Huge pressure difference in different areas of the property

[arranjj]

I have a strange one:

Big property, 22mm meter in a manhole, going to an underground pipe. Then an underground tee so that I have 2 pipes rising out of the ground in seperate buildings, each with a 3/4 inch stopcock. 1 reads 2.9 bar, the other reads 1.1 bar. How can that be?!

Yes if I turn the main stopcock off nothing comes out of either of the two buildings, and with it on it does. I have taken multiple readings throughout the day with nothing in use - one is farily consistent reading 2.1-2.9 bar, the other is 1.1 bar, down to 0.5 at times.

Many thanks in advance!

 

[Agile]

An underground leak ???

That would indicate a very significant leak! Perhaps 10-20 litres/per minute.

The answer, if you dont have a water meter, is to nearly close each stopcock and listen with a stick and see if you can hear water flowing.

Tony

 

[rojaca]

What are you using to take these measurements (e.g fixed pressure gauges on the pipework)?
Have you tried a tightness test with the main stopcock turned off?

 

[arranjj]

I'm assuming I'd probably not get a fairly consistent 2.9 bar and 20+ l/m on the other stopcock though if that were the case. I only have a 22mm supply.

 

[picasso]

another tee off the pipe with the lower pressure , maybe somebody has tapped into your supply for free water

 

[arranjj]

Yes I'm using a Monument pressure tester on a piece of flexi hose. Screwed into the outside tap on the one reading up to 2.9 bar, and tried the outside tap on the other building to get 1.1 bar, then tried directly onto the 22mm pipe coming out of the stopcock to get 1.1 bar too.

I haven't tried the tightness test, nor have I even tried looking at the meter dials (difficult to do, but I can try in the morning). My bills are not exceptionally high, and this has been the case for a long time.

I have taken readings at 3am - same results - 2.9 and 1.1 - so unlikely to be the neighbours! - Again such a difference wouldn't make a lot of sense.

I am correct in thinking a fauly stopcock would not change the pressure reading at all?

 

[tamz]

Sounds like a leak to me or maybe as picasso said

Even if one pipe had a blockage or kink the static pressure would be much the same.
Did you try swapping over the guages to the different supplies. Might be faulty guages.

 

[arranjj]

I am using the same gauge

 

[picasso]

are we talking dynamic pressures here ? if so a restriction in the pipe will drop the pressure and flow.

 

[arranjj]

At 3am I can assume nothing is using any water. I am attaching the gauge. It is giving me a reading. I turn a tap on and it drops, then I turn the tap off and it goes up again (same reading).

 

[picasso]

the reading with the tap off is the static pressure, this will be the same at both taps, the reading with the tap on will be lower, this is the dynamic pressure, this reading is affected by pipe length , bends , kinks , restrictions and diameter of the pipes, so it will be different as there is probably some kind of rectriction in the pipework .

 

[Agile]

Its obvious really!

You have a buried pressure reducing valve on one side of the supply!

You meantioned a "buried tee". How can you know this?

The second property may be supplied form a completely different source in a different direction. Not that unusual on country properties.

Original is insufficient so a new supply is fitted to a new mains from the opposite direction.

Tony

 

[arranjj]

The issue is with the static pressure. 1 is 1.1, the other (much closer to the meter) is 2.9.

I am assuming a buried tee because both buildings have black pipe coming out of the ground to a stopcock, and when I turn the main stopcock on the meter off both buildings stop.

I can't think of a reason why there would be a pressure reducing valve buried in the ground, but could there be an underground problem that simulates the effect of a pressure reducing valve (that would affect static pressure?)

 

[picasso]

nope, if the pipes are connected together then the static pressure will be the same, it looks like you have a prv underground somewhere. unless of course one of the taps is 20 meteres above the other.

 

[arranjj]

Same height taps. And I can't think why there would be a PRV underground given the age of the property/pipes. Is an underground PRV commonplace?