Pressure valve

tony3619

Hello, 

Just a query about a Mains pressure valve located near the mains stopcock 

I've attached a photo and can anyone tell me..

1) is the pressure gauge measuring the stopcock side or the property pipework side? 

2) should the gauge fluctuate up and down when taps are not in use? 

3) will how open the stopcock is affect the pressure showing on the gauge? 

I know it's Abit random but this gauge use to sit at 3 bar and now it fluctuates between 2.2 and 2.6 bar and Im wondering if it's an undetected leak in the property

ThisIsWeird

1) the house side of the stopcock - from that prv onwards.

You can generally assume that the incoming mains pressure, ie the p at the stopcock, is in excess of 3bar, or else there would be no requirement to have one fitted in the first place.

The idea is that it sets the ongoing pressure to the house, limiting it to the set value, and - if the mains supply is nicely in excess of the set 3 bar - the ongoing pressure shouldn't fluctuate much from this 3 bar in use.

The needle should remain pretty constant whether a tap is being used or not. However, it shouldn't be a surprise if the needle drops to some degree when a lot of water is being drawn - if you open a huge flow, the pressure on that side is bound to collapse to some degree. Or, if the mains pressure is actually only slightly above 3 bar, then don't be surprised if it can't maintain this when a good flow is called for - expect the needle to drop a bit.

However, it should return instantly to the previous reading once the flow is stopped.

2) no, you wouldn't expect the needle to fluctuate when no water is being used. This suggests either that the mains supply is fluctuating wildly - unusual - or the previous is faulty - quite possible. 

3) in theory, if you don't draw any water, the pressure should remain constant on the gauge regardless of how open the stopcock is, because the mains supply will fill the pipes and the pressure will have stabilised, even if the s/c is only opened a bit. However, it will make a difference as soon as a tap is opened, because if the s/c is only cracked open a wee bit, the mains squeezing through will not match the demand of the open tap, so it won't be able to maintain the pressure. So, the s/c should really be fully open at all times, so it can provide the full flow as and when required, and therefore maintain the pressure.

It shouldn't be fluctuating. This could be due to the mains pressure fluctuating, or perhaps due to a sticky prv. They are pretty basic items, and are easy to open, clean, and lube with silicone grease. I can't see it being due to a leak, as it would have to be pretty major one in order to make the pressure drop!

So, to check; I'd open the s/c fully, note the static pressure, and then half open a tap. Note any pressure drop. Fully open a tap, note pressure. Close the tap - note the pressure.

Report back

tony3619

ThisIsWeird said:

1) the house side of the stopcock - from that prv onwards.

You can generally assume that the incoming mains pressure, ie the p at the stopcock, is in excess of 3bar, or else there would be no requirement to have one fitted in the first place.

The idea is that it sets the ongoing pressure to the house, limiting it to the set value, and - if the mains supply is nicely in excess of the set 3 bar - the ongoing pressure shouldn't fluctuate much from this 3 bar in use.

The needle should remain pretty constant whether a tap is being used or not. However, it shouldn't be a surprise if the needle drops to some degree when a lot of water is being drawn - if you open a huge flow, the pressure on that side is bound to collapse to some degree. Or, if the mains pressure is actually only slightly above 3 bar, then don't be surprised if it can't maintain this when a good flow is called for - expect the needle to drop a bit.

However, it should return instantly to the previous reading once the flow is stopped.

2) no, you wouldn't expect the needle to fluctuate when no water is being used. This suggests either that the mains supply is fluctuating wildly - unusual - or the previous is faulty - quite possible. 

3) in theory, if you don't draw any water, the pressure should remain constant on the gauge regardless of how open the stopcock is, because the mains supply will fill the pipes and the pressure will have stabilised, even if the s/c is only opened a bit. However, it will make a difference as soon as a tap is opened, because if the s/c is only cracked open a wee bit, the mains squeezing through will not match the demand of the open tap, so it won't be able to maintain the pressure. So, the s/c should really be fully open at all times, so it can provide the full flow as and when required, and therefore maintain the pressure.

It shouldn't be fluctuating. This could be due to the mains pressure fluctuating, or perhaps due to a sticky prv. They are pretty basic items, and are easy to open, clean, and lube with silicone grease. I can't see it being due to a leak, as it would have to be pretty major one in order to make the pressure drop!

So, to check; I'd open the s/c fully, note the static pressure, and then half open a tap. Note any pressure drop. Fully open a tap, note pressure. Close the tap - note the pressure.

Report back

So I left it over night to let it all stabilise without opening a tap etc and it Seems to sit at 2.2 bar but occasionally can go up to 2.4 bar and then drop down to 2.2 again (no outlets In use) 

Opening a tap 3/4- Full drops the gauge to 1.6-1.8 bar and when its closed it instantly goes back to 2.2 bar and moves between 2.2 and 2.4 as before. 

Does this need to looked at by a plumber? 

ThisIsWeird

It sounds as tho' your mains water supply has dropped from its previous 3bar, to the readings you are now seeing, and which are fluctuating with natural changes in the 'mains' as other folk also use water. Is the pressure lower during mornings when folk get up, and in the evenings, but higher midday and overnight? This likelihood is reinforced by the way the pressure collapses significantly when you open a tap - there is no pressure reserve there.

If your mains pressure was in the region of, say, 4 bar - which it probably was originally, and that's why they fitted a PRV - then you would expect the gauge to read the set 3 bar, and to only drop slightly below this if a large demand were made - a tap opened fully, for example. Otherwise, it should remain pretty constantly at 3 bar with the 'reserve' mains pressure keeping it going even when water is being used.

I suspect summat has gone amiss with your mains supply. A plumber should be able to confirm this by fitting their own pressure gauge directly after the stopcock. I'd warn the plumber what the issue is when you call them, so they come prepared.

Albermarle

I think some water companies have reduced their pressure, as it means we use a bit less water and there is less leakage ?
However it seems to be quite difficult to find any hard info on this .

tony3619

ThisIsWeird said:

It sounds as tho' your mains water supply has dropped from its previous 3bar, to the readings you are now seeing, and which are fluctuating with natural changes in the 'mains' as other folk also use water. Is the pressure lower during mornings when folk get up, and in the evenings, but higher midday and overnight? This likelihood is reinforced by the way the pressure collapses significantly when you open a tap - there is no pressure reserve there.

If your mains pressure was in the region of, say, 4 bar - which it probably was originally, and that's why they fitted a PRV - then you would expect the gauge to read the set 3 bar, and to only drop slightly below this if a large demand were made - a tap opened fully, for example. Otherwise, it should remain pretty constantly at 3 bar with the 'reserve' mains pressure keeping it going even when water is being used.

I suspect summat has gone amiss with your mains supply. A plumber should be able to confirm this by fitting their own pressure gauge directly after the stopcock. I'd warn the plumber what the issue is when you call them, so they come prepared.

They recently converted a derelict building into a doctor's surgery of some sort. This is about 100 yards from my house. Is it possible they are dropping the pressure threw extra usage? 

ThisIsWeird

tony3619 said:

ThisIsWeird said:

It sounds as tho' your mains water supply has dropped from its previous 3bar, to the readings you are now seeing, and which are fluctuating with natural changes in the 'mains' as other folk also use water. Is the pressure lower during mornings when folk get up, and in the evenings, but higher midday and overnight? This likelihood is reinforced by the way the pressure collapses significantly when you open a tap - there is no pressure reserve there.

If your mains pressure was in the region of, say, 4 bar - which it probably was originally, and that's why they fitted a PRV - then you would expect the gauge to read the set 3 bar, and to only drop slightly below this if a large demand were made - a tap opened fully, for example. Otherwise, it should remain pretty constantly at 3 bar with the 'reserve' mains pressure keeping it going even when water is being used.

I suspect summat has gone amiss with your mains supply. A plumber should be able to confirm this by fitting their own pressure gauge directly after the stopcock. I'd warn the plumber what the issue is when you call them, so they come prepared.

They recently converted a derelict building into a doctor's surgery of some sort. This is about 100 yards from my house. Is it possible they are dropping the pressure threw extra usage? 

Possible, but don't know.

Albermarle

tony3619 said:

ThisIsWeird said:

It sounds as tho' your mains water supply has dropped from its previous 3bar, to the readings you are now seeing, and which are fluctuating with natural changes in the 'mains' as other folk also use water. Is the pressure lower during mornings when folk get up, and in the evenings, but higher midday and overnight? This likelihood is reinforced by the way the pressure collapses significantly when you open a tap - there is no pressure reserve there.

If your mains pressure was in the region of, say, 4 bar - which it probably was originally, and that's why they fitted a PRV - then you would expect the gauge to read the set 3 bar, and to only drop slightly below this if a large demand were made - a tap opened fully, for example. Otherwise, it should remain pretty constantly at 3 bar with the 'reserve' mains pressure keeping it going even when water is being used.

I suspect summat has gone amiss with your mains supply. A plumber should be able to confirm this by fitting their own pressure gauge directly after the stopcock. I'd warn the plumber what the issue is when you call them, so they come prepared.

They recently converted a derelict building into a doctor's surgery of some sort. This is about 100 yards from my house. Is it possible they are dropping the pressure threw extra usage? 

Just for info , mains pressure of 2.5 ish is still pretty good. I think legally it only has to be minimum 1

tony3619

Albermarle said:

tony3619 said:

ThisIsWeird said:

It sounds as tho' your mains water supply has dropped from its previous 3bar, to the readings you are now seeing, and which are fluctuating with natural changes in the 'mains' as other folk also use water. Is the pressure lower during mornings when folk get up, and in the evenings, but higher midday and overnight? This likelihood is reinforced by the way the pressure collapses significantly when you open a tap - there is no pressure reserve there.

If your mains pressure was in the region of, say, 4 bar - which it probably was originally, and that's why they fitted a PRV - then you would expect the gauge to read the set 3 bar, and to only drop slightly below this if a large demand were made - a tap opened fully, for example. Otherwise, it should remain pretty constantly at 3 bar with the 'reserve' mains pressure keeping it going even when water is being used.

I suspect summat has gone amiss with your mains supply. A plumber should be able to confirm this by fitting their own pressure gauge directly after the stopcock. I'd warn the plumber what the issue is when you call them, so they come prepared.

They recently converted a derelict building into a doctor's surgery of some sort. This is about 100 yards from my house. Is it possible they are dropping the pressure threw extra usage? 

Just for info , mains pressure of 2.5 ish is still pretty good. I think legally it only has to be minimum 1

Yea I have no issues with the pressure on the outlets, my biggest worry was I had a leak between my meter on the street  and the  internal stopcock that has dropped the pressure and I'm paying for an undetected leak buried in the concrete 

ThisIsWeird

tony3619 said:

Albermarle said:

Just for info , mains pressure of 2.5 ish is still pretty good. I think legally it only has to be minimum 1

Yea I have no issues with the pressure on the outlets, my biggest worry was I had a leak between my meter on the street  and the  internal stopcock that has dropped the pressure and I'm paying for an undetected leak buried in the concrete 

There's nothing to suggest that.

You can try placing your ear as close to the PRV as possible, perhaps even using a sick - eg a chopstick - as a stethoscope, and listen for a hiss. But for a leak to cause such a drop, we'd be talking major.

Are you on a meter? If so, such a leak would be obvious on there.

tony3619

ThisIsWeird said:

tony3619 said:

Albermarle said:

Just for info , mains pressure of 2.5 ish is still pretty good. I think legally it only has to be minimum 1

Yea I have no issues with the pressure on the outlets, my biggest worry was I had a leak between my meter on the street  and the  internal stopcock that has dropped the pressure and I'm paying for an undetected leak buried in the concrete 

There's nothing to suggest that.

You can try placing your ear as close to the PRV as possible, perhaps even using a sick - eg a chopstick - as a stethoscope, and listen for a hiss. But for a leak to cause such a drop, we'd be talking major.

Are you on a meter? If so, such a leak would be obvious on there.

I was thinking a leak more underground between the curbside and my meter so it wouldnt be detected other that a lower pressure on the gauge or a high bill. I wouldn't even know where my meter is