Megaflo - water hammer

[ChrisR]

Customer reports what sounds like water hammer in the HW pipe.
One of those situations where the users become less certain of their facts when questioned hard, but they're saying:

Noise occurs first thing in morning (6am), they think it's when the CH/HW come on, and not at other times of day at all. Noise stops as HW is drawn off, sometimes returning as tap is turned off after a few litres.
Noise definitely starts before anyone draws water.
Also saying that a dripping hw tap can be connected with it - if they turn the tap off hard the noise stops.

No water in tundish/ discharge pipes. Have had him recharge the air gap anyway, though it made no difference.
This is not a high mains pressure area.
Installation is about 2 years old.

Does anyone have exp of the pressure reducing (or non return) valve doing this?

(Brain still addled from 3 weeks of string bikinis and cocktails. Unless it was the cr*p plumbing and diarrhoea)

 

[gazthepottertonengineer]

could it be down to poorly routed pipes i.e not clipped

i had better get learning about these things if the rumours are true

 

[noonespecial]

Could it be expansion / contraction noises rather than water hammer?

 

[Agile]

String bikinis in Tunisie ??

Certainly NOT in Libya !!!

As far as noise is concerned I would suspect pressure reducing valves or pressure release valves.

Just an idea from lateral thinking, suppose the pressure went up overnight to say 6 Bar and the reducing valve was letting by and the tank pressure went up as well.

Come 6 am when the labourers get up mains goes down to say 2 Bar then perhaps there is a chattering as reducing valve lets by backwards?

Test to leave a tap fed by tank leaking by a little.

If this cures it then take apart and clean the pressure reducing valve.

Tony Glazier

 

[croydoncorgi]

There's supposed to be a non-return valve in line before you get to the pressure control part....... Check valves don't often chatter.

 

[Agile]

The non return valve is usualy in the same housing as the pressure reducing element and I had grouped the two parts together as one.

This is a problem not "often" encountered otherwise Chris would not need to ask!

Thats what makes it all the more interesting to get to the root cause.

Tony

 

[noonespecial]

String bikinis in Tunisie ??

Certainly NOT in Libya !!!

As far as noise is concerned I would suspect pressure reducing valves or pressure release valves.

Just an idea from lateral thinking, suppose the pressure went up overnight to say 6 Bar and the reducing valve was letting by and the tank pressure went up as well.

Come 6 am when the labourers get up mains goes down to say 2 Bar then perhaps there is a chattering as reducing valve lets by backwards?

Test to leave a tap fed by tank leaking by a little.

If this cures it then take apart and clean the pressure reducing valve.

Tony Glazier

Yes and could close the isolating valve on the feed to the cylinder to check whether the problem is being caused from external pressure fluctuations.

Try leaving cylinder heating on and then off overnight to see if that has any effect on problem.

 

[Agile]

"""Yes and could close the isolating valve on the feed to the cylinder to check whether the problem is being caused from external pressure fluctuations. """

That would also be fine but ONLY if there is no cold feed taken after the pressure reducing valve. In that case there may be toilet flushing to disturb the test.

Tony

 

[ChrisR]

Thanks all.
No CW takeoff, I think, because the mains pressure has always been pretty low, around 2 bar. It may well be only at 6am that the pressure goes high enough to make the p red valve do anything at all. I believe the area is reservoir-fed and they're on top of a hill, and Thames W have reduced the pressures recently so would be surprsed if it goes up a lot.

Have had dcv's chatter/sing at low flows, but from the verbalisations down the phone line it sounds too low a frequency.

Money's on the prv but...

--

More likely to find string bikinis twixt goolies and gallows in Libya I think.
They have some big plumbing (6m diameter pipe) but no bathrooms where anything much works.
But if you (locals, even) step off the curb, the traffic stops for you to cross, how nice.