I have a small leak on the thread of my bath waste connection. This leak is inaccessable without ripping out most of the bathroom. Is there anything on the market that works like radweld in a car that I can add to the bathwater that will seal the leak without destroying my bathroom?
No there isn't, unfortunately - if you really can't access the waste the only thing you can do is to unscrew the plastic nut on the water trap, plaster the threads with silicone sealant and hope for the best. Ideally the waste outlet or water trap has to come off to be successful, in my experience.
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