Boiler Losing Pressure Following Mains Meter Install

GazzaGazza · 19 Sep 2019

Hi

I had a new Worcester Greenstar 30i ErP condensing combi fitted around 18 months ago and have had no problems with it at all. Last week I went on holiday for a week and during that time, the water company turned up and fitted a water meter. Since I returned, the water pressure in the boiler has been dropping to zero. When I top the boiler up to 1.5/2 bar, it is back to zero within around 6-9 hours.

I've checked throughout for leaks and for now there is nothing visible I can see.

I appreciate it's a closed-loop system, but is there anything that is perhaps needed on the boiler to support a water meter that wasn't installed at the time it was fitted to the normal mains?

Cheers
Gaz

undertrained · 19 Sep 2019

Have you checked to see if filling loop open? It may have been knocked?

GazzaGazza · 19 Sep 2019

Yep, checked. I'm constantly opening it to re-pressurise and then closing it off again.

dilalio · 20 Sep 2019

Pressure it up and then carry out the normal checks on the discharge pipe from the PRV.

Did you happen to also put the heating on for the first time since start of summer?

undertrained · 20 Sep 2019

Pressurise it, and disconnect loop, upon disconnecting check for valves passing.

sbgasman · 20 Sep 2019

undertrained said:
Pressurise it, and disconnect loop, upon disconnecting check for valves passing.

if the filling loop was passing the pressure would increase not drop to zero

GazzaGazza · 20 Sep 2019

dilalio said:
Pressure it up and then carry out the normal checks on the discharge pipe from the PRV.

Did you happen to also put the heating on for the first time since start of summer?

Done that, no water coming through discharge pipe.

Heating was on for the odd day/night a few weeks leading up to me going away/the meter being installed. No problems as I made sure to check the pressure regularly with it not being used iver the summer.

GazzaGazza · 20 Sep 2019

There seems to be some discussions on the internet about water meters having a non-return valve and that boilers should have some sort of expansion vessel fitted?? When the boiler was installed, it was on the mains and therefore I’m not sure if the engineers fitted this. Not sure if this would make a big difference or not.
But with my limited knowledge, I’d say that if the meter does have a non return valve and the boiler doesn’t have an expansion vessel, there would be increased pressure on the internal pipe work/system and could cause a leak at any weak spot. However, no evidence of leaks.

dilalio · 21 Sep 2019

GazzaGazza said:
Done that, no water coming through discharge pipe.

Did you put a plastic bag/balloon/latex glove over it and check over the time that the pressure drops?

dilalio · 21 Sep 2019

GazzaGazza said:
There seems to be some discussions on the internet about water meters having a non-return valve and that boilers should have some sort of expansion vessel fitted?? When the boiler was installed, it was on the mains and therefore I’m not sure if the engineers fitted this. Not sure if this would make a big difference or not.
But with my limited knowledge, I’d say that if the meter does have a non return valve and the boiler doesn’t have an expansion vessel, there would be increased pressure on the internal pipe work/system and could cause a leak at any weak spot. However, no evidence of leaks.

Your CH system is sealed (a closed circuit) and is separated from the mains via the valves either side of the filling loop (which should actually be removed when not in use - but they rarely are).

As such, any fluctuations in mains pressure will not affect the pressure within the closed circuit.

There will be an EV within your boiler and its purpose is to absorb the expansion of water, in the closed circuit, as it heats up.

If you are losing pressure, this will likely be due to the EV needing recharging with air because, if it's depleted, it will not provide expansion and the pressure rise will cause the PRV to lift and release excess pressure via the discharge pipe.

Or you have a leak somewhere on the closed circuit.

bernardgreen · 21 Sep 2019

sbgasman said:
if the filling loop was passing the pressure would increase not drop to zero

With the filing loop removed the valve could be passing in the opposite direction to the filling direction.

dilalio · 21 Sep 2019

bernardgreen said:
With the filing loop removed the valve could be passing in the opposite direction to the filling direction.

No, they have an in-line check valve to prevent contamination of the mains supply.

GazzaGazza · 21 Sep 2019

dilalio said:
Did you put a plastic bag/balloon/latex glove over it and check over the time that the pressure drops?

Yep, nothing in it. Thanks for the tip.

GazzaGazza · 21 Sep 2019

dilalio said:
Your CH system is sealed (a closed circuit) and is separated from the mains via the valves either side of the filling loop (which should actually be removed when not in use - but they rarely are).

As such, any fluctuations in mains pressure will not affect the pressure within the closed circuit.

There will be an EV within your boiler and its purpose is to absorb the expansion of water, in the closed circuit, as it heats up.

If you are losing pressure, this will likely be due to the EV needing recharging with air because, if it's depleted, it will not provide expansion and the pressure rise will cause the PRV to lift and release excess pressure via the discharge pipe.

Or you have a leak somewhere on the closed circuit.

Thanks for this. It’s what I was thinking all along. But I’m just a bit puzzled as to why this all started at the same time as they put a water meter on the mains supply. Just a coincidence with some sort of leak somewhere that’s happened at the same time. Thanks for the info.

ianmcd · 21 Sep 2019

bernardgreen said:
With the filing loop removed the valve could be passing in the opposite direction to the filling direction.

If the filling loop is removed what magic allows water to pass between systems ?

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Boiler Losing Pressure Following Mains Meter Install

undertrained

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