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Tim JA
Tim JA, Customer Service
Category: Appliance
Satisfied Customers: 2307
Experience:  Owner at Self-employed
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Our boiler is losing pressure to the extent that I am daily

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Our boiler is losing pressure to the extent that I am daily topping it up. The boiler was serviced last week and is in good condition. This suggests a leak somewhere in the system which the service engineer says must be either in the upstairs radiators or in the downstairs underfloor heating. He has checked all the radiators and finds no problem, and there is no indication of water damage in any ceiling downstairs. He also turned all taps off (and the pump) connected to the underfloor heating pipework.....that's why I'm contacting you as Danfoss Randall is on a white box by the pump. These taps have now been turned off for 4 days, presumably isolating the underfloor pipes. But the pressure is still falling and I'm still topping it up daily. My main question is does the fact that the underfloor taps etc have been turned off for 43 days mean that the leak is not in the underfloor heating pipes?
JA: Where does the leak seem to be coming from?
Customer: This is the problem. The service engineer (me too) is at a complete loss as to where it can be as there are no visible signs anywhere in the house of a leak.
JA: How long has this been going on with your boiler? What have you tried so far?
Customer: Up until about 2 months ago I had needed to top up the boiler about 3 monthly. About 2 months ago at the start of a cold spell I turned all the upstairs radiators on (we hardly ever use them) and since then I've needed to top up every day. But as I say there is no sign on or near the radiators of a leak, and no sign of water damage on the downstairs ceilings. The engineer first suggested that the expansion valve on the boiler may need to be replaced, and he has now done that, but it has made no difference.
JA: Anything else we should know to help you best?
Customer: I can't really throw any more light on the problem. I did wonder if some staining on the lounge carpet might indicate a problem with water rising through the floor below, so pulled up half of the big lounge carpet and underlay to take a look, but it was dry so far as I could tell.

Good morning, welcome to the Technical section in JustAnswer; my name is ***** ***** I will help you today.

We need to work through this systematically, so there will be some tests I ask you to do, and monitoring over a period of hours, so please don't expect an instant answer. I'll come back to your specific questions shortly, but first please secure a polythene bag ( with no holes in ) under the end of the copper discharge pipe on the outside wall where the boiler is mounted. Top up the pressure, preferably when the boiler is cold, and then wait for the pressure to fall. Then let me know if there is any water in the bag.

To be objective about this, please tell me the following pressure readings:

1. Before you top up;
2. After you top up;
3. After it has dropped again.

Also, please provide the make and complete model number of the boiler.

If you receive a phone call offer, please ignore it - these are system generated and outside my control. My understanding is that you won't be charged if there's no phone call.

Customer: replied 1 year ago.
Thank you Tim. I can respond to your questions immediately. For the last 4 weeks I have had a small container under the end of the discharge pipe and there has not yet been any water in it. With regard to your 3 points, as follows:-
1. Early each morning I have found it to be down to 0.1 in the red segment..
2. At 6.30am each morning I have been topping it up to 1.
3. It has slowly gone down over the day and by 10pm it is down to 0.5 (ie on the edge of the red segment), and
by 6.30am the next morning is down again to 0.1 (in the red segment).
NB I have had no heating on at all for the last 6 weeks. The hot water has been set to come on at 7am and go off at 6.30pm each day. So the pressure has continued to fall during the night when there has bee no heating or hot water switched on. The boiler is a Vokera (Mynute 28e). Serial no: 139042 50236.

Impeccably clear and accurate answers - thank you!

The amount of water that you're adding is going somewhere, and unless it's being sprayed into the combustion chamber through a hole in the heat exchanger and disappearing out of the flue, then it must be leaking from the primary pipework somewhere. If it were leaking from anywhere on the 1st floor I would expect you to have seen water on the ground floor. If it's leaking from pipework under, or embedded in, the floor, then of course it could be disappearing.

You mentioned closing the isolating valves on the UFH installation. You can't assume that the valves are working, so do you have a pressure gauge on the UFH manifold in evidence that no water was being lost there? If not, then install one pronto!

(BTW, on a pedantic point, as a contractor I would never report that "there is no problem" when looking for a leak and inspecting something. All that anyone can saw is that the fault hasn't been found yet, and until you know where it is, nobody can say where it isn't. This is more than just an existential conundrum - it's important to stay open-minded in a hunt for a leak, and mentally closing off possibilities is conducive to making mistakes.)

Customer: replied 1 year ago.
Thank you, ***** ***** your response. I don't know if there is a pressure guage on the UFH manifold, and don't I don't think I'd recognise one if I saw one. So maybe my next step should be to get our engineer back to take a look and, if necessary, install one. Would you agree? He did say when last here that there is always the possibility that the valves may not be working as they should. From what you say it seems more probable that the leak is in the underfloor which case how, other than by islolating it, can this be confirmed, and how can the location of a leak be identified? I would be very scared to learn that all downstairs flooring needed to be dug up.....and probably broke by the end of it!

Apologies for the delay - I was out for a while. I will digest your post now and reply ASAP...

Leaks in UFH systems to happen, but lets stay positive. Even if you have one, you don't necessarily need the entire installation to be dug up - there are specialist ways of detecting the location of the leak and then a localised repair can be done.

There is an easy test for you to do without having to pay your engineer to do any work. All it needs is for you to identify and operate the two isolating valves for the UFH. If you don't know where they are, please take a photo of the UFH manifold and the area around it, and I'll tell you where the valves are. The photo doesn't need to be a close up, just in focus and well-lit. After that I can tell you the steps for the easy test.

Customer: replied 1 year ago.
This technology is new to me, but I think I've attached a photo. Has it reached you?

Good work. Yes I can see it. Bear with me...

Sorry for the delay - I was on a phone call. Please could you take a much wider angle shot of the manifold and surrounding pipework?

Customer: replied 1 year ago.
Is this better?

Excellent! Now, do you have a radiator vent key? Something like this one?

Customer: replied 1 year ago.
I do.

OK. On the upper right of the manifold there is a vent. Your key should fit that. Get an old towel ready.

1. Assuming that both red and both blue valve handles are still in the closed position as shown in your photo, go ahead and open that vent. You should little or no water emerging. If you do, it should peter out very quickly.

2. If the water doesn't stop pretty quickly, that suggests that at least two of the valves don't work and you can't continue. Let me know if that's the case.

3. If the water stops, then check the system pressure and top it up if needed. When the pressure is up to 1.0 bar, if water is still not coming out of the vent, then the valves are working, so close the vent, and open both of the blue valves, then close them again.

4. Wait 24 hours.

5. Repeat step 1. This time you should get a stronger jet of water that might last longer before it peters out.

Let me know how all of that goes.

Customer: replied 1 year ago.
About to run through these steps, but before I do could you please clarify on 2 points:- 1. There is a similar vent to the right of the lower set of pipes. Do I need to open that one too, or just the upper one? 2. After doing step one, I assume that I should close the vent (or vents?) again before proceeding to step three. Is that correct?

1. You don't need to open the other vent. It would do no harm to open it, but then you have two vents to close, and if you want to do so in a hurry then that can be inconvenient.

2. Yes. My step 2 should have said "Close the vent and let me know..." Apologies. Well spotted.

Customer: replied 1 year ago.
Hi Tim. I have completed the 5 steps. It has behaved as you said it should at every stage. And this morning, I again had to top up the boiler's before the hot water came on, as it had again dropped to near the bottom of the red segment. Paul.

Hi Paul

OK. Give me a moment to refresh my memory of the steps - 24 hours is a long time in the heating industry ;-)

Right. That is a strong confirmation that the leak is not in the underfloor loop. That's probably good news for you.

However, it doesn't solve the mystery because you still have a leak somewhere. I'm excluding a heat exchanger leak because you lose pressure when the boiler isn't burning. As I said at the outset I doubt that it could be from the first floor, so the focus now should be on the ground floor.

Do you have concrete floors throughout, or some suspended floors?

Customer: replied 1 year ago.
Hi Tim. Thank you for your speedy response. I don't know the answer to your question about the downstairs flooring. All I can see is that it is screed throughout. The house is around 35 years old, and we have been here for 6 years. I don'l know how I could find the answer to you question. Paul,

Hi Paul

"screed throughout" is the answer to my question, so that's fine.

If you're absolutely 100% certain that nothing is coming out of the PRV discharge pipe, then I think your next step is audio and heat tracing. With sensitive leak detection equipment, accurate tracing can be achieved of water 'squirting' out of a leak in concrete. I don't have that equipment but specialist leak-tracing contractors do, so that's the direction I would be going now that the obvious suspects have been all but eliminated.

Customer: replied 1 year ago.
Hi Tim. Thank you, ***** ***** your response. You have been an enormous help to me over that last 2/3 days, and not least in keeping me calm! I think from what you say in your last response is right, and that what I need to do now is to contact a leak detection service in my local area. I have seen on my browser a company called LDS Leak Detection Service Ltd whch (to quote) "offers a non-destructive leak detection service using specialist equipment to find hidden water leaks accurately in any pipework and heating system in Exeter and throughout Devon." Sounds like what I'm looking for. Would you agree?

Hi Paul

That sounds like the service you need. I'll just have a quick look at their web site...

Yes that sounds professional. I can't see any spelling mistakes on the web site, which bodes well. And I like this:

"On completion of our Leak Detection Survey we provide a fully comprehensive leak detection report including colour photographs and recommendations. You will then be able to make arrangements with your local plumber to fix the leak." they aren't trying to tie you in to using them for the fix.

Customer: replied 1 year ago.
Thank you Tim. You have been enormously helpful to me over all this: quick, efficient, and with really clear instructions that even a DIY novice like me could understand and feel confident in following. I really appreciate it and am extremely grateful. Wearing my retired vicar's hat, I say "Bless you." Paul.

You're welcome, Paul :-)

This is an opportune moment to ask you to rate my assistance, using the 5 stars at the top of the page. The customer's rating is what enables an expert to be paid for their time, so I'm glad to hear that I was helpful to you :-)

Tim JA and other Appliance Specialists are ready to help you

Thank you for your rating, Paul, and your very kind bonus :-)

By the way I will be interested to hear the outcome!

Customer: replied 1 year ago.
I'll let you know how it I do that via this chatline? I think that I'm only allowed to be on it for a week???

You can always email me at :***@******.***