Pressure regulator causing hammering.

[Hairy Animal]

Hi, I'm new to this forum so please excuse me if I've posted in the wrong forum or whatever. I would call myself a competent amateur plumber, having plumbed our whole (1928) house from the stop tap to the cisterns in the loft, but I know there's plenty of stuff I don't know about so am always happy to learn from others. My plumbing has generally been reasonably successful until I fitted a water softener prior to fitting a new hot water cylinder (prior to fitting solar water heating). The water softener I reckoned was necessary because we live in a very hard-water area and the old cylinder I removed demonstrated this with some 5 kg of limescale inside it.

The Calmag water softener (Calsoft Mini) requires a maximum water pressure of no more than 5 bar and I was moderately certain our mains pressure is at times greater than this so I fitted a pressure regulator just ahead of the softener. The regulator is set to 42 psi, just under 3 bar which is adequate for all the taps, toilet etc that it feeds. The plumbing adheres closely to the Calmag installation requirements (see attached diagram) with the regulator downstream of the non-return valve and close to the softener (see attached picture).

At first it was fine but after a week or two we began to get hammering in the pipes downstream of the regulator. It was very varied as to what conditions set it off but usually it seemed to be worse at night when (I presumed) fewer people in the area are using water and the incoming pressure is higher. It's better during the day but not always. At first I thought that the problem might be the water softener itself but by changing the valves to bypass it, the issue was no different. I then tried fitting an 8 litre pressure vessel (also set to 42 psi) downstream of the valve & softener (see 3rd pic.). This is maybe 3 or 4 feet away on a spur off the feed to the cisterns in the loft - it made no difference either. I've tried reducing the flow at the main stop-tap and that doesn't help and now I've run out of ideas on how to fix it. At times the hammering is really bad and has already loosened one compression joint on the valve itself. It can usually be eased by turning a tap on a bit, but not stopped completely.

Any suggestions would be most welcome please?

 

[ShaunCorbs]

I would remove the nrv before the reducing valve

 

[snowhead]

Has the pipe "mains in from stop tap" got any pipe clips supporting it?
Looks like it's pulling out of the clip next to the Reduction valve.

 

[John.g]

May help if the E.vessel pre charge pressure is checked/reduced from 42 psi to 35/37 psi.

 

[ShaunCorbs]

Also that vessel isn’t rated for mains water eg drinking water

 

[Hairy Animal]

I would remove the nrv before the reducing valve

That's an interesting suggestion. I did wonder if it might be part of the problem. I'll try it if nothing else works.
[automerge]1591817588[/automerge]

Also that vessel isn’t rated for mains water eg drinking water

You're right, it's not for potable water but it's only connected in the pipe to the cisterns for the hot water and cold bath water tap. Although softened water is supposed to be drinkable it's not recommended so our kitchen tap is the main/only source of drinking water. Thanks for your note.
[automerge]1591818080[/automerge]

Has the pipe "mains in from stop tap" got any pipe clips supporting it?
Looks like it's pulling out of the clip next to the Reduction valve.

Thanks for your note. The mains-in pipe is indeed a bit short of supports, but prior to fitting the reduction valve there wasn't any problem at all with that same unsupported pipe so I don't think that is an issue. You are right that the pipe is coming out of that clip and I will replace it in due course but the problem does seem to be after the reduction valve.
[automerge]1591818217[/automerge]

May help if the E.vessel pre charge pressure is checked/reduced from 42 psi to 35/37 psi.

Thanks, that's a relatively easy thing to try. I know it's at 42 psi because I had to pump it up to that from the 1.5 bar it was set at when bought.

 

[Hairy Animal]

That's an interesting suggestion. I did wonder if it might be part of the problem. I'll try it if nothing else works.
[automerge]1591817588[/automerge]

You're right, it's not for potable water but it's only connected in the pipe to the cisterns for the hot water and cold bath water tap. Although softened water is supposed to be drinkable it's not recommended so our kitchen tap is the main/only source of drinking water. Thanks for your note.
[automerge]1591818080[/automerge]

Thanks for your note. The mains-in pipe is indeed a bit short of supports, but prior to fitting the reduction valve there wasn't any problem at all with that same unsupported pipe so I don't think that is an issue. You are right that the pipe is coming out of that clip and I will replace it in due course but the problem does seem to be after the reduction valve.
[automerge]1591818217[/automerge]

Thanks, that's a relatively easy thing to try. I know it's at 42 psi because I had to pump it up to that from the 1.5 bar it was set at when bought.

Have only just got round to trying this and it's certainly helped quite a lot. I'm still getting some oscillation but it usually dies down where before it would keep going and often get worse. Thanks again for the suggestion.
[automerge]1592235743[/automerge]

I would remove the nrv before the reducing valve

I have now tried this and again it's helped reduce the intensity of the hammering. When it does occur, the frequency is higher and it usually fades away, though not always. Thanks very much for your suggestion.

 

[John.g]

Don't know what pre charge pressure you are set to now but no harm in reducing it to 25 psi and see if this improves matters, also it may help if the EV was installed just after the PRV & before the softener.

 

[Hairy Animal]

Don't know what pre charge pressure you are set to now but no harm in reducing it to 25 psi and see if this improves matters, also it may help if the EV was installed just after the PRV & before the softener.

I tried all sorts of different pressures but no setting seemed to be right for different flow rates as cisterns refill for instance, or as the mains pressure changes from time to time. The hammering changed to a higher frequency vibration and always seemed to start no matter what I tried.

So I've removed the PRV from the pipework adjacent to the water softener and reinstalled it just after the main house stop tap where it has no close devices apart from the stop tap itself.

So far, it seems to be working perfectly with no hint of any vibration or hammering under all sorts of flow conditions.

I've been most grateful for the help offered by all - thanks; problem solved (I hope!).