My Potterton boiler keeps losing pressure and I don't know why

[James Cridland]

Greetings,

I have a Potterton Promax Combi HE Plus, which was installed by British Gas around three years ago. (Don't get me started on the quality of the installation...) It replaced an older boiler which wasn't a condensing boiler; the radiators weren't replaced.

This boiler is forever losing system pressure, and it's getting to be quite irritating.

System pressure doesn't gradually decline: it appears to stay constantly at 2-ish for two days or so, and then the next time I look at it it's dropped to 0.5, flashing the familiar "E1" display. The drop isn't related to the time of day, and sometimes happens much quicker.

The central heating system is not, as far as I can tell, leaking; and neither my repeated visits from British Gas or an independent plumber has been able to spot any evidence of a leak.

Turning both taps off to the central heating system doesn't appear to fix this issue; though it behaved itself remarkably over summer.

I can see the flue of the boiler out of the back of the house (it's an upright one) and it does appear to always have quite a lot of steam coming out of it. After the morning heating cycle, there's enough condensed water to have made a small pool at the bottom of the flue itself. I don't know enough to know whether this is expected from a boiler of this type.

British Gas have, variously, completely changed the electronic circuit-board; fitted a MagnaClean (quite how that was supposed to help I've little idea); cleaned the heating elements after the thing started chugging a lot when making hot water; and replaced the pressurised big red thing inside.

The pressure-release valve only drips water when the pressure is above 3; and otherwise doesn't. It does not show any signs having dripped after the pressure mysteriously plummets (it's outside, and drips onto tile).

Does this ring any bells with anyone here as to what's wrong? The traipsing downstairs in a freezing house in a dressing-gown to repressurise is beginning to get me down...

I'm in London N14, if that's of any use.

 

[GPSNewcastle]

Have you definitely looked at the central heating pipework throughout the entire property to ensure that there arent any leaks?

 

[James Cridland]

Have you definitely looked at the central heating pipework throughout the entire property to ensure that there arent any leaks?

Many thanks for your help.

I have done. Some of the pipework is in concrete, so it's hard to look at that bit; but all the visible pipework has been checked, and it can lose pressure three or four times a day; that should mean considerable amounts of water leaking somewhere, and I've not been able to see it. (A plumber and I have done quite a lot of ripping up floorboards too).

The question is... if I turn both taps for the central heating off, why does it still lose pressure?

 

[wards]

prv would be my initial suspect,tie a bag over the prv and monitor it over a few days,if you then discover water has collected you will know that is the problem,if not at least you have eliminated that and can move on to other possibilites to the cause.HTH

 

[cjg]

prv would be my initial suspect,tie a bag over the prv and monitor it over a few days,if you then discover water has collected you will know that is the problem,if not at least you have eliminated that and can move on to other possibilites to the cause.HTH

looks that way to me to, if taking presure up to /over3bar then it will open ,weep,/leak on the prv, olso you will find that it takes only a little bit of grit in the prv and it will drip, if this is the case then you are better off changing it chris.

 

[Paulplumb]

Surely he would have checked/noticed the prv discharge pipe. How old are those copper pipes set in concrete?

 

[GPSNewcastle]

Read this point lads "The question is... if I turn both taps for the central heating off, why does it still lose pressure?"...he has turned off the valves on the boiler which means the PRV definitely isnt the problem....he has a leak but hasnt found it yet. The one thing you have to take into consideration is the amount of water lost....put a bucket under ur PRV termination outside and blow the boiler off from 1.5bar to 0 bar....it isnt as much water as you thought is it?

 

[James Cridland]

Read this point lads "The question is... if I turn both taps for the central heating off, why does it still lose pressure?"...he has turned off the valves on the boiler which means the PRV definitely isnt the problem....he has a leak but hasnt found it yet. The one thing you have to take into consideration is the amount of water lost....put a bucket under ur PRV termination outside and blow the boiler off from 1.5bar to 0 bar....it isnt as much water as you thought is it?

Happy to double-check the PRV, but, as I say, I'm not really seeing any water coming out of it.

Two things I don't understand...

First, why if I close the valves to the central heating system, it still has a pressure loss: so I don't quite understand how it can be a leak in the central heating system.

Second, where is the water coming from that is steaming out of the flue? Should I have enough water there to collect as a puddle after just an hour's use in the morning? Is this all condensation from the atmosphere... or is this coming from the boiler's system somehow - and if so, where?

I'm a little ignorant about how this boiler works, being honest...

Thanks for your input: very much appreciated.

 

[Gray0689]

Don't worry about the flue that's normal
You have a leak it's just in a area it's not showing
When you turn valves off all your doing is turning off your flow and return pipwork from boiler
But still check prv

 

[justlead1]

Chek expansion vessel is charged up.

 

[fireblade]

Could be heat exchanger on boiler losing pressure down the condense pipe had the same thing on a three year old worcester

 

[Billy Bob Bob]

highly unlikely on this boiler i would be checking prv and expansion vessel worth noting on this boiler it has been known for the expansion vessel to crack on its casing but this would cause a very noticeable flood also the valves could be passing pointing the fault back on the system

 

[Brutha]

highly unlikely on this boiler i would be checking prv and expansion vessel worth noting on this boiler it has been known for the expansion vessel to crack on its casing but this would cause a very noticeable flood also the valves could be passing pointing the fault back on the system

I have seen two of these pinholed already.

Turn the boiler off, fill it up and see if anything runs out the condense pipe. If it does you have your culprit.

 

[Billy Bob Bob]

they might if sentinel feroquest is fitted but i myself or any of the heat-team field engineers i know have never seen this happen

 

[Brutha]

Fair enough but it is a British gas installation... Chances are the system wasn't flushed properly, if at all.

I work for BG and see this on their installations. Maybe its something their using and for the most part BG are changing heat exchangers before we have to go to you guys for help!

 

[James Cridland]

You have a leak it's just in a area it's not showing. When you turn valves off all your doing is turning off your flow and return pipwork from boiler

But if I'm turning those valves off, surely the central heating pipes are isolated, and therefore even if there was a leak in those pipes, surely it wouldn't drop in pressure?

 

[cjg]

are the flow and return valves fully off, as some times you think they off but you have to give some that little tiny bit more and some not all (click) into place,

But if I'm turning those valves off, surely the central heating pipes are isolated, and therefore even if there was a leak in those pipes, surely it wouldn't drop in pressure? ( i would say correct) if the guage is in the boiler side,

 

[jimmygplumbheat]

If the leak is inside the boiler then when you shut the valves off the pressure reading is that of the pressure in the boiler. so pipes aren't likely to be the answer. thats why its still saying its losing. more than likely the PRV or expansion chamber. due to the heat in the boiler its difficult to spot minor leaks as they evaporate away. also not a great deal of water is needed to be lost to lose the pressure.