pressure reducing valve?

[apcdave]

Hi - called out to a property yesterday. The guy was complaining the toilet cistern was noisy filling and the valve closed with a thump. I found by closing down the main stopcock it solved the problem, The stopcock is now just about one half turn open , there is still plenty flow at the taps and the cistern fills quietly , but wondering if should recommend fitting a pressure reducing valve. Never fitted one before

thanks

dave

 

[ecowarm]

Yes sounds good to me, not too expensive either

 

[scotty plumber]

Was there an electric shower fitted? If so turning down the stop-valve that much will affect the peformance. Was there not an isolating valve at the cistern? Sound like a problem at the ballvalve

 

[ecowarm]

Was there an electric shower fitted? If so turning down the stop-valve that much will affect the peformance. Was there not an isolating valve at the cistern? Sound like a problem at the ballvalve

Scotty I have to disagree with you, why would there be a problem with the ball valve? just sounds like v. high pressure.
Also shutting down isolator on cistern will cause excessive noise if it is high pressure, Pressure reducing valve way to go imo

 

[SimonJohns]

If this problem is a new problem on an existing system. I would of thought it would of been the diaphragm

Maybe even fitted a 1212pt4 with flow restricters

 

[scotty plumber]

Scotty I have to disagree with you, why would there be a problem with the ball valve? just sounds like v. high pressure.
Also shutting down isolator on cistern will cause excessive noise if it is high pressure, Pressure reducing valve way to go imo

Most cistern ball valves should be able to cope with high pressure water, If it makes a thudding noise when shutting-off i would be pretty sure that it would be a torbeck style inletvalve there fore i would change it to brass styled one ( if possible) as they shut off more gradually which would prevent the thudding.

 

[jtsplumbing]

Getting a lot of pressure problems here in the SW, due to water board relining pipes, shower / taps / ball valves ect not likeing it also combi - boilers so best to fit PRV to serve all of house.

 

[diamondgas]

You could also considder fitting a shock arrestor, especially if fitting a prv you'll need an expansion vessel

 

[ecowarm]

Diamond an expansion vessel is not required on a cold water main?

 

[diamondgas]

Diamond an expansion vessel is not required on a cold water main?

I thought it was required if you fit a pressure reducing valve! What takes up the expansion of the cold water in the pipework of the house when the heating comes on and heats it up?

 

[kay-jay]

Im with diamond.on this. I thought you should use one but depending on pressure. 6bar and upwards iirc

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[GQuigley67]

if there is enough room in pipework for expansion i wouldnt think an EV would be neeed

 

[Megaflo-Experts]

No EV required on cold water main! The pressure reducing valve only reduces the water pressure and has nothing to do with heating up the water or it expanding!

 

[diamondgas]

No EV required on cold water main! The pressure reducing valve only reduces the water pressure and has nothing to do with heating up the water or it expanding!

See my understanding is that a pressure redcing valve will shut off the return path to the mains incoming and isolate the domestic installation .... if so what takes up heat expansion in the cold water pipework?

 

[Megaflo-Experts]

I'm not sure what the return path to the mains is?
The cold water shouldn't expand much, it's not heated.

 

[PlumbBobBob]

cold shouldn't be heated unless there is cross contamination occurring

 

[dancinplumba]

when cold water enters a property it picks up the heat in the property, this causes expansion and an increase in pressure. if prv installed, this will prevent expansion being taken up by the incoming main and you need an exp vessel

 

[SimonJohns]

All well and good saying about the main takin up expansion. There is usually a dcv/cv fitted in boundary box

 

[zzzjim]

Could this expansion be a flexi hose killer ,

( Was thinking washing machine hose will allow some )

What would Iv of pipes after prv be ? ( for a 4 deg to 22 deg average )

 

[kay-jay]

The main risk is on sections of pipe between non return valves and stop taps and pressure relief valves etc where there is high pressure and a possibility of heat expansion. Often a mini arrestor is sufficient and will protect appliances like combination boilers etc

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[kay-jay]

See my understanding is that a pressure redcing valve will shut off the return path to the mains incoming and isolate the domestic installation .... if so what takes up heat expansion in the cold water pipework?

I agree mate.

Sent from my GT-I9100 using Tapatalk 2

 

[diamondgas]

I'm not sure what the return path to the mains is?
The cold water shouldn't expand much, it's not heated.

The fact that it does expand means it will require somewhere to expand hence the need for something to take up the expansion ... It may only be a thimble full but if there's nowhere for it to expand into there's a chance it'll pop something or other! The cold water entering a property takes up the heat of the house and thus expands ... Boiler manufacturers knew about this way back when combi's first came on the market and would come with a mini arrestor fitted as standard.

 

[Nostrum]

Interesting one. Personally I think an EV would be overkill although wouldn't hurt except the extra expense. Most houses are metered these day and they all have c/v in as far as i'm aware. Never related any problems to this other than thermal effects from a combi boiler which normally specify a c/v before e/v. My understanding of this was to reduce any possibility of cross contamination of hot or partially heated water expanding back to a point where it could be drawn off via a cold tap?

Also if the cold main can take 6+ bar static then surely 3bar plus expansion wouldn't increase beyond this, although would be interested to see the sums.

 

[diamondgas]

Have you ever watched a pressure gauge on a combi when the EV has lost its charge? Rapid rise in build up of pressure within a very short period of time! Water is virtually none compressible so any expansion will raise the pressure in pipework if there's no means provided for the water to expand into.

 

[Nostrum]

Yes I know what you mean DG, but water expands at a higher rate the hotter it gets 4oc being where it is most dense.

4-21oC I make that about 0.5% increase in volume. So say as an example a house contain's 30 mtrs of 15mm cold water main x 0.145ltrs = 4.35ltrs + 0.5% (0.02175) = 4.37 ltrs

I'm stuck here for a minute, i'd like to try and equate that into a pressure rise! (as I have nothing better to do with my time at the moment)

Not saying who's right or wrong, genuinely interested in this.