@doctorcrypto I've had a close look at the coating on the pool, I'm not sure if its chlor rubber or two pack or just a waterproofing membrane, but it is letting go of the substrate. Its really drummy (I'm not sure if that's a term you use where you live, but essentially it is delaminating ) and it has holes all through it. I am going to have to grind it all off and probably start again if I want a good finish on it. I suppose initially I could patch it to get it working as a pool again, but in the long run, i will have to address the whole coating. I am told that the pump and filter all operate properly. So that is one good thing!