How long can I leave a CH system empty of water?

Discussion in 'Plumbing and Central Heating' started by Tubbsup, 26 Nov 2021.

  1. Tubbsup

    Tubbsup

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    Hello everyone,

    I have one main question. And I have extra details below if anyone wants more information.

    Is a drained down, empty CH system more corrosive to the insides of the pipes, rads, boiler, etc, than a system that's full of water?

    I haven't been able to as yet get a new boiler installed. The boiler I have is a 26 year old Maxol. And there's a small tank in the loft. If the boiler breaks down, and it's too expensive to fix, and if I then drain down the system to avoid the pipes bursting, how long can I allow the system to be empty of water before it needs to be filled again? Or should I do the refill once the winter has passed?
    It maybe some time before I get another heating system installed.

    I'll appreciate all answers given.

    Thank you

    Paul
     
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  3. Madrab

    Madrab

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    The issue with leaving a previously used system drained down and empty is that the inside of the rads will rust. How much depends on how long they take to dry out I guess. The system will need cleaned and flushed properly prior to re-commissioning.
     
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  4. Tubbsup

    Tubbsup

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    Thank you Rob for your reply.

    Following on from the above and my concern with a boiler failure and the pipes freezing, would the rads rust that much if I drained down the system and left empty for a couple of months, then refilled, but the cleaning and flushing would actually be done eventually when a plumber puts in the new CH system some time later?

    I'm just trying to see if I can last out this present winter, if the boiler does fail, but I'm unable to put in a new CH system over this particular winter.
     
  5. Madrab

    Madrab

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    They will rust a certain amount until all internal moisture is used up, how much that would be is not an easy question to answer unfortunately.
     
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  6. Schrayder

    Schrayder

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    Be plenty of water in pipes, even when it seems empty, fill er up and bung in some inhibitor should only take a few minutes.
     
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  7. Madrab

    Madrab

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    If the system is drained properly then most of the pipework should be empty? Unless it's been piped up badly and there's low spots etc of course. Even then though, luckily, the pipes won't rust.

    The rads, if emptied, will always rust somewhat. When the system is filled that can then go into solution and be transported around the system and end up where it can cause problems longer term. To avoid this the system needs cleaned and flushed when lying empty for a while.
     
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  8. Schrayder

    Schrayder

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    Imo there's generally going to be enough water in those low spots with nowhere to go to cause plenty of rusting
     
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  9. Harry Bloomfield

    Harry Bloomfield

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    Could you not buy and add to anti-freeze to the system, if it does fail? You would just need to leave the boiler in place, drawn some water to make space for it, top up and run the circulation pump to distribute it throughout the system. X500 is an anti-freeze for CH systems.
     
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  11. Tubbsup

    Tubbsup

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    Many, many thanks for all the replies.

    Cheers Schrayder.

    Rob, the potential rust going round the system later on sounds a very valid concern.

    Following on from Harry's point , would it be best to put in inhibitor now whilst the boiler's working, then I wouldn't need to drain down at all, and hope for the best over the winter if the boiler does fail? Moreover, can the pump still be worked if the boiler fails, if I add inhibitor then.

    Saying that, I was in the loft earlier today and found lying by the small tank one container of KAMCO Systemsafe-DM Professional, and one container of Sentinel X100. These would have been put in prior to my arrival 9 years ago. I haven't actually used the CH full on over the years, which may make a difference? Or should I now just add another load of X500? Does it matter if there's different inhibitor liquid within the sytem?

    Thank you in advance for your advice.
     
  12. Harry Bloomfield

    Harry Bloomfield

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    Take your advice from the experts in the forum, but some say it's fine to mix, others say don't mix - over time it will be diluted, so best to assume it has none it at all.
     
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  13. Tubbsup

    Tubbsup

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    Thanks Harry.

    That's a good assumption to accept the sytem now has no or little inhibitor in it.

    A question I have is: if I put in X500 inhibitor would that provide sufficient protection against freezing over the winter, if the boiler does fail?
     
  14. Harry Bloomfield

    Harry Bloomfield

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    A question you need to answer, is will this place be left with no heating at all - that makes a great deal of difference to how much protection might be needed. A car cooling system may need 25% anti-freeze, to 75% water to ensure protection. The X500 makers instructions will detail the amount needed, for what level of protection. Where is the F&E tank located, is that and the pipework up there insulated? That location will often be the area which suffers most in a cold snap.
     
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  15. Madrab

    Madrab

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    Don't forget to add to that whether the pipework is lagged/insulated? If not, that may be an idea too regardless of how the system is left, that would extend the time it takes for the pipes to freeze.
     
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  16. Tubbsup

    Tubbsup

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    First of all, many, many thanks for your comments. They are very much appreciated.

    To respond: the F&E tank is in the loft, and has lagging around it.

    With my CH system, as I can work out: The rad pipes run in/are embedded in the thick internal, insulated wall panels. Then they run in the floor, for the upstairs rads, and the ceiling, for the downstrairs rads, to the boiler. There are no pipes in the loft. The house is fairly modern at 26 years.

    The added conservatory rad is an issue. The pipes for it come off the dining room rad, through the external wall, and around 2 walls in the conservatory, in empty white runking, at a distance of about 4 meters. The conservatory does freeze over the winter. A thin film of ice appears in a small tub of water I leave next to the rad each year, plus there's a thermometer, to tell me what the temperature is doing..

    The obvious question is: should i remove the trunking and put lagging around the conservatory pipes?

    Overall, all the above I've written in the hope that I don't have to drain down and refill, and if freezing is unlikely then I don't need to?

    Once again, I will appreciate your advice.
     
  17. Harry Bloomfield

    Harry Bloomfield

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    Any measures you can take to try to prevent freezing in that the coldest area, will help. I wonder though if some expanding foam might provide better insulation though (for comment!).
     
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