1. Things you need to know about the new ‘Conversations’ PM system:

    a) DO NOT REPLY TO THE NOTIFICATION EMAIL! I get them, not the intended recipient. I get a lot of them and I do not want them! It is just a notification, log into the site and reply from there.

    b) To delete old conversations use the ‘Leave conversation’ option. This is just delete by another name.
    Dismiss Notice

C-Tec Miracle seal for leaks. Anyone used it?

Discussion in 'off topic' started by Mike Reed, Jan 15, 2023.

  1. venton

    venton pfm Member

    If it's a small leak on a straight run of pipe, the fernox may stop it. But if it's on a joint, it may not completely seal it. I've seen what the Fernox stuff does, it weeps out the hole and dries into a hardish glue on exposure to air. Bit like pva glue when it hardens. But if it's on a joint, the glue hardens, and may not deal with expansion and contraction. Fingers crossed for you.
    Mike Reed likes this.
  2. twotone

    twotone pfm Member

    I've a load of LSX in the shed somewhere which I offered to Mike FOC but there's no way I'd be putting that into a heating system with a brand new boiler.

    Mike give Valliant tech support a call and ask them if they recommend you using leak sealer, I'm willing to bet that they'll tell you that you'll void the boiler warranty by using it as said above it goes rock solid and that will only end up blocking the heat exchanger.

    0844 693 3133

    0344 693 3133
    Mike Reed likes this.
  3. Davd

    Davd pfm Member

    got to agree with a lot of the other posters-your heating engineers is offering a sub optimal service and possibly taking advantage of your laidback nature. I would consider getting another engineer out from the boiler manufacturer and giving your trusted guy his papers-if he can't sort out the problem when you need him(depths of winter) what use is he?. i bet he wasn't slow taking the 4k
    twotone likes this.
  4. Mike Reed

    Mike Reed pfm Member

    Tony, I'm loath to create a problem here by contacting Vaillant, as the boiler is under a long guarantee as registered by my old (and current CP12) plumber. After all, sealant has been used so the die is cast, as it were. Should anything happen to the boiler, he'd activate the guarantee repair regardless (unless he totally retires of course).

    It's a waiting and monitoring game, as no major alternative solutions can be even thought about until late spring.

    I rather think that it's a joint, as expansion and contraction from higher that previously seen temp's would, i.m.o., be unlikely to burst a pipe run. Obv. guesswork, but the water temp. went from 3.5 max out of 5 on the v. old Potterton to 75 degrees on this one. I deliberately never ran the old one hard, which may be why it lasted 35 odd years (21 with me).

    How much air there is around those underground joints for the sealant to work is anybody's guess.
  5. Rug Doc

    Rug Doc pfm Member

    Is that how they work? When they come in contact with air? Clever.
  6. notaclue

    notaclue pfm Member

    Fernox should be pretty safe. Very well known brand. I Googled and, for example, Worcester say Fernox F4 is fine to use

    Might be wise to wary about any unusual/strong German sealer. Though Vaillant is German, of course, so unusual here could be well known in Germany.
    Mike Reed likes this.
  7. venton

    venton pfm Member

    Fernox replied to question "is the repair permanent?" with "Fernox F4 Leak Sealer can be used as a permanent repair assuming air contact at the failure site. Please note if the system is drained for any reason the F4 would need to be reapplied".
    Mike Reed likes this.
  8. twotone

    twotone pfm Member

    Mike if the heat exchanger fails or becomes blocked Valliant's engineer will test the water in the heating system then you'll know if they don't recommend the leak sealer or not.

    All of the boiler manufacturer's engineers test the water quality in heating systems as a matter of course these days even if they are only doing a non-leak repair/inspection ie changing a fan for example.

    Some manufacturers use water quality as a get out of warranties no idea about Valliant though, their boilers are few and far between up here but I do know that Baxi/Potterton, Ideal, Worcester Bosch and Vokera all test the water quality in the heating system when they attend for a warranty repair.
    Mike Reed likes this.
  9. twotone

    twotone pfm Member

    Personally there's no way that I'd use any leak sealer on a heating system with a practically brand new boiler, especially one that costs about £1400.
  10. venton

    venton pfm Member

    That's good to hear. Leak sealer is for desperate amateurs.
    twotone likes this.
  11. Mike Reed

    Mike Reed pfm Member

    Next CP12 (sorry, Gas Safe) inspection will be next November, Tony, when the Magnaclean filter will be inspected/cleaned. Didn't know about the water quality check, though it's my plumber/installer who used it, so the onus, as far as I can see, is on him and effectively on the Vaillant agent who registered it. Anyway, Hobson's choice here; sth had to be done, temporary or not.

    Third day of monitoring header tank/ingress/leak etc. in conjunction with the flow temp. No leaking when boiler is on and/or the flow temp. is 40 or above (room 'stat at 16). Around 30 to 35, the mains ingress starts to drip (but just a drip; not the flow as previously). This immediately stops when the boiler fires up and flow temp. increases. Obv. still dodgy but this appears to be an improvement. What will happen when we stop using 24/7 htg, I don't know but sooner or later, this'll have to happen. What'll happen when we stop having htg in the spring if there's still a leak, I don't know, as the system will need to be drained down again.

    What a palaver ! I'd be tempted to but this Miracle Seal stuff and add to the system but don't want to take any initiative/responsibility for obv. reasons.
  12. twotone

    twotone pfm Member

    Think I'd be selling up Mike if I were you if you can't face the disruption of finding the leak.

    Good luck.


    BTW, we, ordinary service engineers, ie not manufacturer's engineers are now supposed to test water quality of the heating system and record the result in the boiler service record, I've actually just bought a box of Fernox test strips for this purpose for boilers installed in the last year.

    The leak sealer chemicals probably won't show up in the water test which is just basically litmus paper but the test strip is supposed to be sent to Fernox for analysis and record on their app along with the boiler service record wether most guys who are doing services will actually do all of that during a service is moot cause the customer will have to pay for that service so that will bump the cost of a service up and it's hard enough to get punters to have a service done without increasing the cost of it.
    Last edited: Jan 26, 2023
  13. twotone

    twotone pfm Member

    Mike, were you charged for the work re the leak sealer?
  14. notaclue

    notaclue pfm Member

    I suppose you should be grateful that you didn't get a combi and pressurise the old pipes!

    If it were me, I would attempt to soldier on till the weather warms up (if the leak allows) and then get a company in that specialises in leak detection. Go for a proper fix. With the right gear, they might find and fix in a day.
    twotone, Mike Reed and Rug Doc like this.
  15. Rug Doc

    Rug Doc pfm Member

    That’s a good idea.

    Mike, would you like me to send you my damp meter? It might even pickup the leak in the ground if you follow the pipe run in the concrete? (Can you feel the warmth of the pipes underfoot??
    twotone and Mike Reed like this.
  16. Mike Reed

    Mike Reed pfm Member

    Not to my knowledge, Tony, and it didn't occur to me that I would

    Not at all; just pissed off as I went through all the pros and cons of the 3 systems (combi, sealed or stay as is) and it became obvious that with my underground layout it was best to safest to stay as is with gravity feed. The plumber agreed and was aware of my reasons. I may add, helped by input from pfm back in the summer when I was getting quotes/advice etc.

    Don't have a choice; that's the only game in town at the mo', though contacting my insurance co if the leak fails to seal is definitely a route to take. This was beneficial for my sister when a tenant had an underground leak (and pressure loss) with their combi, and after plumber visits, the insurance co. was called in.

    That's kind of you, but I'd imagine that my plumber or associate might have one. However, he did say on Monday that this month-old leak (up to 11 days ago) would have risen to the surface sufficient to detect SOMETHING, even through u/lay and carpet. No signs of damp anywhere, even during the 7 days with no htg and low temp's. Almost impossible to lift carpeting over all remembered pipe runs and the Karndean tiles over mastic substrate in the kitchen/diner/utility are unlikely to allow damp showing through.

    Step by step at the mo'. I phoned Fernox's tech. dept this morning and was told my plan of action was right and to turn off the htg for a few hours just to test, now that the sealant has been fully distributed.. However, it'll only work if there's air on the outside of the pipe/joint (as ANY sealant, I guess). Playing for time here, but they did say that, because a seal is brittle, excess expansion and contraction is not good! This is, i.m.o., what caused the break in the first place.
    Last edited: Jan 26, 2023
    venton and twotone like this.
  17. Mike Reed

    Mike Reed pfm Member

    Revising this thread to update those who have helped or have been interested. However, the thread title is totally inappropriate so I'm starting a new one entitled 'Disastrous and disruptive central heating installation; where to now? Since my last post, considerable monitoring and experimentation has taken place, with mixed results.
    twotone likes this.
  18. mikemusic

    mikemusic pfm Member

    Our guy used a similar product. Forget the name
    He's good and it works for him 95%
    Not for us
    Mike Reed likes this.
  19. palacefan

    palacefan pfm Member

    We had a similar situation years back (must be something to do with Norfolk water?

    Our problem was solved by going over ground and reconnecting into the system leaving the leaking pipe under concrete, worked very well and no destructive and noisy works.
  20. Mike Reed

    Mike Reed pfm Member

    Not so easy in our place, Tony and it has been suggested that the easier way would be to pipe down from upstairs; again, not straighforward and quite disruptive. This still leaves the 2 largish rads htg the kitchen/diner, though, as they're in a single storey conversion. They could, though, as they were newly installed in 2005, be directly accessible and/or have nothing wrong in the pipework.

    Have effectively closed this thread in favour of the other opened yesterday.

Share This Page


  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice