Dropping combi boiler pressure - finding the leak?

[my_name_is_slim_daisy]

Hi @paulc i actually have this type of filter. Any step by step guide that can explain how to do this?

Also does the system need draining in order to use the leak sealant?

 

[my_name_is_slim_daisy]

Close the two valves at the ends of the flexible hose (lever at right angles to the hose) (at least one of them should normally be closed). Unscrew the end of the hose farthest away from the boiler pipework using the metal "wings". The water left in the short section of hose will come out but it will be a tiny amount. Attach the hose to the can. Slowly open the valve on the pipework side. If no leak then pull the trigger to discharge the can. Once can is empty close the valve again. Unscrew the can. Reattach the filler hose to the water main side. Top up as needed. I don't think the can leaking is a high risk unless you are really cack handed at attaching the hose. If anything goes wrong just close the valves and seek help.

I’m having a bit of trouble mapping this, so I’ve attached pictures. The flexible hose you’re referring to is the white plastic thingy or the black hose? As I’m writing this it seems you’re referring to the gold/brass thing?

Also if I end up getting help, I’m trying to understand if for the leak sealant, they’d need to drain the system? Doesn’t seem like it

 

[my_name_is_slim_daisy]

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[my_name_is_slim_daisy]

It seems like with the Fernox F4 Express Leak Sealer, draining is not needed. From your experience would you recommend this leak sealant? (Apologies to OP if I’m hijacking the thread).

I’m also wondering after dispensing the leak sealant, how long before I can dispense the inhibitor (via the filter)? I’m reading that anything between 1-24 hours. In my case it’s a “pinhole” leak so I’m hoping 1-2 hours is ok?

 

[paulc]

Your filter appears to be a Spirotech model. Installation instructions claim that isolation valves are not required.

Filling loops don't always use flexible hoses - Mine (a Viessmann 050) is a short rigid pipe underneath the boiler connecting the cold water to the CH return with a small valve either end.

You don't need to drain the system to add a sealant, but if you do, you'll also need to add an inhibitor at the same time.

 

[my_name_is_slim_daisy]

@paulc from what I remember the filter was packaged as the “Vaillant 22mm Boiler Protection Kit”, which states: doesn’t require shut-off valves or bypass, it boasts a hassle-free setup and easy maintenance (which still doesn’t mean a lot to me at the minute as I’m still confused )

 

[Stevers]

To keep things simple I only use Fernox products, and for inhibitor top ups use F1 Express to inject into my by-pass radiator which I can easily isolate to remove the bleed screw ready to fit the injection nozzle. I have the brass Fernox TF1 magnetic filter but this is high up on a wall above the boiler so much less accessible than the shower room radiator.

However my system is still a gravity system so after my fourth or fifth session of scooping vile smelling gloop from the header tank I added F7 Biocide and two bottles of F1 Inhibitor to the tank as I was in a position to treat from a now clean and empty tank. A header tank in the roof definitely a mixed blessing!

 

[my_name_is_slim_daisy]

Thank you all (I have some homework to do - understand shutoff valves, filling loops and bypass ) I shall also stick to Fernox since the installer also used that last year.

I’ve decided to let a plumber dispense the leak sealant, but I will watch them do it. After around 24 hours I plan to then dispense the Fernox F1 inhibitor via the magnetic filter.

 

[claraclattermole]

We have had a mysterious leak for a few years and it turned out to be leaking and running under the tiles in the kitchen which has under floor heating. So the leak was just evaporating. Could it be something like that?

 

[lizziecupcakes]

hi all,

I really need some quick advice.
The boiler pressure dropped from 1.4 to 1.3 today. I'm not sure if it's because of the cold, but i do think it's because of the leak we can't find.

I had the plumber round just now too - it was someone my partner found, I don't know who he is.

The main reason he is round is to check whether the inhibitor level is ok - he removed about 100mls from the central heating system and tested it with a litmus paper. He said this turned the colour he expected. I thought this was a lot to remove just to do a litmus test. Is 100mls too much?

My concern is the boiler pressure again - I assume it has dropped significantly.

He then turned on the heating right away, which has made the pressure spike so I don't know what the pressure is at all now (on cold) and I've asked him to stop his work and now have to wait for the system to settle.

Then my partner asked the plumber to add sealer and then the plumber went away to prepare that in his van (but the system still hasn't settled). When he returned, the plumber said that he has to inject it the sealer via the radiator and not the boiler itself, which confused me. He said he can't see how to do that on our ecotech vaillant at all. I asked him not to do anything as he also started looking through the boiler manual and it made me think he just doesn't know what he's doing??

So to summarise:
- apparently the inhibitor level is ok.
- i'm waiting for the boiler/system to settle before we know the new pressure
- the sealer was not added as I just didn't feel he knew what he was doing - is it ok to add it via one of the radiators?

The Plumber really made me nervous and I just don't know whether to trust him. wdyt? I panicked about the sealer part and just wanted him to stop.

If the boiler pressure has dropped significantly, i I'll have to top it up again which defeats the whole purpose of the inhibitor, which is now being further diluted.

 

[Cubist]

What make and model of boiler do you have? Was the CH system operating for several days before it was switched off to let it cool? Most combi boilers operate in the range 1 to 1.5 bar when cold quite happily. A reading of 1.3 should be nothing to worry about and does not typically signify a leak.

 

[lizziecupcakes]

What make and model of boiler do you have? Was the CH system operating for several days before it was switched off to let it cool? Most combi boilers operate in the range 1 to 1.5 bar when cold quite happily. A reading of 1.3 should be nothing to worry about and does not typically signify a leak.

thank you.

Can sealer be added via a radiator? I wasn't sure about that.

The boiler I have is the new vaillant ecotech - installed 2024.

My boiler pressure was 1.7 a couple of months a go and now 1.3 (it's been doing this over the past year.).

The plumber put the system back on (hot) and the highest reading is 1.5 (which makes me think when it is cold, it will be below 1) since he removed some water from the system to do a litmus test.

I turned off the heating to let it go cold again. I just feel worried that he has made things worse and mainly, Can sealer be added via a radiator rather than the boiler itself?

 

[paulc]

Can sealer be added via a radiator? I wasn't sure about that.

Chemicals can be added via a radiator - It is how I dose my system. I have a short length of flexible hose that will screw in to a capped bung hole with a funnel on the other end (something I cobbled together in the garage). Before adding chemicals, the system gets drained down partially. Less mess than shutting a radiator off and having to go through the hassle of balancing it again afterwards.

 

[Flyfisher]

I can't see why inhibitors can't be added anywhere within a system given that within a few minutes of the heating pump switching on the contents will have been pumped throughout the system, as intended. Therefore, it makes sense to me that any additives should be added at the most convenient point within the system. If that happens to be a radiator then fair enough.

Regarding the removal of 100ml for test purposes, I don't know the total capacity of the system in question but I would guess it must surely be many tens of litres, so I'd be very surprised if the removal of 100ml would make a significant difference to anything.

As for the system pressure, our Vaillant ecoTech boiler (c.2014) pressure monitor has always shown pressure variations of around 0.5 bar depending whether it is running or not. I believe the operating pressure range is 0.8 - 3.0 bar and whenever I top up the pressure (via the filling loop) I aim for 2.0 bar. In this way, a pressure variation of 0.5 bar makes no difference to the operation of the boiler.

However, as I've previously mentioned, sometimes, for no known reason but often after a period of non-operation, the pressure seems to suddenly drop to 0.0 bar, thus preventing the boiler from operating. I've no idea why this happens and just refill the system to 2.0 bar and it then works as normal. I've never found any sign of leakage anywhere accessible.

 

[Cubist]

The internal pressure of the CH system will always vary according to the temperature of the water as it rises and falls during operation. Should the pressure fall below a given minimum OR exceed a given maximum the internal sensors will shut down the system or prevent it from being powered up. The pressure meters used in these systems are far from being throughly accurate and reliable and whilst they do provide a useful guide they should not be considered an absolute measure of the internal water pressure.

A golden physical rule though is that the pressure will be greatest when the system is hot and lowest when its thoroughly cold BUT the lower pressure reading will also be influenced by external factors such as the ambient temperature indoors. As a consequence, any pressure readings you record and perhaps act upon should be based on observations taken only when the system is in full operation and the radiators are hot AND when the system has been switched off and allowed to thoroughly cool - but you must also remember that the temperature of the systems water may take several days to fall to its lowest value and therefore its lowest pressure (this is why some combi boilers refuse to start up after they have been left unused for several days).

I hope the above helps as I do think you're needlessly worrying about nothing at the moment.

 

[lizziecupcakes]

Thanks everyone.
You've all been so helpful, I really appreciate it.
I think it's highly possible I am worrying about nothing. I just worry we are damaging the boiler and will need to replace in a few years when we already spent £4.5k on it (inc the ecotec vaillant, the labour and a tiny bit of pipe changes).

I can't believe how little I know about anything about houses!

I hope to be a different person in a few years and able to give lots of advice to people who need it like you all do on here! (I don't think you all realise how much your help means to us - thank you so much!)

 

[Flyfisher]

A golden physical rule though is that the pressure will be greatest when the system is hot and lowest when its thoroughly cold BUT the lower pressure reading will also be influenced by external factors such as the ambient temperature indoors. As a consequence, any pressure readings you record and perhaps act upon should be based on observations taken only when the system is in full operation and the radiators are hot AND when the system has been switched off and allowed to thoroughly cool - but you must also remember that the temperature of the systems water may take several days to fall to its lowest value and therefore its lowest pressure (this is why some combi boilers refuse to start up after they have been left unused for several days).

That's a good point and quite possibly the reason for our pressure to drop below the boiler minimum after a period of disuse. But I think there's also something else going on because the pressure dropped too low a couple of weeks ago and required topping up again before the boiler would restart. This time, I was at home and noticed it after a few hours, even though the boiler had been operating every day since the onset of colder weather, so the overall system had certainly not had time to cool down to ambient temperratures.

Now that I can switch the system on/off remotely, these pressure drops have become a bit of a nuisance when I get home to a cold house (ok, first world problem!) so I've wondered about fitting a motorised valve to the filling loop, but I'm nervous of this as I can't remotely measure the system pressure and could easily over-pressure the system by 'blindly' opening/closing the valve. The other thing I've considered is fitting a pressure regulator within the filling loop.

Actually, we already have a pressure regulator limiting the incoming mains supply to the house to 3 bar, so I wonder why such things are not fitted to filling loops? I suppose it could cause problems in the event of an actual leak, but perhaps a combination of a motorised valve and a pressure regulator would work in terms of remote control? Hmm.

 

[Cubist]

Thanks everyone.
You've all been so helpful, I really appreciate it.
I think it's highly possible I am worrying about nothing. I just worry we are damaging the boiler and will need to replace in a few years when we already spent £4.5k on it (inc the ecotec vaillant, the labour and a tiny bit of pipe changes).

I can't believe how little I know about anything about houses!

I hope to be a different person in a few years and able to give lots of advice to people who need it like you all do on here! (I don't think you all realise how much your help means to us - thank you so much!)

You're very welcome. We all operate on a 'Pay it Forward' basis having been the beneficiaries of aid and advice from others in the past - you'll be very welcome to the club. Take care and Merry Christmas,

Cubist

 

[Stevers]

I wonder why such things are not fitted to filling loops?

Likely to avoid accidental contamination of the potable water supply with the tainted and treated water of the heating system.

Some sort of header tank in the loft could provide the necessary constant pressure for such a filling loop - without any risk of contamination to the supply!

 

[Cubist]

That's a good point and quite possibly the reason for our pressure to drop below the boiler minimum after a period of disuse. But I think there's also something else going on because the pressure dropped too low a couple of weeks ago and required topping up again before the boiler would restart. This time, I was at home and noticed it after a few hours, even though the boiler had been operating every day since the onset of colder weather, so the overall system had certainly not had time to cool down to ambient temperratures.

Now that I can switch the system on/off remotely, these pressure drops have become a bit of a nuisance when I get home to a cold house (ok, first world problem!) so I've wondered about fitting a motorised valve to the filling loop, but I'm nervous of this as I can't remotely measure the system pressure and could easily over-pressure the system by 'blindly' opening/closing the valve. The other thing I've considered is fitting a pressure regulator within the filling loop.

Actually, we already have a pressure regulator limiting the incoming mains supply to the house to 3 bar, so I wonder why such things are not fitted to filling loops? I suppose it could cause problems in the event of an actual leak, but perhaps a combination of a motorised valve and a pressure regulator would work in terms of remote control? Hmm.

Theres another factor that is, to my mind, seldom if ever taken into account. Like most other metals copper expands and contracts, as do steel radiators, and as they do the pressure on the contained fluid conversely increases or reduces. One would expect such changes to have only a slight effect but it could perhaps be enough in some installations to trigger a sensor cut out?