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ice cold

Hi
I'm new to the forum so apologies if I've posted incorrectly. (if I have please let me Know.)

My combi boiler has started losing pressure. I noticed last night when I turned on the hot water tap, but the boiler didn't light. I filled the boiler via the filling loop to about 1 bar, but when I got home from work this afternoon I checked the boiler and the pressure had dropped to about 0.5 bar.
The boiler's a Main combi 24 HE, about 18 months old.

Before I call out a service engineer can anyone suggest a likely cause? I've checked the boiler, radiators and exposed pipework and can't find any sign of leaks.

If the best advice is to call out the engineer, is it okay to leave it until the new year, and just keep filling up the boiler?

Final question -the user guide for the boiler says to fill the boiler between 0.5 and 1 bar. I've read some threads in the forum which suggest up to 1.5 to 2 bar. What's best?

any advice appreciated.
 
have you any pipework in solid floors etc ?
check the prv pipework that exits the external wall for leaks.
fill the system to about 1-1.5 bar
 
Hello there, I had same problem couple of weeks back with a baxi. I changed the prv, problem solved. You should be able to check to see if its leaking by inspecting the external safety pipe, it doesn't have to be much of a leak to be a problem It might just be a drip.
 
Thanks for suggestions re: prv's. I've checked the prv outlet pipe & it's got a small leak - about 1 drip every 35 seconds while the boiler is running. I haven't checked it yet when the boiler's off.Is this enough to lose pressure overnight? I filled it to 1.5 bar yesterday evening, got home today it was down to 0.9
As for the rest of the pipework it runs down a cavity from the attic to the first floor, branches off to bathroom & bedrooms, continues down to the cellar then back up to kitchen & living room. Most of the pipework is plastic (or PVC ?) so I don't think there are any hidden joints, and there's no sign of moisture on any pipework.
 
There's 2 possible problems here.

1. PRV is faulty or has some muck on the seat, If there is muck on the seat you may be able to clear it by operating it, if the seat is damaged you'll have to get it changed.

2. expansion vessel has lost it's charge pressure. You can tell this by looking at the pressure gauge when the system is running. There should normally be 1/4 - 1/2 bar rise as the system heats up, if it rises dramatically there is a problem with the expansion vessel. It either needs recharging or the diaphragm may have failed.

Mike
 
Thanks for the suggestions Mike. The pressure seems fine at the moment - 1.0 cold, 1.5 with the boiler running, so the PRV seems the likely problem.

Senior moment! Then PRV drip mentioned in my previous post is actually from the condensate drain. (plumbing's not one of my strong points especially not gas boilers)

Is the PRV easy to check or should it be done by a Corgi plumber? - bear in mind my comment on the previous line!
If it does need replacing any idea of an approximate cost? Do Corgi plumbers usually charge a call-out fee, or just charge for the work done?
 
Ice Cold - did you get a reply about this? I have the same make and mdoel of boiler and the same problem - my boiler takes a week from topup to 2.5 bar to be drained down and cut off from working automatically (havent found any leaks anywhere) - the boiler is only about 18 months old also and a few months ago I already had to replace the air pressure switch - am considering taking out an extended warrenty and trying to get it fixed on that

James T
 
The sticker on the unit itself says the pressure must be between 1 bar and 2.5 - most of the time I top it up to just under the 2.5 mark though so that I wont need to fill up so soon

James T
 
if you top it up to 2.5 bar you'll have to be careful as the water expands if it reachs 3 bar it will activate the prv.

if it takes a week to drop it may not always be a visible leak.
 
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Yeah - I always make sure that I power up the boiler straight after toping it up - if it goes over the 2.5 mark I release some water from a rad in the house.

Thats the prob I have - cant see any leaks anywhere in the house or on the outside overflow pipe - before the fitting of the boiler I had an old tank system, got that taken out and the boiler moved to the loft and got the rad valves all changed (unfortunately my downstairs is a concrete base house but havent had any damp patches/mould or any other telltale signs of a water leake) and ever since the system was about a year old ive been having to top up water more frequently.

JamesT
 
>ive been having to top up water more frequently & concrete floors

don't sound good.

see this many times when a gravity system is changed to a pressurised system and the pipework don't like it.

you can have a weak pipe/joint for yrs on gravity but soon as converted to pressurised it gives in.
 
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Damn - old system was in for about 25 years before this new boiler was put in. Are there any ways to make sure there are no leaks/bad joints in old pipe work apart from the obvious of ripping the whole house apart/ taking up all concrete floors etc? I take it the cost to finally sort this would be very high to fix

JamesT
 
I'm no expert, but what about using gate valves (low resistance to flow) or similar to divide your system into zones; say upstairs & downstairs. Then shut a zone off for a few days or so & see if pressure drop keeps happening. If there is one leak rather than small leaks all over you could chase down it's rough position & limit how much floor etc you rip up. Obviously the gate valves would be installed in easy positions, such as the flow & return pipes going upstairs on surface of plaster.
 
It's not easy to check the potential leaks but you could eventually find some discreet places to cut off the under concrete section of pipework to mess a bit with them, for instance fit two valves at the edges of the pipes, then screw a pressure gauge on one of them, then connect a mains to the second, fill the section with water, close the valve mains is connected to and watch the gauge if there is any loose or not. Bleed the rads and close their valves. You could eventually connect the gauge to a rad's valve, but it's harder to bleed the section. This solution would damage uncovered pipework aesthetics, cause you would have to connect the pipes again. Also you would have to be sure each section of under concrete pipework is isolated, the valves are closed etc. Not perfect, but always _some_ way to check for invisible leaks.
 
Ice Cold - did you get a reply about this?

James T

After a couple of days of the pressure dropping to 0 and topping it up the problem seems to have gone away.

I'm guessing that as Mike said, there was some dirt on the PRV and it must have cleared itself. Don't know if this is a likely explanation, but I've checked the boiler and there hasn't been a drop in pressure since.

Thanks to all for advice and suggestions anyway.
 
If Your PRV is ok and you have no leaks on the system test the pressure vessel on the boiler it might have lost it's charge.!!
 
If Your PRV is ok and you have no leaks on the system test the pressure vessel on the boiler it might have lost it's charge.!!
I have a similar problem as descibed here ( posted as a separate thread) and will try the prv fix first - but to what pressure do you recharge the expansion vessel. My boiler = Ferroli F30 COMBI.
 
Hi Guys,

I have an Ariston Micro GENUS HE bolier (24months old) ... it seems to be losing pressure around 0.5bar every 6hours or so ....

iv been loking around for possible leaks without success ...

However there's a drip at the water Mains internal stopcock ... would that be a possible cause?
 
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