Tracking down a central heating system leak

technurse

I had this problem, pressure would drop from 1.5 to .5 bar in 2 days. Couldn't find a leak anywhere and feared all the floorboards coming up. Then I thought the only part of an otherwise closed system is the over-pressure release valve that vents to outside. I put a pan under the pipe and sure enough, it slowly started to fill with water! The release valve is situated inside the boiler, it is easy to see from underneath and has a red plastic cover on mine. The valve has a manual activation ability by pulling the central brass lug out using a screwdriver. I manually vented a couple of times and let the valve flick back into place, hoping it would bed-down better and voila! No more water from the vent pipe and pressure keeping up! Hope others find this simple solution works for them.

hsd_fan

I'm glad I found this thread!

I'd bled the top radiator in my system, as I have to occasionally, because it collects all the air in the system, and I noticed the system water pressure had got a bit low, so I topped it up. That's when my problems started...

The pressure wouldn't hold for more than a day - I looked everywhere for leaks, found none and so feared the worst: under-floor leaks. Then I came upon this thread.

So, following advice given above, I checked the pressure relief pipe outside and - yes - it was leaking, noticeably. I tried the operating it manually a few times to try and reseat it, but to no avail, the leak continued. So I replaced it (BES, about £6), only a 10 minute job - which must have saved me ££s in plumbers bills! The old one had lots of muck/rust on the rubber washer, so it was obvious it wasn't going to seal properly.

But, the pressure drops continued and I was a bit baffled. The odds on there being another leak, happening at the same time as the valve problems seemed rather remote. I followed the tip of tying a plastic bag over the pressure relief pipe and it was still leaking, albeit much less. At this point I also noticed that the water pressure rose significantly when the boiler heated up. So, following more advice above, I checked the expansion vessel air pressure. Almost no pressure in it! I pumped it up to 1 bar and the whole system has behaved fine since then. Hopefully, it will continue to do so.

I'd add that until last year, we were paying British Gas for an annual boiler service so it would seem the service did not include checking the EV pressure. The boiler is about 12 years old now and I doubt anyone has ever checked or adjusted the EV pressure in that time. Further, now the EV has the correct pressure, the system water pressure does not vary anywhere near as much as it did in the past, so I suspect the installer didn't check and confirm the correct EV pressure, either.

So, my thanks to everyone who contributed to this thread, as you’ve saved me a lot of money!

Digittt

Hi folks,


Recognize this is an old thread, but desperate for help. Our plumbers while being friendly don't fill me with any confidence that they will be able to find the problem efficiently...not sure whether any other plumber could do anything else.


So the background - central heating / radiator pipe leak. We are refilling the expansion tank twice a day now (!!!!) and have been for over a month...leak sealant was tried and failed. No visible signs of leak anywhere either on the ground or second floor. PRV has been checked and isn't the cause of the problem.


Plumbers are saying they need to start digging into the floor...the obvious worries are the cost and whether there is a way to do it with less damage to repair.


I seem to be the only person offering ideas to the plumber, but I have no idea on their validity. Would appreciate any input. My ideas so far are:


- The fluorescent dye mentioned above...let me know what dye it was if you may and I will see if I can procure. Issue is I don't believe the leak is at any radiators, suspect it is in a wall / under the ground. Do you think this still could help in that instance?


- Filling the whole system, and then completely switching off everything, including the pumps for a week or so. The idea hopefully being this helps us isolate if the leak is upstairs by how much the system empties. Issue being this relies (in my mind) on there being a single early branch between upstairs and downstairs feeds. Anyone with experience think there are any merits to this?


- Ultrasound damp meter - have no knowledge or experience of this and what it actually would show. But taking any ideas at this stage that don't involve digging up everywhere!


We have lived in the house for 4 years, the first 3 as tenants...while tenants we didn't have a single problem. We took ownership last August and since then the house seems to have turned into a pumpkin (electrics, plumbing etc etc). The one thing we have done differently since taking ownership is start using the underfloor hearing. It's in the kitchen and upstairs bathroom. Kitchen is definitely electric, the upstairs bathroom I am uncertain. Kitchen is far away from any piping, but upstairs it could be reasonably close. That being said, there's over 10l a day disappearing in the system, if it was upstairs in the middle of the flooring I would have expected to see damage somewhere. Anyway, enough rambling.


Let me know if anyone has some more / better ideas.

Thanks,


Digittt

eamon

I had similar problems. Eventually BG changed the heat exchanger (Vokera Linea 24) and after 2 weeks I think the issue is fixed. The engineer suspected a pin hole in the unit and confirmed this by looking at the exhaust gases, clouds of steam!. Something related to the layout of the boiler and the water dripping unto hot surfaces and instantly evaporating and out the flue. I had already eliminated pipe joint failure as I have lived in many damp houses and recognise the smell of stagnant water.

alanobrien

Digittt wrote: »

Hi folks,

- The fluorescent dye mentioned above...let me know what dye it was if you may and I will see if I can procure. Issue is I don't believe the leak is at any radiators, suspect it is in a wall / under the ground. Do you think this still could help in that instance?

Let me know if anyone has some more / better ideas.

Thanks,


Digittt

The dye is Fluorescein (powder or liquid) you can get it from ebay, you only need a small amount.

Digging up the floor should be a last resort and given it creates havoc i would not do that before every other idea had been exhausted. I did try a thermal imaging camera recently and they work ok on bare concrete floors but don't work where laminate is in place as it creates a thermal insulating barrier.

I would not discount the heat exchanger - per above, on my own system i have seen a perforated heat exchanger leak into the condensate drain so the leakage was effectively invisible. Good luck with the leakage tracing.

Digittt

Thanks chaps to both of you. Interesting what you say on the boiler. It is old and ultimately was the reason I started calling in the plumbers. It suddenly started struggling to switch on or wouldn't switch on at all. I thought it was replacement time, but they came in and said it was old, but of the type that just keeps going and going and would outlast anything we bought today.


They told me to keep it going (ie servicing / repairing as necessary) until the heat-exchanger eventually goes. This would be evident they said as water would be dripping out the bottom.


That was about 5 months ago. They came in 2 more time ahead of the full blown leak as the boiler stopped working (as the expansion tank was emptying over a long period, which I didn't spot - I didn't know at the time but this was the start of the leak). Would be one big coincidence if ~3 months after they give me that advice, it started having that problem.


Would the test be to switch it all off for a day? ie assuming the water leaks out and nothing is hot, hopefully I would see it somewhere?


Assuming that makes sense I will try this. Then after that I think will be the dye.


Regards,


Digittt

Rwill_2

I see this is an old thread but would appreciate advice. Have Worcester cdi boiler, installed just a year ago to previous owner.brand new house finished June 2013. I've only had the keys to the house for 4 weeks. Worcester engineer came out today under warranty as boiler totally loses all pressure everyday, goes from2 bar to zero in a matter of hours and then error code for over heating. He isolated the boiler from CH, pressure stayed constant, as soon as he reconnected went from 2.5 to 1.5 immediately. Then 1.5 to 1 in the next 30 mins. Left saying sorry love, not your boiler and good luck by the way, you've bought a poorly built house here. Helpful, not!! I asked him specifically about the expansion vessel but he said definitely not, must be a leak in the pipe work.

I have marble floors and tiled floors through the house so do not want to taking up the floor at all. My electric underfloor heating doesn't work in one bathroom either- could this be linked ie some pipe work damaged below the floor. The new house is still painted magnolia everywhere with white ceilings and there are no leaks visible anywhere, no leaks from the copper pipe outside, nothing from radiators (he bled them all). Could it be the heat exchanger on such a new boiler? Would this allow the pressure the drop so quickly?

As a woman who lives on her own it's easy to get really bamboozled by technicians and have been unimpressed with Worcester so far. Many thanks.

Crinkmeister

Leak on heat exchanger would have given you a pressure drop when heating circuit isolated, so problem is outside the boiler.

crazylady100

I have just seen this old thread as I have been having similar problems with my boiler losing pressure and the boiler engineer couldn't find where the leak was. We thought it might be under the tiles in the hall but the last thing I wanted was to start ripping the floor up to find the leak with all the expense and disruption that goes with that.
It turns out that the cost of finding the leak was covered on our insurance policy under what they call Trace and Access (trace the leak and access it). There are companies that specialise in this work and they find the leak by using a special heat camera and by introducing a special gas to the system which they then sniff out with a detector. We used a company called The Leak Team and they were able to pinpoint the leak to a pipe under the corner of the lounge, which is carpeted and therefore easy to pull back and fix. Much less disruption than hacking up the hall tiles and they found the leak on the first visit, which was such a relief after all the tooing and froing we had had already with plumbers etc.
I recommend that you check your insurance policy to see if you are covered for this sort of work. Having said that the company I used were so confident they would find the leak they said there would be no fee if they couldn't!

LRoss

Hi, I know this is an old thread, but looking to solve a similar problem with our boiler losing pressure with no obvious leaks above floor level. Can you tell me, did you have to lift your floors to use the uv light method? Thanks!