todays lesson has been “Expanding foam corrodes copper pipe”.
You have been warned 🙁

Repair was on a pipe that ran along the top of ceiling joists (single storey so cold a breezy up the roofspace) and then turned 90 deg down through the ceiling into the downstairs cloakroom.
When we moved in 13 years ago I decided I didn’t like the cold draught coming down the hole in the ceiling that the H&C water pipes used – so I squirted expanding foam around the pipes in the roofspace to seal the hole.
The leak today was under the foam and when I repaired it I found a couple of other points where the water was seeming through the pipe – must have been caused by the foam as the pipework is only 30 years old. Was trickier to fix than I’d anticipated but I think we’re there now.

Thankfully I’ve not used expanding foam anywhere else!

i was always told to use denso tape round copper pipes when using expanding foam near……..

that was when i was mouse proofing the entry for my heating pipe work into the cavity under the floor – denso round the pipe , steel wool in the gaps – expanding foam in the rest.