Pipes laid directly on joists

[Gillespie]

Hi.

We bought a 1960s house in Nottingham last year and it suffers from really noisy pipework - creaking, clanking, banging as well as some whooshing sounds. I managed to pull up a piece of floorboard on the first floor yesterday and the pipe that I can see is sitting in a notch in the joist. The joist is about 18cm/7" deep and the notches are roughly 2cm deep. Is it okay to make the notches wider and deeper where necessary to stop the pipes coming into contact with them? And then what would be the best padding material to use to try and reduce the noise? I was thinking about getting some Talon Snappit Pipe Covers that I could trim down and slide over the pipes.

If I had the time I'd like to do this myself but, if not, who would be the best tradesperson to try and get in? A plumber, carpenter or somebody else? Or is this one of those types of jobs that nobody really wants to do?

Any advice would be much appreciated!

 

[paulc]

The size & depth of notches is dictated by the distance from the end of the joists - There are tables on the internet that give recommended maximum depths & widths.
For my pipes, I've wrapped some 3mm thick dense foam round them. Seems to work quite well as I don't hear any noise from them. A bit of stout canvas or denim may well work too.

 

[a twig]

I’ve used these under floorboards to reduce clanking pipes - easy to install and do the job.

10x Rubber Lined Steel Strong P Clip Clips Hose Pipe Clamps Cable Wire (16mm) https://amzn.eu/d/0gMZaz4

Where they didn’t fit I cut down pipe insulation and packed that in between the pipe and the timber

 

[Gillespie]

Thanks @paulc and @a twig, those look like good options.

Based on the details I found here, I don't think making the notches any deeper is going to be possible, as the maximum notch depth suggested for a 175mm depth joist is 21.9mm:

Notches & holes in solid timber joists

I'm planning on replacing any nails that I remove when I pull up the floorboards (20mm deep). The suggestions I've read elsewhere are to use 4mm head screws that are 40mm long.

 

[CliffordPope]

Clanging pipes can also be caused by water hammer - air bubbles trapped in sections of pipe that run slightly uphill so the bubbles never quite get either flushed out nor can simply rise to the surface, or else by awkwardly aligned pipework with a lot of right-angled bends.

 

[Toby Newell]

1. Do not deepen notched joists. No notching is good, pipes should be redirected and / or fed through middle of joist.

2. Ideally pipes should be fixed using plastic or rubber lined metal clips. Do not use bare steel next to copper, any condensed moisture can cause galvanic corrosion and a pinhole leak.

3. Water hammer is not caused by air in the system, actually the opposite. Air in the system causes spluttering at taps. Water hammer is caused by the water slamming into the ends of the pipes via inertia when a valve (or tap = manual valve) shuts off.

To combat this plumbers build in 'air springs' (water at normal pressures is virtually incompressible whereas air is very compressible) look for pipes (normally two of them) normally running vertically at the end of a run, often behind sinks or in boiler cupboards, these terminate in a cap. There should be a few tens of cm of air in there which acts like a shock absorber. You need a plumber to come and sort that.

4. Yes the job is incredibly minor, the plumber will do it when he comes to sort the water hammer.

5. I use 3.5mm x45 to 55mm (I now use 3.5x55mm Spax Wirox) T10 lost head screws. I was an early adopter when Tight Fix introduced them, years before you could buy them in the shops. I have probably used over 100,000 of them, they have similar if not better holding power than a 50mm cut floor nail.

 

[CliffordPope]

3. Water hammer is not caused by air in the system, actually the opposite. Air in the system causes spluttering at taps. Water hammer is caused by the water slamming into the ends of the pipes via inertia when a valve (or tap = manual valve) shuts off.

To combat this plumbers build in 'air springs' (water at normal pressures is virtually incompressible whereas air is very compressible) look for pipes (normally two of them) normally running vertically at the end of a run, often behind sinks or in boiler cupboards, these terminate in a cap. There should be a few tens of cm of air in there which acts like a shock absorber. You need a plumber to come and sort that.

Well, I never new that. Thanks.
I'd just assumed it must be air in pockets that couldn't get out. It only happens with our system just after there's been a water shortage and someone has run the tank dry. It takes a few days to flush itself out and clear all the air out, and then it stops hammering.

 

[Toby Newell]

Well, I never new that. Thanks.
I'd just assumed it must be air in pockets that couldn't get out. It only happens with our system just after there's been a water shortage and someone has run the tank dry. It takes a few days to flush itself out and clear all the air out, and then it stops hammering.

I only found out a few years ago myself. I think the air pocket gets filled with water and reduces the 'shock absorbing' effect. You can sometimes solve the issue by turning the water off, draining the system by opening the highest taps, then the lowest taps, then refilling, this sometimes recharges the air cushion.


I think in your case the opposite is happening, the air chambers are getting filled with water then air is slowly accumulating afterwards. They sell them specially now, I think they are called arrestors, they are just proprietary small sections of closed pipe, traditionally plumbers just put copper caps onto small runs of normal pipe, every house should have them.

 

[a twig]

Well, I never new that. Thanks.
I'd just assumed it must be air in pockets that couldn't get out. It only happens with our system just after there's been a water shortage and someone has run the tank dry. It takes a few days to flush itself out and clear all the air out, and then it stops hammering.

In your case it is possible that you just have a system which had been modified so much over the years there are height changes in which air gets trapped in “not by design”

In our old place our heating used to be very noisy, when we went over to a combi with the system running at higher flow rates and pressures, after a week of running the noises went away, which would imply that it was driving out the “non-designed” air which solved the problem

 

[Toby Newell]

In your case it is possible that you just have a system which had been modified so much over the years there are height changes in which air gets trapped in “not by design”

In our old place our heating used to be very noisy, when we went over to a combi with the system running at higher flow rates and pressures, after a week of running the noises went away, which would imply that it was driving out the “non-designed” air which solved the problem

Your plumber probably fitted a shock arrestor, thats why the problem went away. No such thing as 'non designed air' lol, air is compressible, any air in the system will absorb kinetic energy and turn it into heat, air does not cause water hammer, its literally what it says, the inertia of the water is hitting the end of the pipes, like, er, a hammer...

 

[a twig]

The plumber was me, so no he didn’t not all tapping and banging noises are water hammer. If it had been, and the arrestor had been fitted it wouldn’t have taken a week for the noises to stop…

 

[Feltwell]

Where they go across the joists, a bit of traditional felt pipe lagging passed round them works wonders and needs very little room. Same when pipes have had to come up through floorboards for radiators - slightly oversize hole, bit of felt lagging stuffed round the pipe, pipe can move without any noise being created. Felt lagging can still be bought from proper plumber's merchants very cheaply.

 

[Toby Newell]

The plumber was me, so no he didn’t not all tapping and banging noises are water hammer. If it had been, and the arrestor had been fitted it wouldn’t have taken a week for the noises to stop…

true, some are thermal movement or coupled to the pump seeing as noise travels 6x better through solids but 'water hammer' also results in pipe movement that creates pings as well as bangs... you may get a lump or tack hammer sound...