In article , Jeff Wisnia wrote:

At the risk of asking a really dumb question.....Is something akin to an
automotive cooling system "stop leak" product ever put into a hydronic
heating system to plug a small leak (maybe as just a stopgap "fix")
without screwing up something else in the system?

No. Stuff like that can prevent valves from seating properly.

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Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.