Pressurised Heating System Losing Pressure
Discussion
House was refurbished and new heating system was working fine - holding 1bar when cold for the last 6 months.
When the extension was recently completed, meaning an extra 3 rads (total of 15) we had issue of the 12L expansion vessel not being large enough so the pressure valve allowed the excess to overflow.
So I fitted a larger vessel (18L on the basis that if the built in one went, it could still cope) and now the max pressure is only 1.25 bar hot but overnight it will still lose pressure to zero.
I understand the pressure valve can carry on leaking once activated so I cleaned it and have hung a bucket from the overflow and it's definitely not leaking now.
But the last 3 days it's dropped from 1bar to zero overnight.
90% of the new plumbing is exposed and if the last 10% was leaking at least 1 litre a night I'd surely have seen it by now.
What else could it be ?
I can isolate the boiler from the system or from the new extension to see what happens but I'm sure I'm missing something.
It only takes around 10 seconds to raise the pressure from 0 to 1 bar and I'm sure it used to take longer - it's a big system with the average rad being 1800x600 P+ so that doesn't seem right.
When the extension was recently completed, meaning an extra 3 rads (total of 15) we had issue of the 12L expansion vessel not being large enough so the pressure valve allowed the excess to overflow.
So I fitted a larger vessel (18L on the basis that if the built in one went, it could still cope) and now the max pressure is only 1.25 bar hot but overnight it will still lose pressure to zero.
I understand the pressure valve can carry on leaking once activated so I cleaned it and have hung a bucket from the overflow and it's definitely not leaking now.
But the last 3 days it's dropped from 1bar to zero overnight.
90% of the new plumbing is exposed and if the last 10% was leaking at least 1 litre a night I'd surely have seen it by now.
What else could it be ?
I can isolate the boiler from the system or from the new extension to see what happens but I'm sure I'm missing something.
It only takes around 10 seconds to raise the pressure from 0 to 1 bar and I'm sure it used to take longer - it's a big system with the average rad being 1800x600 P+ so that doesn't seem right.
55palfers said:
I have the same problem. We had two extra rads fitted last year. Not sure if the plumber put in a bigger expansion vessel though.
Almost every day I have to top up the system with water.
It seems to be producing more condensate too.
Losing water/pressure with no obvious leaks and an increase in condensate usually means the heat exchanger in the boiler unit is leaking. New boiler time.Almost every day I have to top up the system with water.
It seems to be producing more condensate too.
55palfers said:
I have the same problem. We had two extra rads fitted last year. Not sure if the plumber put in a bigger expansion vessel though.
Easy way to tell if it's causing a problem, is to watch your pressure gauge - when hot if it goes over 2.5bar it's probably leaking via the safety valve to the overflow (or just check the overflow).V8RX7 said:
Not that I'm aware of.
I did have when I had to keep topping it up before I fitted the new exp vessel and I was surprised that after fitting it, I've kept going around the rads and have got very little air out.
Don't rule it out, if it's not going out of the prv and you have no leaks then that's where it will be going. Pop the tank out and test it by pumping it up is the best way to check.I did have when I had to keep topping it up before I fitted the new exp vessel and I was surprised that after fitting it, I've kept going around the rads and have got very little air out.
V8RX7 said:
It only takes around 10 seconds to raise the pressure from 0 to 1 bar and I'm sure it used to take longer - it's a big system with the average rad being 1800x600 P+ so that doesn't seem right.
Daft question but I'm assuming you watch the gauge or revisit it after a few minutes - if you top ours up, it'll register straight away on the pressure gauge, but then gradually sink back a bit as the system takes some of the slack up, if you see what I mean. Takes a couple or three goes to get it topped up to a certain constant pressure reading - a large-ish system with ufh, a thermal store and two exp vessels.I had a lot of problems with my heating system last year losing pressure, I found a small leak and sorted that out but the pressure still dropped over a few days , I had the boiler people out and they said it was my system leaking I have whole house underfloor heating so miles of pipework.
I eventually closed off the flow and return valves under the boiler and the pressure was definitely leaking via the boiler so i called them out again and showed them the drop test and the boiler man said he would look at the heat exchanger but doubted it was that as the boiler was still quite new.
Anyway on stripping it down it was caked in scale as it leaked into the combustion chamber and the water was evaporated by the flames of the boiler.
So check by closing off the boiler from the system for a while and see if the boiler or the system drops in pressure at least you have an area to look at.
I eventually closed off the flow and return valves under the boiler and the pressure was definitely leaking via the boiler so i called them out again and showed them the drop test and the boiler man said he would look at the heat exchanger but doubted it was that as the boiler was still quite new.
Anyway on stripping it down it was caked in scale as it leaked into the combustion chamber and the water was evaporated by the flames of the boiler.
So check by closing off the boiler from the system for a while and see if the boiler or the system drops in pressure at least you have an area to look at.
Busterbulldog said:
V8RX7 said:
Not that I'm aware of.
I did have when I had to keep topping it up before I fitted the new exp vessel and I was surprised that after fitting it, I've kept going around the rads and have got very little air out.
Don't rule it out, if it's not going out of the prv and you have no leaks then that's where it will be going. Pop the tank out and test it by pumping it up is the best way to check.I did have when I had to keep topping it up before I fitted the new exp vessel and I was surprised that after fitting it, I've kept going around the rads and have got very little air out.
He hasn't answered me either.
I think he knows what he's done don't you?
andy43 said:
V8RX7 said:
It only takes around 10 seconds to raise the pressure from 0 to 1 bar and I'm sure it used to take longer - it's a big system with the average rad being 1800x600 P+ so that doesn't seem right.
Daft question but I'm assuming you watch the gauge or revisit it after a few minutes - if you top ours up, it'll register straight away on the pressure gauge, but then gradually sink back a bit as the system takes some of the slack up, if you see what I mean. Takes a couple or three goes to get it topped up to a certain constant pressure reading - a large-ish system with ufh, a thermal store and two exp vessels.I'll go back after an hour and there's no change but by the next morning it's around zero
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