Leak in central hea...
 

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Leak in central heating system

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I think I have a small leak as the upstairs towel rads are filling up with air and pressure is slowly falling. I know air rises but is it too presumptious to assume that this means the problem is somewhere upstairs?

Every now and then I also seem to need to bleed air from the magna filter which is downstairs, so maybe I and being to presumptious


 
Posted : 04/01/2023 12:39 am
 colp
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Normally you’d see an upstairs leak via a stain on the downstairs ceiling.
I’ve just fixed one where a tenant had knocked a panel pin into a rad pipe where it went through the downstairs floor, horrible tiny crawl space to work in.

Is it a combi boiler? See if there’s a dribble coming out of the pipe on the outside wall where the boiler is installed. Could be that the expansion vessel needs topping up. Easy job with a bike pump.


 
Posted : 04/01/2023 7:29 am
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Ive got a similar issue with air in the system and have had for years. I cant see any staining or wet pipes. Like you it must be coming from somewhere though. I think it gets sucked in from the air vent


 
Posted : 04/01/2023 8:07 am
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Ours apparently leaked (had to do a few combi pressure top ups per year) for a few years, no stains, nothing obvious atall, after the boiler went unviably wrong and a new boiler was fitted no leak (well had same pressure since March last year)so I’d check the boiler as well and see if its the problem ,


 
Posted : 04/01/2023 8:33 am
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Just had a leak fixed, we were topping up the boiler constantly, but only needed a small top up every time. The plumbers has asked about leaks/damp spots, which we hadn't seen, and had diagnosed the expansion vessel as the only alternative fault. Until we found the carpet in the under stairs cupboard was soaked, unnoticed as the carpet is rarely seen, as the cupboard is a dumping ground

Would mention a friend had loads of their downstairs ceiling fall in, no where near the leak, as the leak went unnoticed but happily filled the void


 
Posted : 04/01/2023 8:46 am
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Not a combi. The only pipe is the condensate one so would expect a flow from that. No staining but it’s not a fast decrease in pressure, 0.1 or so over the last few months.


 
Posted : 04/01/2023 8:49 am
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Try adding a dose of this https://www.screwfix.com/p/fernox-f4-central-heating-leak-sealer-500ml/766pp

Fixed my slow leak in a closed/ pressurised system, standard boiler.


 
Posted : 04/01/2023 9:04 am
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If you don't have enough corrosion inhibitor in the system, corrosion can give rise to gases in the radiators, which you have to bleed off, which drops the pressure! (Regarding the pressure drop, 0,1bar over a few months is hardly significant, mine varies that much just with the colder weather!)


 
Posted : 04/01/2023 9:11 am
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I have similar, have to bleed a significant amount of air out of the rad in our loft bathroom fairly frequently.  The Fernox leak sealer looks like a good option, how does one add it easily?


 
Posted : 04/01/2023 9:20 am
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I've had many small usually invisible leaks over the years. I just add the leak stop stuff linked to above. Bizarrely, now I've been messing about replacing bits it is rock solid. You'd expect it to be the other way round. But it may help that the temperature is now much lower in the system.

Easy job with a bike pump.

Not that easy. They are usually at eye level and the hose is not long enough on a bike track pump so it requires some gymnastics and upper body strength, in my case at least 🙂


 
Posted : 04/01/2023 11:42 am
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how does one add it easily?

Oh, I can help here.

- Choose a small rad
- Close the valves on each side
- Connect a hose to the drain spout at the lockshield valve (the one you can't undo with your hand) and/or place a large bowl under it
- Use bleed key to undo the drain valve
- Then undo the bleed valve and water will exit the radiator
- Once enough water has drained out to accommodate your leak sealer, stop the flow, then undo the stopper that the bleed valve is part of.
- Squirt peak sealer in, replace stopper thing and tighten bleed valve and drain valve.
- Undo both radiator valves to let water flow back in
- Then use the bleed valve to get rid of the air.

Easy and not disruptive at all.


 
Posted : 04/01/2023 11:48 am
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That said, your system should be under pressure so a leak would be letting water out, not air in...

It is possible that if the pressure is too low then on the uphil low pressure side of the pump air can be drawn in. It sounds like you have at least three floors which would exacerbate that risk.

If I put 1.5 bar in my 3 storey house system it seems to prevent bubbles.


 
Posted : 04/01/2023 11:51 am
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RE: adding the leak sealer, @mol's way is the way to do it with rad's only, but because you've got a Magna filter i'd use that.
Youtube will provide for the details but essentially the same process as for the radiator just a bit more convenient/less messy. I use this method to dose mine through the magna clean, if you have more inhibitor than available space in the filter body, fill it back up and cycle the heating for a few minutes to percolate the first dose through the system then repeat the process for the remainder.


 
Posted : 04/01/2023 12:46 pm
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The water is a bit orange. I added another few bottles of inhibitor a year or so ago I think though when I noticed this. Don’t seem to be forming hydrogen (which I assume would be the gas if corrosion were the problem) - or wasn’t last time I checked. Will try again.

The point on low pressure might be something though as I was running at 1 bar ish. It’s a system boiler so the pump is down stairs - higher than the downstairs rads but lower than upstairs ones.

However, Good point about being under pressure too so air entering shouldn’t be happening.

Feels like it must be one of the above though!


 
Posted : 04/01/2023 1:03 pm

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