Has my central heating got a big leak?

Hello uk.d-i-y world.

Yesterday, I thought I'd put the heating on... it being June and all.

There was a bit of gurgling from a radiator that usually gurgles, so I bled it and put a bit more water into the system - by turning a thing that is a bit like a washing machine tap. System came on and worked for a bit then it stopped working. I was puzzled but left it to this morning to have a closer look.

The boiler is a Worcester Bosch Greenstar CDi that was fitted last November. The plumbing (radiators etc.) are of an older (~90s) vintage.

The hot water is working fine.

This morning, before switching on, the system pressure gauge showed 0, and the display 72 (I guess degrees). I'm not sure what these numbers would normally be before switching on.

After I switched it on, the temperature quickly rose past 99 and then u1.. u9 (which I guess is not right). The radiators didn't come on. I bled a few and a little bit of air and distant gurgling occurred, but no actual water.

I'm about to call our service guy, but just to get an idea... Is this likely to be the boiler? or, more horribly, a pipework issue?

(The house is a bungalow, and I'm a bit worried that the pipework could be dumping water without us knowing).

Thanks for any ideas.

Bob.

Reply to
WeeBob
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I'm guess that you have a pressurized system. So if you did have a leak, there'll be no water left to fill the radiators when you try to bleed them.

Depending on how much you believe you know, you can either wait for the engineer or try repressurising the system gently whilst you or a spouse/friend check around the bungalow listening for leaking water. If you can't find any, bleed, repressure, bleed until the system seems full and try the heating - you'll probably have to bleed/refill again as there'll be air moved around once the heating starts up. Then watch the pressure again and see if it drops indicating a leak.

If the pipes are buried then feel for wet bits of carpet etc. and don't forget any unused rooms, garage (if there are pipes in there) etc.

Good luck! Paul DS.

Reply to
Paul D Smith

Is your expansion vessel still pressurised ? I had a problem a few months ago with our CH - kept on losing pressure by blowing water out of the safety valve. Turned out the expansion vessel had lost some air. After some acrobatics on a chair, I managed to connect a bicycle pump to it, and repressurise. Been fine since.

Can't speak for your model, but expansion vessel on mine was right at the back of the boiler and a pig to reach :(. If it needs replacing, most engineers simply fit one elsewhere !

Reply to
Jethro_uk

You shouldn't have gurgling radiators or need to regularly bleed "air" from the system. As you say this is a recent install did the person who replaced the boiler add inhibitor to the system when they refilled it? "Air" is in quotes as it maybe hydrogen, the result of corrosion in the system due to lack of inhibitor.

So it's lost pressure, this does half indicate a leak but it might not be in the pipe work. A common culprit is a lump of crud in the pressure relief valve or a failed expansion vessel (pressure shoots up when the system fires, (opening relief valve allowing crud into it...), then when the system cools the pressure drops right back.

Reply to
Dave Liquorice

Never underestimate the amount of water a ceiling can hold before breaking through! I reckon mine had been leaking for some months - pressure to zero after a week or two - before I finally got round to having a systematic look.

Fixed a pipe under the FF floorboards and replaced all rad valves while it was drained. Figured it was a false effort/economy not to do the valves, especially as a couple showed signs of weeping.

Rob

Reply to
Rob

Hm... After checking stuff further, the hot water is not working. I guess there was just enough left in the tank to have a shower this morning.

Reply to
WeeBob

The pressure should read about 1.0 when the system is cold, so if the pressure dropped to 0 then the boiler would (should!) refuse to fire, although it sounds like it may have fired anyway and then tripped an overheat sensor as you said "After I switched it on, the temperature quickly rose past 99 and then u1.. u9" so you may need to reset something once you have taken the pressure back up to 1.0.

I suggest you do the following...

  1. Turn off the hot water, so the boiler isn't trying to heat the hot water cylinder.
  2. Turn down your room stat so it is not trying to heat the radiators
  3. make sure your bleed valves are all closed on the radiators
  4. try letting more water into the system with the valve that looks a bit like a washing machine tap, and watch the display on the front of the boiler, you should see it rise from 0 - Stop when you get to 0.5
  5. Hunt around the house to see if anything is leaking, including outside at the back of the boiler, where you should find a metal (copper) pipe that should either end part way down the wall, or go to the ground, but not go to a drain
5 If there any any leaks, top it up until it is at 1.0 and check again.
  1. If you cant see any leaks, leave it like this for 15 minutes or so, and see if the pressure drops.
7 If not, go round and bleed your radiators, if there is a lot of air in them, you will need to go back and fill the system again every so often, as bleeding the air will result in a loss of pressure.
  1. Once they are all bled, and you have topped it back up to 1.0 fire up the heating and see how it goes.

Let us know if you run into a problem!

Reply to
Toby

All good stuff, but if the expansion vessel is shot - or or has just lost its pressure - no 'leaks' will be found until the system gets hot again, whereupon the pressure relief valve will open and will discharge water outside.

So, to the OP . . . When you get to the end of the above list, if you haven't found any leaks (as seems likely), keep a careful eye on the pressure gauge as the system heats up - and look for water flowing outside, wherever the outlet from the PRV discharges - particularly if the pressure has got above 3 bar. If this *is* happening, report back - and we'll tell you in a bit more detail how to fix your expansion vessel. Oh, and if the boiler still refuses to fire when you've restored the pressure to 1 bar, look for an over=temperature trip which needs to be manually reset.

Reply to
Roger Mills

Its not right (typically it would show around 1 bar on a cold system and more on a hot one), but may not be a leak...

It could also be a classic symptom of inadequate expansion space. See the sealed system FAQ:

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Reply to
John Rumm

Thanks for that really detailed list.

Briefly, switched it all off. Filled it all up. Waited for

Reply to
WeeBob

To reiterate what I just posted to Toby, I switched it all off. Filled it up, and after 10minutes the pressure was back at 0. Tried it a couple of times with the same result.

I have to conclude now that I've got a leak.

Diagnosing where about is going to be "interesting" and probably expensive. There is nothing visible above the floor surface, so I guess it's underneath someplace.

Ah well.

Sincere thanks to everyone for the very useful posts. What a great newsgroup!

Reply to
WeeBob

To rule out the boiler, close the flow and return isolators on the boiler and pressurise to around 1.5 bar, if it drops, the leak lies within the boiler. If it is a condensing boiler the water can also be lost through the condensate pipe.

Reply to
gremlin_95

As Dave said, I would check the "PRV" outlet, normally a copper pipe leading outside, should be run down to the ground or just turned into the wall. If water is coming out of this then it could be the PRV (Pressure relief valve) that has failed, or maybe it has some crud in it that is making it pass water (I have had this before, and manually exercising it sorted it out), also check the condensate pipe, this should come out the boiler (usually a plastic pipe, sometimes ribbed flexible, like a washing machine's drain pipe) and lead to a drain somewhere, so you will need to find the end of that and watch it to see if it is dripping, it shouldn't drip at all when the boiler is off.

On the central heating pipes (should be 22mm) you usually have some isolation valves you can turn off, if you turn these off and then pressurise the boiler again, that will tell you if the water is escaping out the boiler, or somewhere else (so if the pressure still drops, then the problem is in the boiler, or they are passing water when off)

Do you have a copper hot water cylinder and then hot taps supped at low pressure (that you could easily stop with your thumb)? If so, you may have a leaking coil in the hot water cylinder which would mean water from the boiler's circuit you pressurised is getting lost in the lower pressure cylinder, so you wont see that anywhere - to test that you need to check the level in your cold water tank in the loft, then pressurise the boiler (probably a few times, depending how much water it takes to get to 1.0 bar), and see if the level rises in the tank (obviously don't run any taps during this test), if so, that is the problem.

Reply to
Toby

How much water did you have to put in to get from zero to 1 bar? I would expect it to take several litres. If it only takes a small amount, it indicates there's very little expansion capacity - pointing to a problem with the expansion vessel. In that case, only a small amount has to disappear somewhere else for the pressure to fail again.

Similarly, if it takes several litres, that several litres has to be going somewhere when the pressure drops. Is it a combi boiler, or do you have a stored hot water cylinder?

Reply to
Roger Mills

Yup, a good test. Another check is to tie a plastic bag over the PRV pipe with a rubber band, and see if it collects any water (it should not normally)

Reply to
John Rumm

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