went for a new ideal boiler with 10yr guarantee (in our house that we rent out to my daughter). since its been installed the system keeps losing pressure. plumbers been round a couple of times and thought hed sorted it, but it keeps losing pressure maybe 7 or 8 times a day and my daughter has to keep opening a tap or something to build the pressure up again.

googling and friends advice seems to suggest a leak somewhere, its a lot higher pressure now than the old boiler. the plumber says he checked all the pipes in the loft for leaks and the only thing ive got to go on is that apprently the bathroom radiator never gets hot even tho its turned on.

could it be trapped air, so just needing a bleed? that still doesnt cure a leak tho.
if i go round the radiators bleeding them all, do i need to do it in a certain order (furthest from boiler first possibly) with the heating turned off?

any help much appreciated. oh, and ill be contacting plumber about it monday, just getting the christmas/new year break out the way.

thanks

EDIT: also just to point out shes already had the Ideal chappy out as part of the guarantee. they checked the boiler and installation and given it the ok. theyve said the fault is in the old system somewhere.

putting a new boiler on an old system can be a bollocks.

i had a number of small leaks that didnt show up to the naked eye when i went from a gravity fed to pressured system.

adding some uv dye to the system and checking every connection with a uv light soon showed up some poorly soldered joints in the old pipework…..

Yes, you’ll be surprised just how small a leak can be and still result in frequent loss of pressure.

We spent an entire winter losing pressure every couple of days, it wasn’t until the heating was turned off for an extended length of time that we discovered a tiny leak from an upstairs radiator. Whist the heating was on it was evaporating away so no evidence of the leak.

As trail rat said, sounds like leaky pipework, air in the system would result in cold radiators but once at a stable pressure would stay that way. If the radiator you mention is always cold try bleeding it first to eliminate air in it and if its still cold then the leak is probably somewhere at its inlet feed, if it was at the outlet then the radiator would heat but the system would still lose pressure somewhere after it. Could be the leak is under the ground floor but directly above the bare ground so a leak will go unnoticed as its just draining to the ground and not to a wall or floor etc..

The pressure vessel is charged isn’t it?

Bleed your radiators after topping the water up in the system.

If you have a lot of air the system it will make the leak appear much worse.

If you are topping up the system to the green section on the pressure gauge and there is air in there, all you are doing is compressing the air.

Top up, bleed and the pressure will drop again. Repeat until no air comes out of any of the radiators. I don’t thin it matters much what order you do it in. Just keep bleeding until all the air is gone.

You will find that you may only have to top the system up every couple of months if it’s a small leak.

Leak in hot water tank?

If the above fails chuck a can of this into the system:
http://www.screwfix.com/p/fernox-f4-express-leak-sealer-265ml/61837

Fixed the problem with a tiny leak I couldn’t track down – been over a year now and pressure not budged from 1 bar.

mmmmmmmmm voided warrenties ahoy…..

7 or 8 times a day sounds a lot :(. Does it still leak at the same rate with the boiler off?

The pressure vessel is charged isn’t it?

or maybe is too small? Does sound like a leak though

just had a mate over who’s a plumber, said hed give it a quick look. hes found out that the blow-off pipe is leaking substantially to outside. he said thats a boiler problem and shouldnt be happening, and yes, its the pressure vessel thats filling with water or something?

ill get on to Ideal on monday, but he says theyll probably try and blame the plumber. to me tho it sounds like a cast-iron boiler issue.

thanks for the help

Might want to make sure the drain valve is closed of course….

Just asked my mate that, he says you’d have to get inside the boiler to check, but still thinks it’s the pressure vessel cos of the pressure rise. (It went up to nearly 3 bar at one point)

mmmmmmmmm voided warrenties ahoy…..

Good point, my boiler is well out of warranty.

The reason I mentioned it is ours failed after a year. Theres a bladder inside a tank. The bladder contains air at a certain pressure, when the water in the system expands the air compresses. If there is no air in it the excess pressure is relieved by dumping water outside. It’s a simple job to pump up, there’s a schreader valve on the vessel. However it water comes out when you press the pin in the valve the bladder has failed. I’m not sure whether a new boiler would ship with the vessel pressurised. It doesn’t takemuch though, about 15 psi I think mine is. However it needs doing with no pressure in the boiler. I used a shock pump to pump mine up which was a bit overkill pressure wise.

…and check the valvecore is in properly 🙂

Did the same with all the suggestions and found a part on the boiler needed replacing as it had become clogged.

If it needs topping up 7 – 8 times a day its not a small leak. Things to check.

You will have a small copper pipe outside pressure relief pipe. Check that this is dry when running and when turned off.

Another thing you can do is top up the boiler to the correct pressure. Turn it off and then turn the 2 isolation valves off at either side of the boiler. Do this for as long as you can. Try at least half a day but if it needs topping up as much as you say it probably wont need it. If the pressure holds on the boiler and then you open the valves and it drops you know the system had a leak on it.

. It’s a simple job to pump up, there’s a schreader valve on the vessel.

…and check the valvecore is in properly

dont really want to investigate myself, i dont know what im doing and i dont want to invalidate the warranty. surely they have to fix it themselves?

You will have a small copper pipe outside pressure relief pipe. Check that this is dry when running and when turned off.

yep, as mentioned above, plumber has discovered this is where its leaking from.

Another thing you can do is top up the boiler to the correct pressure. Turn it off and then turn the 2 isolation valves off at either side of the boiler. Do this for as long as you can. Try at least half a day but if it needs topping up as much as you say it probably wont need it. If the pressure holds on the boiler and then you open the valves and it drops you know the system had a leak on it.

Ideal did this and said the boiler was fine, it kept pressure. but then when ‘the system’ was introduced again the pressure fell.
so that to me (with no plumbing knowledge at all) suggests the systems at fault, yet the leaking blow-off pipe suggests a boiler fault :-/

thanks

Does it need topping up each time the system has been hot and cools down again?

If the bladder in the expansion vessel has failed then you would top the system up to operating pressure, the heating would come one and the system would weep out excess pressure through the safety valve. Then, when it cools down the pressure would drop.

Oh and that fernox leak sealer, I had a small leak under a freshly tiled floor and fixed things a treat!

just an update to this.

ideal engineer coming round again today, much to his disgust as “ive been an engineer for 20 years, i know what im talking about, ive told you, its not the boiler”
i cobbled up a little test yesterday, tied a plastic beaker underneath the pressure relief pipe on the outside of the wall.
this morning the system has lost pressure again and the beaker is nearly full. hopefully that will mean something to the engineer.

i asked my daughter again if theres any rhyme or reason to when it loses pressure, she says not. can be 3 times a day, 8 times a day, when the heatings on, when its off…..
overnight theres nothing on, no heating or call for water, and it loses pressure every night, its gone every morning.

Is the PRV in the boiler or elsewhere in the system? If it’s opened due to excess pressure (expansion vessel empty etc) then it should be replaced.

Can I just ask, if the PRV has operated to release excess pressure then it MUST be replaced? Or is it just best practice?
Surely its just a spring loaded valve, so should be capable of operation a number of times? Or is it just because they rarely move and once operated have a habit of not sealing again properly?

Surely its just a spring loaded valve, so should be capable of operation a number of times? Or is it just because they rarely move and once operated have a habit of not sealing again properly?

This – it takes a tiny amount of debris to stop it from completely closing. I’m sure it’s possible to clean them out – but I imagine it’s a lot less hassle to simply swap them out if they are weeping.

I’ve no idea where the valve is, I’m no plumber 🙂

Sat here now waiting for engineer. Weirdly, the pressure has dropped again since daughter left this morning, but there doesn’t seem any more water in the cup which has baffled me. Hopefully it’ll mean something to the engineer.

I’ve topped the pressure up again so hoping it’ll Starr dripping while he’s here.

Still waiting, so been having a play. Switched heating on, pressure stayed at around 1.5 bar for 10 mins or so. Then it started climbing, up to around 3 bar, that’s when the magic happened and the pressure relief valve must have kicked in and started dripping water into my cup.

Switched heating off, drips stopped, pressure dropped to 1.5 again. I assume if I’d left heating on pressure would have stayed 3 bar for longer, possibly being topped up by extra water? Dont know. Then when heating goes off it drops right down to zero.

Does that make sense to anyone? Boiler issue or system?

Thanks

Expansion vessel empty would be my guess – though someone did actually tell you how to check it early on in the thread.

Sounds very similar to the issue im having with my central heating system.
It was losing pressure whenever it was used. Turns out it was the expansion vessel had no pressure (no water out the schraeder valve fortunately), so once things warmed up the pressure increased and the PRV kicked in and dumped the water.
I increased the pressure to around 7psi which has improved things, but its still losing a little water from the PRV when then pressure gets too high. Having read up a little more, the expansion vessel needs pumping up to 10psi, which I still need to do.

I had the same when the flexible braided hose to the expansion vessel got blocked. Cleaning out the hose which was full of a hard black precipitate solved the problem.

Ours had two expansion vessels (#boastoftheday)
but the pipe linking them to the system was blocked, so all testing and re-pressurising of the expansion vessels did not work – took a while to locate that issue

Which reminds me – need to get a power flush or British gas wont come round to fix it again.

Expansion vessel empty would be my guess – though someone did actually tell you how to check it early on in the thread.

tis true, but even with instructions i was loathe to touch something i havent a clue about. when its under warranty especially.

I had the same when the flexible braided hose to the expansion vessel got blocked.

bingo! or i hope it is! engineer is putting that as his best guess. hes also changed the PRV (or safety valve as he insisted it was called) just to be on the safe side. certainly since he left, pressure hasnt risen in 40 mins or so. ive left it now so will have to rely on daughters reports tonight.

he was a little scathing about my installer, even tho he’d originally insisted it couldnt be the boiler and must be ‘the system’.
“the dirt wasnt in there when it left the factory” and also the ‘filter/inhibitor’ or whatever its called has been installed ‘on the flow side rather than the return, so theres nothing to stop sh*t going through the boiler’.
that may or may not be true, i iz ignorant.

Well properly draining the water out of the system so there was no residual pressure left in there and then repressurising the expansion vessel to the correct pressure has sorted mine a treat. I drained probably 5-7 litres of water out of the system, so suspect I’d indvertantly overfilled the system over time.
No massive increases in pressure once the thing got up to temp and no pressure loss when fully cooled down overnight.
Plus the PRV seems to be holding too.
RESULT!
Hows the pressure on your system holding up sadexpunk?

Hows the pressure on your system holding up sadexpunk?

We’re just checking that now.

your engineers very generous.. your filter on the flow immediately invalidates two major manufacturers warranties.. whats the point of cleaning the water after its passed through the boiler..

already changed a pressure vessel and a prv this morning dont have to do the prv but it saves coming back if its goosed..and only 18 quid.

thanks for the comments chaps.

thought it was sorted, not so sure now. daughter says pressure was only just above the red when she left this morning. its better, cos it had gone completely before, but id have hoped it wouldnt drop at all :-/ she’ll be reporting back tonight.
if it does, ill have to find out if any waters leaving the expansion pipe, as that will determine a boiler ‘over-pressure’ fault or a leak elsewhere wont it?

ill be having a word with the fitter tho, ask him why hes positioned the filter where he has. could there be crap getting stuck in the pipes constantly from now on then?

if your systems full of crap – in the rads and pipes…. and your putting in nice clean filtered water from the boiler…

guess where the craps going to end up before its captured by the filter.

im always amaized how much shit my magnaclean collects on an all new system with PEX pipes and delonghi rads filled with strong mix of fernox antifreeze(its an external boiler in teh country we get power cuts often) and inhibitor

b*ll*cks.

3 weeks after the engineer did whatever he did and fixed it, same thing has just started happening again.

what would this suggest to you experts out there? could it be the filter on the ‘flow side’? i know a few of you think its in the wrong place but ive also spoken to 2 other gas safe engineers who’ve said thats not cut and dried, and that its ‘boiler dependent’.

for whatever reason, the pressure is building until 3 bar, prv operates to dump water, pressure then drops to zero.
will have to ring Ideal again tomorrow……

What pressure is the system starting at?

Ideally 1 bar with everything cold, if the pressure is then reaching 3, either the expansion vessel is undersized (common on system boilers) or is knackered.

1 bar. and keeps being reset to 1 bar every time it dumps the water and drops to zero.

EDIT: if anything was undersized, then surely it shouldnt have been working for the last 3 weeks?

Good point about the vessel undersized, quite easy for an additional one to be added onto the pipe work.

How many radiators on the system ? Check the installation instructions of the boiler.

If the pressure gauge is is going from 1bar to 3bar with the heating on, that tells me it’s the pressure vessel either undersized / needs re-charging / or faulty.

Is the filling loop 100% turned off ?? It could be slowly filling the system.