I've always gone with the rule that whenever you move a toilet, you should
replace the gasket. It isn't made of rubber, so it doesn't spring back; it
gets squished when you put the toilet on top of it, and that makes the seal,
but it cannot get re-squished and won't seal properly a second time.

The one time a paperhanger violated that rule (and I was too lazy to pull
the toilet again to do it), I got a leak. Once you have the toilet up,
changing the gasket is cheap and easy (but messy).

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Regards,

Jerry Schwartz
http://www.writebynight.com
e-card JerryS https://ecardfile.com/