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Central heating boiler losing pressure, what to do?

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Ribenapigeon
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PostPosted: 17:33 - 12 May 2017    Post subject: Central heating boiler losing pressure, what to do? Reply with quote

My combi boiler occasionally loses pressure so i just open the top up valve and boost it back up. Its doing every other day at the moment though. I know when the boiler gets serviced the servicing dude does something with a big bicycle pump to the expansion chamber and i think this fixes the problem but i dont want to have the boiler serviced until july (cssh flow blahh blah). Is this something i could do myself? Im guessing its not a gas safety issue.

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grr666
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PostPosted: 17:41 - 12 May 2017    Post subject: Reply with quote

Have you tried boiling your head?
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arry
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PostPosted: 17:50 - 12 May 2017    Post subject: Reply with quote

System is probably leaking somewhere. Check rads for any obvious signs. Either that or common places for them to go are the flow switch or gas valve (ie it'll be dripping water out under the boiler : stick a tray under it).
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Rogerborg
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PostPosted: 18:11 - 12 May 2017    Post subject: Reply with quote

The expansion chamber has a standard Schrader valve, you can repressure it with a bicycle pump.

Cap off, press the stem. If water comes out, that's your problem, the membrane has gone. If it's dry and up to pressure (~1.5 bar) then you've possibly got a leak. It could be somewhere you can't see.

I've had great success with dumping leak stop goo in. It... stopped a leak somewhere on the system. Can't really say fairer than that.

If you have a filter on the system you should be able to get it in there, or shut off a radiator, remove the bleed valve stem, and see if you can get in that way with a syringe - ask one of your customers to supply a big one.

It wouldn't hurt to put more inhibitor in while you're doing that.
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Freddyfruitba...
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PostPosted: 18:33 - 12 May 2017    Post subject: Reply with quote

Rogerborg wrote:
If you have a filter on the system you should be able to get it in there, or shut off a radiator, remove the bleed valve stem

The easiest way (ie, no need to drain radiators etc) is via a towel rail if you have one, with a bleed valve at the top, pointing skyward... depressurise the system, unscrew the bleed valve and pour in the gunk
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Ste
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PostPosted: 18:54 - 12 May 2017    Post subject: Reply with quote

You should see a debt advisor about those money flow problems. Thumbs Up

someone wrote:
there's a whole range of reasons people get into debt some of them quite bizarre. Take for instance a common situation I encounter where clients just dont realise how poor they actually are. This has several effects. They spend more than their income, they feel that they should be able to have material luxuries (subscription telly, iPhone etc) and they act impulsively. Ive lost count of the number of times ive had to spell out to people how poor they really are, actually having to say to them "listen...you...are...POOR". Why some people have such difficulty coming to terms with this is I believe because poverty has had such a stigma attached to it, people often borrow in order to foster the delusion that they are doing better in society than they actually are.

Poor basic education levels and growing up in households where there are no positive roll models where everyone does poorly increases the likelihood a person makes poor decisions. The idea all these people just get a loan from a loan company with no intention of paying it off is rubbish as well, just another fantasy of those who want to find another reason to look the other way as society becomes more divided. A lot of the time with clients who have standing debts im having to advise them how to contact the loan company and have the debt reduced and payments reduced to something that fits with their income.

The debt advisor should also be able to put you in touch with the appropriate services for getting your hovel fixed and explain to you why if you need to ask if fiddling around with a combi boiler is a gas safety issue then it's not something you should be doing. Mr. Green
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Ribenapigeon
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PostPosted: 19:53 - 12 May 2017    Post subject: Reply with quote

Ive topped up the pressure and im going to see if it drops without the heating running then do more investigation. Ive had a good look round and no sign of leaks. Ill take a look at the expansion tank tomorrow and see what the pressure is there and if it has a leaky nipple.
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Dave500
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PostPosted: 19:53 - 12 May 2017    Post subject: Reply with quote

If the engineer is using a bike pump to re charge the expansion chamber its probably on it way out and could be leaking slightly. If its towards the front of the boiler get a quote. In the mean time look for leaks on pipework or on radiator valves.
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Bikeless
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PostPosted: 20:43 - 12 May 2017    Post subject: Reply with quote

Bladder is probably knackered
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Rogerborg
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PostPosted: 20:46 - 12 May 2017    Post subject: Reply with quote

No Blade wrote:
Bladder is probably knackered

Kegel exercises?
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mudcow007
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PostPosted: 16:14 - 15 May 2017    Post subject: Reply with quote

auto air vent sprung an not returned due to some crap maybe?

look for any dribbles of water in/ around the boiler.

Had it on mine, thing a valve was about £8

My boiler is ancient though yo - Worcester 24i
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angryjonny
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PostPosted: 16:26 - 15 May 2017    Post subject: Reply with quote

Reasons mine has lost pressure:

1. Fubar'd expansion vessel
2. Fubar'd heat exchanger

1 is a quick and fairly straightforward job for a plumber. 2 was a complete boiler rebuild that would have run well into 4-figures were it not for my maintenance contract.
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ScaredyCat
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PostPosted: 16:30 - 15 May 2017    Post subject: Reply with quote

mudcow007 wrote:
My boiler is ancient though yo - Worcester 24i


Pfft, we have a Potterton Statesman, it's 1 million years old.
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Ribenapigeon
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PostPosted: 18:41 - 15 May 2017    Post subject: Reply with quote

Found the boiler was venting water out the pressure relief valve. Worrying as it suggests the system is bunged up somehow.
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angryjonny
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PostPosted: 19:08 - 15 May 2017    Post subject: Reply with quote

Tap the expansion vessels. Do they go "ting"? You're good. If they go "thunk", you're less good.

The expansion vessels are to allow compressible air to absorb the expansion and contraction of the system/water as it heats and cools. Water is not compressible so if there isn't an airspace, as a last resort it'll vent through a safety valve of some sort. Sounds like that's what's happening.

If it's slow leak, when the pressure drops again, try the bicycle pump approach. That'll get some air into the expansion vessel. If you use the standard filling loop you're just replacing the air with water.

Temptation is to bleed your radiators. That'll make it worse as you're just removing more air from the system.
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Ribenapigeon
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PostPosted: 19:49 - 15 May 2017    Post subject: Reply with quote

Water pissed out of the expansion vessel when I actuated the valve. So guessing its new expansion vessel needed.
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stinkwheel
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PostPosted: 19:55 - 15 May 2017    Post subject: Reply with quote

Ribenapigeon wrote:
Water pissed out of the expansion vessel when I actuated the valve. So guessing its new expansion vessel needed.


Yes. Should only be stinky air in there meaning the bladderr has gone.

It also means it'll go over pressure and piss water out when it heats up.
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Ribenapigeon
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PostPosted: 20:09 - 15 May 2017    Post subject: Reply with quote

Its a £70 part so fuck it I'll call the engineer tomorrow and get it fixed. Need my crappy old living room gas fire disconnected anyway so get that done as well.
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stinkwheel
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PostPosted: 20:21 - 15 May 2017    Post subject: Reply with quote

I fitted my own. It was one nut with an o-ring in for mine. Took longer to drain the system than to fit the pressure vessel.
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arry
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PostPosted: 20:45 - 15 May 2017    Post subject: Reply with quote

Tend to find once they get to a stage where bits need swapping you end up laying out money after money. Best build a slush fund and know when to call it quits on the current one.
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Ribenapigeon
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PostPosted: 17:31 - 16 May 2017    Post subject: Reply with quote

What i dont understand is the expansion vessel acts as a kind of air spring, right? So why have the air in one side of a diaphragm? Why not just have the vessel above the highest point in the system and charged with a given amount of air and if air gassing ing out if the system builds up just have a simple vent actuated by the level of water in the vessel to maintain the right volume of air?
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Al
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PostPosted: 18:30 - 16 May 2017    Post subject: Reply with quote

The expansion vessel is often inside the boiler so if it had to be fitted at a high point you'd be limited on where the boiler could be installed.
The air side is also normally set at a slightly lower pressure than the heating water side which wouldn't be possible without the rubber diaphragm.
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Rogerborg
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PostPosted: 19:32 - 16 May 2017    Post subject: Reply with quote

Why a combi system needs to be sealed rather than the much more tolerant feed-and-expansion system does actually puzzle me. I've never seen a simple explanation for why.

I've read articles suggesting that sealed combi systems have become the default because:

Arrow They're easier to fit.
Arrow They generate much more repeat business for plumbers.

My current combi system is 7 years old and has had three callouts this year, all down to crud in various small-tolerance components, the last being the narrow diameter hose to the expansion vessel. The wrench-monkey was very familiar with the problem.

This despite having a magnetic filter that I clean out regularly, while re-dosing with inhibitor. A process that is much easier with a F/E tank.

The wrench-monkeys have covered this up each time as "component failure" because they know fine well that silt is a specific exclusion on these plans, and they don't want the payment for their services being argued. It'll catch up on me soon though, and the system will be "beyond economic repair" at closer to 5 years than 10.

At which point I'll be asking about options for re-plumbing the feed/expansion tank in the attic, putting a hot water tank back in (should never have let them take it away) and fitting a solar or ground source heating loop for it.
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angryjonny
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PostPosted: 20:54 - 16 May 2017    Post subject: Reply with quote

We have a pressurised system with tank and 2x pressure vessels. 2 heating loops (bedrooms and everywhere else) and hot water, so 3 motorised valves.

In 36 months from new we lost both pressure vessels, one motorised valve and the heat exchanger in the boiler.

tl;dr they're all made of cheese
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MCN
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PostPosted: 23:08 - 17 May 2017    Post subject: Reply with quote

Pressurised systems will permit higher boiler temperatures.

And stuff...
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