Expanding foam and water pipes

Discussion in 'Plumbers' Talk' started by msmx, Nov 21, 2017.

  1. msmx

    msmx New Member


    Apologies if this is a stupid question, I'm not a tradesman....

    I need to fill in gaps underneath a fitted corner bath due to cluster flies gaining access through the cavity wall. I've looked underneath the bath and can see quite large gaps in the plaster behind the copper hot and cold water pipes, along with some gaps where the floor meets the wall.

    The only solution I can see to this is to use expanding foam with an applicator gun to fill in these gaps. I have spoken to the plumber who fitted the bathroom and he has suggested that to remove the bath may cause damage as he has fitted it securely with silicone etc and would be reluctant to try and remove it in case of damage to the edge of the bath and the tiles. It's an hydrotherapy bath so not cheap to replace should it get damaged and this also means there is lots of extra 'stuff' going on in the space underneath the bath.

    I have looked online and keep seeing things saying that expanding foam shouldn't be used near copper pipes, however the articles/threads are years old so I was wondering if things have progressed in that time and if expanding foam and copper pipes have made kissed and made up or if I need a plan B?
  2. I can't think of any reason why this cannot be done.

    It certainly won't cause any issues with the copper, so don't worry about that. Possibly the heat from the hot pipe will degrade the (some) foam immediately in contact with it, but actually I think even that is very unlikely. (A hot 'cylinder' is effectively a big copper tank covered in exp foam!)

    Folks on here will recommend a good product, I am sure. Then, literally, fire away.
  3. seen it all before

    seen it all before Active Member

    Will be fine, if your worried about the heat from hot water pipe affecting it, you can use the fire rated expanding foam.
    It will be slightly dearer but give you a bit more piece of mind.
    Thus would be available from screwfix I'm sure.
    CGN and Deleted member 33931 like this.
  4. msmx

    msmx New Member

    Thanks for the replies....

    The threads I'd seen from years back claimed that expanding foam and copper didn't go together and there was a risk of corrosion if it came into contact with the pipes. Is this not the case?
  5. No. I can't think of any way that this could happen.
    msmx likes this.
  6. seen it all before

    seen it all before Active Member

    No corrosion whatsoever. Carry on.
    msmx likes this.
  7. msmx

    msmx New Member

    Brilliant, thanks you two :)
    Deleted member 33931 likes this.
  8. Mattandlyn

    Mattandlyn New Member

    Lots of disagreement on this issue. Some say 'no', some say 'yes', some say heat can deteriorate the foam. There is every conceivable contradiction you can think of out there.
    I'm just redoing some house renovations and I've uncovered work I done around 30 years ago when such issues weren't a problem because there was less choice and no interweb from which to seek advice! I filled areas around central heating pipes with expanding foam, in some cases excessively due to my lack of skill at that time. Pulling it apart now the copper was totally intact but areas of foam around the pipe showed some effects from the heat I guess, looking like melted crunchy bar honeycomb. it was minor and the radiators have been working fine all that time. The foam was around and in contact with soldered joints as well as copper pipe also plasterboard, wood and plastic. So I would guess, with no problems after 30 years, expanding foam does not react with copper pipe!

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