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Hi
Iv been trying to find a leak on a central heating system for a few days now but haven't found nothing obvious. I took up the floorboards downstairs and everything looks good.

Another gas engineer has recommended I use central heating sealants as they can be quite effective but a second gas engineer thinks they're no good.

So what do you guys think? Are they any good? If so which one would you recommend?
Thanks in advance.
 

aggis

Plumber
Gas Engineer
I use them, find Fernox F4 is probably the best.
It really depends on the size of system, the cheaper stuff like instinct works well on smaller systems, up to 6-7 rads. Bigger than that double dose.
Always check with the Manufacturers of the boiler if under warrant, that they’re happy.
If I’m adding it to a sealed system, I initially leave the pressure as low as I can, max 1 bar & inform the customer to top it up if required in a couple of days or so.
Sometimes when returning later to do service job when repressurizing the expansion vessel you may need to top it up.
 

oz-plumber

Esteemed
Plumber
More info on the system and when it leaks.
Leaks all the time or only when it is warm or hot.

How much does the system leak?
 
Don’t use a sealant, unless you know exactly where the leak is and you cannot access it.
I have a good idea about where the leak is but I cant access it because the leak is beneath the downstairs bathroom and the customer doesnt want to remove the floor tiles.
More info on the system and when it leaks.
Leaks all the time or only when it is warm or hot.

How much does the system leak?
It leaks all the time. Even if the boiler is off. Tends to go from 1 bar to 0.2 bars in 24 hours so needs topping up daily.

The house has a vokera non condensing boiler. Prv isn't dripping and the expansion vessel has the correct air pressure.

House has 7 rads which have been taken off temporarily for decorating and 2 towel rads which are still connected and working well.
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I use them, find Fernox F4 is probably the best.
It really depends on the size of system, the cheaper stuff like instinct works well on smaller systems, up to 6-7 rads. Bigger than that double dose.
Always check with the Manufacturers of the boiler if under warrant, that they’re happy.
If I’m adding it to a sealed system, I initially leave the pressure as low as I can, max 1 bar & inform the customer to top it up if required in a couple of days or so.
Sometimes when returning later to do service job when repressurizing the expansion vessel you may need to top it up.
Thank you. I have heard some praise for the fernox f4. Might be giving it a go.
 

aggis

Plumber
Gas Engineer
I have a good idea about where the leak is but I cant access it because the leak is beneath the downstairs bathroom and the customer doesnt want to remove the floor tiles.


It leaks all the time. Even if the boiler is off. Tends to go from 1 bar to 0.2 bars in 24 hours so needs topping up daily.

The house has a vokera non condensing boiler. Prv isn't dripping and the expansion vessel has the correct air pressure.

House has 7 rads which have been taken off temporarily for decorating and 2 towel rads which are still connected and working well.
Post automatically merged:



Thank you. I have heard some praise for the fernox f4. Might be giving it a go.
Hello if its a Vokera Linea or other earlier boilers with copper heat exchangers, take a look at the back left hand side, bottom of the H exch. As had many of these leaking, best time to spot is when thoroughly cold. As when being used it can dry up, often looks a bit dirty in the corner & the fibre board gets stained. If it’s that then new H exch.
 

oz-plumber

Esteemed
Plumber
While the rads are off, cap the valves and pump the system up to 5 bar, 500 kPa or there abouts.
Disconnect the boiler from the piping and test from where you can.
That will give you a definitive answer if the pipework is leaking.

As far as I am concerned, leak sealers are only remedial.

Testing the expansion vessel, I generally de-pressurise the system to test this, because the water pressure on the wet side of the bladder can give you false pressure readings.
 

centralheatking

Esteemed
Plumber
Hi
Iv been trying to find a leak on a central heating system for a few days now but haven't found nothing obvious. I took up the floorboards downstairs and everything looks good.

Another gas engineer has recommended I use central heating sealants as they can be quite effective but a second gas engineer thinks they're no good.

So what do you guys think? Are they any good? If so which one would you recommend?
Thanks in advance.
Answer NO and they can clog up boilers and pumps and invalidate guarantee. It’s a quick fix used by diy people any tradesman that suggests it should be rejected. Centralheatking
 
Hello if its a Vokera Linea or other earlier boilers with copper heat exchangers, take a look at the back left hand side, bottom of the H exch. As had many of these leaking, best time to spot is when thoroughly cold. As when being used it can dry up, often looks a bit dirty in the corner & the fibre board gets stained. If it’s that then new H exch.
Thanks for the tip. As it happens, the boiler is a vokera linea but the heat exchanger is fine. Im only saying this because the boiler was serviced a few weeks ago and at the time the boiler was fine however the pressure loss problem precedes the boiler service.


What I have done today is isolate the upstairs circuit and cut both the 22mm f and r pipes for the downstairs circuit and capped them off. Now Im testing the pressure in the 22mm pipes downstairs that are about 4m in length. If the pressure drops tonight, I know that 1 or both of these pipes needs to be replaced. I might not go down the sealant route but access is sooo hard, I might have to reluctantly try the fernox f4.
 
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centralheatking

Esteemed
Plumber
Thanks for the tip. As it happens, the boiler is a vokera linea but the heat exchanger is fine. Im only saying this because the boiler was serviced a few weeks ago and at the time the boiler was fine however the pressure loss problem precedes the boiler service.


What I have done today is isolate the upstairs circuit and cut both the 22mm f and r pipes for the downstairs circuit and capped them off. Now Im testing the pressure in the 22mm pipes downstairs that are about 4m in length. If the pressure drops tonight, I know that 1 or both of these pipes needs to be replaced. I might not go down the sealant route but access is sooo hard, I might have to reluctantly try the fernox f4.
By your account it appears you are being quite forensic in your approach in locating the leak. Out of interest by how much is it dropping over what timescale...I an experienced in this area and may be able to assist you. Centralheatking
 
By your account it appears you are being quite forensic in your approach in locating the leak. Out of interest by how much is it dropping over what timescale...I an experienced in this area and may be able to assist you. Centralheatking
I certainly hope you can.
The system will go from 1.25bars to 0bars of pressure over 24 hours so needs to be topped up daily. I couldnt tell you how many litres because I haven't timed how long the filling loop tap is on for before the correct pressure is reached.

If I do time it, Id have to disconnect the filling loop and fill a bucket for the same time and measure the litres that way. Dont know if thats any benefit though.
 

Stigster

Esteemed
Plumber
My opinion of leak sealers is as an emergency measure only. If you need to keep a system limping along for a week or two until it can be fixed properly. A vulnerable household with a pressure loss situation in the pipework that cannot easily be accessed, that kind of thing. I would say as much, put in writing that it isn't a repair too. Say why it was done. Make sure you both have a copy. I wouldn't want a homeowner failing to fix the actual problem and down the line blaming me by telling an insurance company or whoever "He fixed it with leak sealer" when it caused damage further down the line. You know most customers wouldn't try that on but you know some would.

It's not something I would ever use beyond that and similar scenarios.
 

centralheatking

Esteemed
Plumber
I certainly hope you can.
The system will go from 1.25bars to 0bars of pressure over 24 hours so needs to be topped up daily. I couldnt tell you how many litres because I haven't timed how long the filling loop tap is on for before the correct pressure is reached.

If I do time it, Id have to disconnect the filling loop and fill a bucket for the same time and measure the litres that way. Dont know if thats any benefit though.
If you are in an average sized house then the difference between 1.5 bar and zero can be as little as 2 litre or less but with the frequency then this is not a small difficult to find leak like a bead of water on a rad valve or fitting. So you are looking for quite a volume of water. I would blow it up to 2 bar see if it shows itself listening is a good method at 2 bar. Have you checked under the boiler and outside the pressure release. If this was under the boards upstairs it would show on ceiling below. So it’s in a stud wall or under the floor downstairs where you will not see it. Keep in touch. Centralheatking
 

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