how does a pressure reducing valve funtion??

johnjoe 123

hi folks i have fitted a lot of pressure reducing valves but am baffled as to how they work??? i know a gate valve can restrict flow but not pessure! help me out!!:o

JohnnieK

Why dose the sun rise? It just dose. Ah only joking. When the pressurized water comes in it acts on a spring inside the valve which closes the valve so a lower pressure leaves the valve. Different rated valves have a tighter or looser spring in them. I think that's it but I'm open to correction on it.

Joey the lips

This is a strange question for a plumber to be asking but good. I have had many plumbers ask for a pressure reducing valve and what they really want is an auto fill valve. Needless to say I feel an auto filling valve should be banned as when the pressure of the system falls below a certain point it tops it up. This has the ability to mask leaks which ofcourse is very dangerous.

JohnnieK

Joey the lips wrote: »

This is a strange question for a plumber to be asking but good. I have had many plumbers ask for a pressure reducing valve and what they really want is an auto fill valve. Needless to say I feel an auto filling valve should be banned as when the pressure of the system falls below a certain point it tops it up. This has the ability to mask leaks which ofcourse is very dangerous.

I totally agree with you on this one Joey. I hate them. What's wrong with a filling loop???

steamengine

johnjoe 123 wrote: »

hi folks i have fitted a lot of pressure reducing valves but am baffled as to how they work??? i know a gate valve can restrict flow but not pessure! help me out!!:o[/QUOTE


Copied this over from WIKI, bit off scale for a small valve, but it shows the principle of how they work. The outlet water pressure acts on the diaphragm to control flow via the valve, and also maintain the set pressure. The outlet pressure is adjustable via the spring.

Micky Dolenz

Joey the lips wrote: »

This is a strange question for a plumber to be asking but good. I have had many plumbers ask for a pressure reducing valve and what they really want is an auto fill valve. Needless to say I feel an auto filling valve should be banned as when the pressure of the system falls below a certain point it tops it up. This has the ability to mask leaks which ofcourse is very dangerous.

Very dangerous? How so in your opinion?. Feed and expansion tanks could do the exact same thing.

They have been banned in the UK for years. No RGI would fit them to a gas boiler, if they fit as per manufactures instructions which I am sure they all do.

Micky Dolenz

johnjoe, Volume and pressure are different things as you have correctly established. If you pass one bar through a 10 mm pipe it would spray all over the place because there is significant pressure being apply to a small volume of water. Increase the size of the pipe and the water flow seems to slow, It is the by product of the same amount of pressure being applied to a larger volume of water. Stick a gauge on each and you will get a reading of 1 bar.

So, a reducing valve has to control volume and pressure to give a constant end result. In the above schematic, which is useful, the diaphragm works constantly to achieve a balance across the valve, pre-set by the spring. This happens very quickly.

Always ask questions, you will always be learning the trade.

Joey the lips

Micky Dolenz wrote: »

Very dangerous? How so in your opinion?. Feed and expansion tanks could do the exact same thing.

They have been banned in the UK for years. No RGI would fit them to a gas boiler, if they fit as per manufactures instructions which I am sure they all do.

dangerous because they are used to mask leaks. I suppose if the leak is in a nice pce of 1 meter pipe at the back of the kitchen sofa its fine but they are usually under a tiled bathroom floor leaking against a ceiling joist or at the back of a cylinder leaking onto the kitchen ceiling just under the spot where mrs murphy sits with all her visitors.

johnjoe 123

thanks every1 and you are rite mickey if only joey would take a leaf out of your book haha just kiddin joe!!