I always keep a bar on this stuff on hand. Just this last week I patched a corrosion pinhole in the water line on my pool heat pump. It was a copper pipe, filled with chlorinated water at 20 psi, so it wasn't a simple problem to fix. And it was on the bottom of a pipe inside a heat pump with limited bottom clearance, so I did the job standing on my head. But if you rough up the surface and make it super clean (with acetone if possible) and wrap it all the way around, it will patch the hole. Cure overnight for full strength and now I don't have to pay $5000 for another heat pump. I had the same problem on the input line 2 years ago and the first EP-400 patch I put on that side back then is STILL leak free.