have plenty of light and space (the parts are very small), not crouching over a cistern with wet hands. When you try you will find it very simple and you don't even need a spanner. I have known it happen, but in my own house they last around 20 years.

If you want non-hammering taps, get the old-fashioned types with a knob or capstan that rotates. Not ceramic taps with a quarter turn, and definitely not ceramic mixers with a joystick. Have a look at the Bristan range, or phone their customer service and say what you're after.

But I would go for the pressure reducer first. WC valves are cheap, but a set of bathroom taps might not be. Do any that you think need changing.

A 20 year old probably has bright blue plastic supply pipe. Likely 20mm or 25mm o.d. Might be 32mm which is better in some circumstances. Avoid abrupt reductions in diameter.

@Pixiedust1234 Thanks for the info. The outside stop tap has been opened and closed multiple times since this problem started but it's certainly worth making sure it's fully open - (in case it never has been fully opened and and that's causing hammer like it did for you) - to see if it makes any difference.

@PigletJohn Thanks for the heads-up about Torbecks. I'm thinking if the hammer can't be fixed that having less dramatic valves will help. Would they work on loos with a button flush? Like the one in the first pic in this flush?
https://www.hvpmag.co.uk/Toilet-manufacturers-called-on-to-rethink-dual-flush-buttons/12841
Thanks for the heads-up re buying spares.

Thanks too @PigletJohn re the taps. Oddly, the taps in the small loo downstairs - which backs on to the utility room where the hammer seems to be concentrated (actually sounds like it's in the boiler!) - has the more traditional rotating-type taps and they are big offenders when it comes to the water hammer we're experiencing. I have to turn them on and off super gently. You actually hear a boom as they turn on and a big clunk as they turn off if you don't open and close them really slowly. But, I can see why this type would be recommended over quarter turns taps or ceramic mixers with a joystick as they are really hard to control, especially when turning off. I'll make a note of the Bristan brand, thank you.

Re the supply pipe. You can barely see it where it connects to the internal stop tap as the cut-out around the stop tap is small but I can just about make out a bright blue pipe, like a thick(ish) hose. Couldn't say what diameter it is as I have no idea how I'd measure it, but it looks like it's on the wide side, maybe the width of a standard garden hose pipe or a little thicker. @PigletJohn Re what you said about avoiding abrupt reductions in diameter? Can I just ask what you mean by that so I can make sure whichever plumber we approach does what we want wrt fitting a prv and does it properly?

@PigletJohn Apologies for so many questions but may I ask what you make of the noises heard through the living room ceiling below the main bathroom, for example when we run/ just after we run the hot tap in the downstairs loo? I'm wondering how using a downstairs hot tap could cause noises in the above bathroom that then transmit through the downstairs living room ceiling. It's quite disconcerting. It sounds like ticking and bop-bop-bopping or dripping. My husband said it's likely pipe expansion as there is no such noise to be heard when cold water is run! But, I'm concerned it could be a hidden leak (sounds like it comes from inside the bath which some bright spark totally tiled in!) In the same bathroom, when running the hot tap at the sink, there is clunking and a kind of pulse in the pipe as the water flows through it.
I probably sound paranoid but when my husband first bought the house he inherited a leaking shower, concealed so he didn't know until till the ceiling was badly damaged. A friend actually stuck a screwdriver into the ceiling and water gushed out. It was in the light fitting globes too... A real nightmare so I have a fear now of hidden pipes, especially when they make noises that don't feel right.

I'm just wondering if we're dealing with one or two separate problems, or this is all caused by the water hammer and fixing that (if we can!) might resolve the second problem I just mentioned.

Apologies for taking up so much of your time @PigletJohn.
Thanks again for sharing your knowledge - I really appreciate it!

That's too long.

A Torbeck is a fill valve. It is independent of the flush valve. It is particularly small so unlikely to get in the way. You can get a bottom-entry or a side-entry version, depending where the supply pipe enters your cistern.

Measure the height of your old valve stem if bottom entry.

Valves with a brass connector are preferable to all-plastic because they are less likely to suffer cross-threading damage.

Any plumbers or builders merchant should have them, but possibly not the full range.

Example:

https://www.screwfix.com/p/torbeck-bottom-entry-fill-valve-1-2-/8120t

Thanks @PigletJohn. Will make sure when we call the plumber that I tell him this! Thanks you!