Clunk Noise from Hot Water Tank Cupboard

[tek_architect]

Hi Everyone,

I'm looking for some advice as to what the loud clunking noise is that occurs when the cold water feed is activated in my house - either from a tap, toilet, washing machine, dishwasher etc.

The symptoms seem to occur if the cold water has not been accessed for an hour or so. An example would be, first thing in the morning, turn on the cold tap (even just a trickle) and there's a bit of a surge in water flow and then a clunk noise from the hot water tank cupboard. The water flow then reverts to a more normal flow. This occurs if you turn any cold tap on a tiny bit or full. This occurs if you flush the loo, when the dishwasher fills or if the washing machine fills.

We have an unvented Santon hot water system. I believe it's a Premier type tank, about 250 litres. The tank also has an expansion vessel. I think the noise is coming from the gubbins below plinth where the tank sits. There's all sorts of pipework, valves etc hidden in there. It's a newish build house - the system has been in for about 4 years.

I don't think it's water hammer as it doesn't happen when you switch the tap off or for example when the dishwasher stops filling.

I've tried things like turning all the cold taps on in the house - thinking it might be some kind of airlock. You can all laugh if you want!

The incoming mains feed to the house has a grey Caleffi pressure reducing valve with replaceable filter. It says 3 Bar on it. There is a + and - on it that appears adjustable with a philips screwdriver.

I just want to know whether the source of the problem could be either from the incoming mains or if it lies in something wrong in the hot water tank cupboard. Looking to either fix myself or know what I'm talking about when I call out a professional.

Any help would be really appreciated.

Regards

David

 

[happyflyer]

The washer in the stop tap can act like a hydraulic ram pump, once it starts moving, sometimes it just doesn't know when to stop, in other words it has no brain, it needs a little help, a long time ago we would take them out and hammer up the shaft until you had to bang them back into the hole, this would then make them useless as a NRV, did they ever perform such a duty, one will never know.

Tony

http://www.youtube.com/watch?v=u2nGlnMNXrw

BTW water hammer on the ram pump is much slower than that caused by household plumbing fitting

 

[tek_architect]

keefy,

I am like you I would go to that first, they are a pest sometimes, but this only started 6 months back, still it might be, still lots of bits and pieces that might trigger it, sometimes cracking the stop tap down will cure it if it the jumper in the stop tap, lessens the gap between the seat and the washer.

Hay well all sent to try us Keefy, nice to have brains , I have never used mine, " now have I " I can't remember now!!!:38:

I turned the stop tap clockwise a couple of turns as it was fully open. That was last night. Thought it had made a difference but got a clunk this morning unfortunately.

Cheers

 

[tek_architect]

My thought would be why do you have a PRV (yes, the Caleffi device) on the incoming mains? Is the water pressure in your area particularly high? According to the manufacturer's blurb the factory setting is 3 Bar. According to the Santon instructions the PRV on the HW cylinder is set at 3.5Bar, so with the mains pressure lower than that it isn't doing a lot and the check valve built into it would be giving you the clunk when the water tries to flow backwards!
An easy suggestion would be to adjust the pressure off the Caleffi unit until it is above the setting for the HW cylinder, so about 4 Bar. Is there a gauge on the PRV? What model is it?

To be honest I'm not sure if the water pressure is particularly high in the area. We've had the house from new for 4 years so this was attached inline to the stop valve under the utility room sink. It doesn't have a guage. There's no model number I can see on it but it looks like model 5334 based on what I can see on the caleffi site. If I increased the pressure in the house could that not put the pipe work at risk? Is there anyway to adjust the pressure of the santon? Or is that too dangerous for someone unqualified and not feasible because it has to run at 3.5 bar?

the 5334 details on the site says you can attach a pressure guage but I can't fathom out how.

cheers