Water meter and combi boiler back pressure

[Steelmasons]

Call a plumber.

 

[picasso]

1000 metres ? a kilometre ? thats over half a mile of under floor heating pipe on an 8l expansion vessel.

 

[kam187]

Right, but the supplier told me to use length * 0.113 to get volume in litres = 113 litres approximately. Also the system was cold with that back pressure issue. So although it's an easy thing to point to as the cause it's not very likely.

 

[picasso]

You need someone on site, as already said call a plumber.

 

[kam187]

Spoke to my plumber who re-installed the boiler after the underfloor went in. All that's changed as i said was the expansion vessel and the PRV. He's baffled.

 

[Agile]

Can you post a photo of the baffled plumber?

 

[Agile]

When setting that type of pressure reducing valve you need to do it with a small forward flow through it.

Say 1 li/min in your case.

Tony

 

[FurstyFerret]

Where are you measuring your water pressure? If there's a double-check valve between your pressure gauge and the system you won't get accurate results (except for the very first measurement).

 

[picasso]

Completely lost me, one minute the OP is on about his mains water pressure and the next his ufh, then it's hot water coming out the cold tap .

 

[nortonj]

Completely lost me, one minute the OP is on about his mains water pressure and the next his ufh, then it's hot water coming out the cold tap .

Glad its not just me then

 

[Nozzle]

The most screwy thing about this is... the incoming pressure is 3.3 bar, and you're managing to see 6 bar pressure without adding any heat. THAT right there is magic.

Nozzle

 

[bernardgreen]

Is the gauge failing to accurately report pressure ?

 

[NuaghtyNigel]

The most screwy thing about this is... the incoming pressure is 3.3 bar, and you're managing to see 6 bar pressure without adding any heat. THAT right there is magic.

Nozzle

Firstly, 3.3 bars sounds slightly low to me unless it is measured with water flowing. 4 or 5 bars is more usual.

At a guess, if there is a non-return valve somewhere in the system, (the water meter has been mentioned), a sudden stoppage of flow by (say) a washing machine or dishwasher inlet valve will result in a transient increase in water pressure owing to the mass of water flowing through the pipes. This is often heard as a 'bang' when an electric shower or washing machine valve switches off. An expansion vessel will absorb this to a point, but will effectively store the energy (pressure) as there is nowhere else for it to go.

It is also possible that the mains pressure is fluctuating owing to local demand.

 

[Agile]

Firstly, 3.3 bars sounds slightly low to me unless it is measured with water flowing. 4 or 5 bars is more usual.

If a mains pressure of 3.3 bar sounds low to you then you should visit some properties in London.

Many even at ground level are barely over 1.3 bar.

Filling a combi fitted on upper floors can take ages.

I have a client who has a flat on the third floor and shares the mains supplies with lower flats. His water flow reduces to zero when anyone else in the building takes water.

The EHO has served a notice on the freeholder to get them to fit a dedicated mains supply just to his flat. But nothing seems to be getting done. Flats were converted about 20 years ago and should have had individual supplies then but seems it was overlooked.

The client I go to is only a disabled tenant and has no money so cannot explore improvements like an accumulator.

Tony

 

[Biggles..]

@Steelmasons @Dan Robinson @gas112
Loving this, the top 100 struggling with the basic concepts of how to set a pressure reducing valve.