No boiler pressure but no visible leaks - please help!

pug_lover

Hi Guys,

I realise this is a very old thread - but I thought I'd reactivate it as it explains our situation exactly!

The only difference is we've had no building works done at all - the boiler which used to work perfectly just started losing pressure. Now, 2 days after topping up to 1 bar, it's dropped back to 0 pressure.
The boiler is still working as we have hot water.
We aren't using central heating at the moment, but I wanted to get it sorted before Winter arrives!

I've been told there's a fluid that can be flushed through the system that will seal small leaks.
Has anyone had any experience of this?

I've also been told to wait til Winter is here to do this, as the Heating needs to stay on, once the fluid is in there.
Does that sound right?

I thought it might be a good thing to start with, before ripping up floorboards!

As an aside, I'm guessing it's not good to leave the boiler in this state, constantly topping it up?
What would happen if we did?
Last Winter the heating did still work, it was losing pressure much slower then, so we just topped it up every week.

Thanks!

squeekswhenwalking

Hi, your situation sounds a little different to the old post, the relatively small amount you are loosing will probably be something like small amounts of water leaking out the top of the radiator valves then evaporating (believe me I've done this many times) look for water stains on pipework, under rad valve cap etc. also check copper PRV pipe outside (the small pipe which should be turned back toward the wall) tape a plastic bag over the end of it and see if it fills over the day.
If you use the leak sealer I usually use Fernox F4 Express as its easy to install, particularly if you have an external filling loop (not built into boiler)

gas4you

As well as the above, pressurise your boiler to about 1.5Bar.

Isolate it from the heating system with the valves underneath it.

Leave it as long as possible. If the pressure drops it is a leak/fault on the boiler, if it doesn't, but then does when you open the isolating valves under it, it is a leak on the system somewhere.

pug_lover

Thanks so much sqeekswhenwalking and gas4you,

I admit that I don't think that it's under the floorboards but I've had two engineers come to the house and they insist that it must be and that it's not leaking from anywhere else.
There are very slight water/rust stains coming from the top of the radiators - which I have shown the engineers, who say that they are old stains and that's not where the leak is.

I'll tape a bag to the PRV pipe today to see what's happening there as well.

gas4you - I'm not sure how I isolate the boiler from the heating system (the heating system isn't on at the moment)
Would you mind telling me how to do that? I'm afraid I am an absolute amateur at boilers!
I've tried to attach a photo of our sustem for you but as a new user I don't seem to be able to.

It's a Protherm system - I can't find a model no. on it.
The filling loop is separate, underneath. There are 4 "taps" underneath. 3 red ones and a yellow one. The yellow one has the letters A and C on it, with an arrow indicating you rotate from A to C.

I've got another engineer coming on Monday to have a look at it - so it would be great if I was armed with some more information!

Thanks again!

Chunks

Hi there,

I had (reduced) pressure issues with my combi last spring relating to a leaking value on the bolier itself.

(Not being a plumber just thinking logically) if the rads haven't been on then that should rule out an issue in that 'loop' of the system. If my logic is right, we are talking about either the boiler itself or the hot water side.

Since you had the boiler installed (assuming you did) have you always had this experience? Is there any evidence under the boiler of water staining and/or dampness (that's how my problem was identified - slow leak since installation).

If you have any pictures you can post a link but you need to include a dummy character like www.moneysavingexpert[dot]com. The reader can simply cut and paste to a browser and substitute the [dot] for a .

cheers,

Chunks

pug_lover

Thanks Chunks,

We didn't have the boiler installed - it was here in the house when we moved in.

It worked perfectly for a year, then in January this year it just started losing pressure. So the central heating was on when it started losing pressure.

No building works, nothing changed in the system.
Although in January we did have that awful cold weather!

No evidence of any dampness either under the boiler or any of the rads.

I did put a link to the photo in that format, but an error message came up saying as I was a new forum member I couldn't post any links.

Any hints as to how I can isolate the boiler from the heating system would be appreciated, that sounds like a good start!

Thanks,

evoke

I had a small leak that went on for 5 months. No obvious signs of a leak but was eventually traced to a failed elbow joint in the pipework under the living room floorboards.

Unfortunately in a situation like this you will have to employ an experienced plumber who knows how to trace a leak. I was quoted prices of between £350 (no free payabale if leak wasn't found) to £850 for companies with specialist equipment (sonic, dyes, special cameras, etc). In the end I found a plumber who located the leak at the first floorboard he lifted! What a relief that was!

gas4you

The yellow one will be the gas isolating valve so don't touch that.

The 2 that need turning off are the valves that are connected to the 22mm (larger pipes) Bear in mind though, that sometimes if these valves haven't been touched for ages, they could leak when turned off.

pug_lover

Thanks gas4you, I might leave it to the experts on Monday then!

and yes, evoke, I hope he's an expert!

Thanks Guys!

greyhounds_galore

just bought a house and husband noticed water leaking out of the pipe from the back of the boiler that comes out of the wall. The wall has been badly stained by this. A plumber friend came round but at this point the leak had stopped from this pipe. He noticed that the pressure was very high on the boiler and said that the previous owners had kept this high to compensate for a leak somewhere. He couldn't find any signs of a leak from the radiators or boiler and is convinced it is under the ground. He said all you cane do is pull up floorboards and see how deep the crawl space is to investigate. The pressure now keeps dropping and the system switches itself off and this can happen within an hour of turning the little blue nozzle to fill up the system - so he thinks there could be numerous leaks but probably quite small ones - he's obviously not really interested in crawling around underneath the house and I am sure that this would be an expensive job to call out another plumber - we move into the house in 2 weeks so eed to sort this out - especially as we want to go on a water meter and my friend says we're losing alot of water this way so my question is: another person mentioned a sealer that can be flushed through the system and someone else mentioned using Fernox F4 Express but only if the external filling loop wasn't in the boiler - I'm guessing ours is if that's the little blue nozzle I've been turning! so what else can we use to try and avoid pulling up floorboards? Any answers much appreciated !