Hi,

I have a Glowworm Swift Flow 100 Combi Boiler. When I recently started using the central heating system again after the summer, I bled all the radiators and topped up the system from the filling loop.

A couple of weeks ago I noticed that when it is in its 'rest state' and cool the pressure had dropped below the red marker on the pressure guage, so I checked the radiators for leaks and topped up the system again. The system seemed to lose pressure again, but I have now also noticed that when the central heating turns on the pressure gradually increases by 1-2 bar.

I have been round the house several times checking for leaks (radiator bleed valves, pipe joints etc.) and I can't find any sign of leakage.

Is this something I should be worried about?

Grateful for any advice.....

It looks like you have a leak somewhere!

Don't worry about the pressure rising when the heating is on this is quite normal!

Hinton heating may be able to advise better but you could try adding some leak stopper-

http://www.screwfix.com/app/sfd/cat/pro ... 9&id=45902

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DIY | Donnas dream house

It should ONLY rise by a very small amount. When system is hot, where does the pressure rise to?

if its anyway near 3bar, then chances are that the pressure releif is letting the water "leak" out.

once water cools, it'll then drop to a low level!

This is caused by a faulty expansion behind boiler.

How good are you at draining sytems & pumping up car tyres?

Thanks for the quick replies!

The pressure rises to a little over 2.5 bar when the system gets hot, so I guess it could well be escaping through the relief valve. Now it hasn't been running for an hour or so, the pressure is sitting at 0.7 bar. It does drop even lower though.

What is a 'faulty expansion behind the boiler'?

I'm pretty handy, changed radiators (drained the system to do that) plumbed in a new bathroom/kitchen etc. Is that good enough to have a go?!

Cheers[/quote]

pressure vessel.

This is a large red cylinder behind the boiler, you probally need to look over the top & down the back.

locate the tyre valve.

press the middle, one of 3 things will happen...

1 - you get a rush of air, as if pressed valve on an inflated car tyre

2 - you get nothing at all, as if pressed valve on a completly falt tyre

3 - you get water out.

for both 1 & 2 you need to do the same...

- drain system, no need to open radiator bleeds.
- leave hose connected & drain off open
- attach pump to the air valve on expansion vessel
- pump up to 1bar
- remove pump, replace dust cap
- repressurise system with water to 1.3bar

for 3 you have a damaged expansion vessel, and it'll need replacing (usually boiler off wall) or a secondary one fitted elsewhere on the system.

when the pressure is at its highest, have you checked the safety pipe outlet outside?

I had a system loosing pressure, the leak sealer helped, but it ended up in taking up all the floors to reveal a leaking pushfit connecter.

They hadn't used an insert, and didn't push the pipe fully home, so it didnt seal on o ring

But don't rely on the indicator on the pump; get a better tyre pressure gage for that. The pump ones are notoriously wrong!

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Jaeger.
Senior Member doesn't mean I'm OLD!

darrenc wrote:

I dont think its a stupid question but does show a lack of understanding of how paint works and reasons for certain applications, now dont jump down my throat Jaegar i'm not being funny its just a classic case in point of a well educated professionally trained painter against a general tradesman.

Thanks for the advice :grin:

I'll have a go and let you know how I get on.

Cheers!

:grin:

Hinton Heating,

Just wanted to say a big thank you! I left tackling the boiler until after the Christmas holiday (didn't want any disasters just before!), and followed your advice and instructions to great effect.

The pressure vessel was indeed depressurised (a small 'phhtt' was all that was left inside), but no water from the valve. Now it is pumped up again, and the system re-pressurised, the pressure guage is very stable.

If I could add one further piece of advice to anyone else with the same problem - wearing a thick wooly hat to protect your head against the stippling on the kitchen cieling while you look over the top and down the back of the boiler also helps!!! I'm still picking bits out of my head

Cheers!

i have a swiftflow 80E and had the same fault. Hinton helped me too

it truly is one of the worst boilers I have ever come across

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Decking

yes, its certainly a bad one!