Tracking down a central heating system leak

espresso

odgeuk wrote: »

I'm having a similar problem with a 6yr old Baxi Combi. The pressure will drop from 1 bar to almost zero in 4-5 days. I've been topping it up for months.

It seemed to become this bad shortly after I had an engineer out to repair a filling loop which had over-pressurised the boiler due to a faulty valve. Prior to that I had some recollection that I needed to to it up just maybe every 4-5 weeks.

Anyway, the engineer who repaired the filling loop, cleaned and resat the Pressure Release Valve and said to keep an eye on it. I didn't see any water or dampness from the PVR after that but the boiler still continued to lose pressure.

Many months later, I had a new diverter valve fitted, and the secondary heat exchanger cleaned in an Acid bath, to fix a problem with Hot water entering the Heating System (and running intermittent cold through the taps). At the same time I asked the engineer to replace the PVR to see if it fixed the pressure issue. He also checked and pumped up the expansion vessel and stated that as water wasn't coming out of the valve of the Expansion vessel, that the pressure problems were unlikley to be related to a faulty Expansion vessel. (he also said that if it was the Expansion vessel, then eventually, after topping up as much as I had been, it would overpressurise as the water would have nowhere else to go).

Anyway, so here I am, with either a faulty boiler, or a leak under the floor somewhere in my central heating pipes.

I was very concerned to hear that continuous topping up leads to sludge in the system??! I have an inhibitor inline with the water supply to the boiler which I'm told should work for the lifetime of the boiler? The last thing I can afford right now is a Powerflush.....

Can you elaborate on this "inhibitor inline with the water supply to the boiler"? After continuously topping your system up for so long, I doubt if you have any system inhibitor chemicals left.

Myser wrote: »

Repeated topping up and thus dilution of the concentration of inhibitor already in the system, reduces its effect and eventually can lead to sludge build-up if you do not top up the inhibitor as well.

odgeuk - in your case, as the inhibitor is added inline with the water supply, this shouldn't be a problem. You just have to check that the inhibitor reservoir doesn't get empty!

I believe that this is incorrect. How could chemical inhibitor be added inline with the water supply to a combi boiler? I have never seen any such device.

odgeuk

espresso wrote: »

Can you elaborate on this "inhibitor inline with the water supply to the boiler"? After continuously topping your system up for so long, I doubt if you have any system inhibitor chemicals left.

Yes, I have mixed up my terminology. I was referring to the canister style device inline with the water supply, which I guess prevents scaling from the Cold water supply? An Inhibitor is presumably a chemical something which prevents the water in your heating system rusting your radiators? In which case, I daresay I am in desperate need of a powerflush.

Canucklehead

Hi...a Combimate. Fit one of these available soon or its predecessor.

HTH

Canucklehead

beansgran

We have the same problem with our Worcester. We have the BG Homecare contract and the engineer comes regularly. He pumps up the expansion chamber (or whatever - I'm not a tekky) and says it's quite safe and just to top up if necessary. I'm attracted to the idea of an additive which can seal the sysem if pumped in through a rad - has anyone used this ? The way things are at the moment we need to top up every couple of days and that can't be right !

Myser

beansgran wrote: »

We have the same problem with our Worcester. We have the BG Homecare contract and the engineer comes regularly. He pumps up the expansion chamber (or whatever - I'm not a tekky) and says it's quite safe and just to top up if necessary. I'm attracted to the idea of an additive which can seal the sysem if pumped in through a rad - has anyone used this ? The way things are at the moment we need to top up every couple of days and that can't be right !

Have you checked the overflow pipe? Is the PRV (Pressure Relief Valve) leaking?

Regular re-pressurising of the expansion vessel isn't a good sign.

CH coagulant liquids aren't receommended for newer boilers by certain manufacturers as it can also clog up parts such as the heat exchanger.

unclebulgaria

Canucklehead made a good point. Isolating the boiler from the heating system is as good a place as any to start. A few other things you could look out for are; 15mm pipe exiting through the wall under the boiler to an outside position, possibly returning back to face the wall or going down to floor level, dripping? Multiple radiator valves weeping showing green stains running down the pipes?
Little leaks that look insignificant when multiplied can knock down system pressure quite quickly.
As for expansion vessel pressure, did the RGI not check for this as it causes the CH system pressure to rise during firing and a false pressure reading? If you watch the boilers pressure gauge during firing it will rise quite quickly, possibly over the 3 bar mark, if the pressure rises too high the relief valve operates and the CH loses pressure, you then fill it back up and its never correct.
Have a look around the property, if you haven't already, and see if their are any orange stains appearing on your ceilings. Signs of a leak?

curly35

I have a similar problem, I have to keep topping up my boiler pressure, often I come home to a freezing cold house because the heating hasn't come. Recently used my boiler cover to "fix" the pressure and a leaky radiator, but two days later, pressure dropped again. Radiator that was leaking is no longer. But now my shower is not working either - pressure has completely gone - it's a shower direct from taps on the bath. Any advice?

southcoastrgi

Myser wrote: »

odgeuk - in your case, as the inhibitor is added inline with the water supply, this shouldn't be a problem. You just have to check that the inhibitor reservoir doesn't get empty!

i think they have got it wrong, i think what they mean is an in-line scale inhibitor on the cold supply to the boiler, this is totally diff to putting inhibitor into the central heating system.

A couple of tips for anyone with the same prob, locate the small pipe on the outside wall from your boiler this is the "blow off" pipe from the pressure relief valve inside the boiler, get a small clear bag (something like a freezer bag) put it over the pipe tape round the top of the bag (so no water can get in) & see if you get water in there if you do it's a faulty prv, expansion vessels sometimes can lose pressure over a period of time eg a slow punture on your car, if it req re-pressurising on a reg basis time for a new one, hope this helps.

suzy333

Hello, please does anyone have advice for me, we have a new boiler 2/3months and have to top it up every week , the plumber has been out a few times ,we did find a leak on one of the radiaters, but has now been tightened, he now says it must be a leak under the floor, and our downstairs is concrete floor, he is coming this morning, and I think to dig up a corner, but surely it could be anywhere, any ideas ? also I was wondering would it be possible to just put new pipes in , and would the leak stop , and how much do you think this would cost ? thank you for any advice ,Im passed myself with worry, Suzy

southcoastrgi

suzy333 wrote: »

Hello, please does anyone have advice for me, we have a new boiler 2/3months and have to top it up every week , the plumber has been out a few times ,we did find a leak on one of the radiaters, but has now been tightened, he now says it must be a leak under the floor, and our downstairs is concrete floor, he is coming this morning, and I think to dig up a corner, but surely it could be anywhere, any ideas ? also I was wondering would it be possible to just put new pipes in , and would the leak stop , and how much do you think this would cost ? thank you for any advice ,Im passed myself with worry, Suzy

if it was a leak in the floor you would normally see some evidence of this if it's been doing it for a while, however if you increase the pressure in the heating system ie changing from a open vented system (small top up tank in the roof) to a system boiler or combi then yes if your pipework is weak then leaks can occur, if it's a leak in your solid floor then i wouldn't even bother to trace it as it's likely to start leaking somewhere else, the best solution is to re-route the pipework to every down stairs rad by dropping pipes from above & doing away with the existing buried pipework, not a cheap job unfortunately.