I've just fitted new taps to the bath, and have a couple of compression joints that are leaking a little. I know Boss White is not to be used on potable water, but does this run to water used for Baths etc?
Young kids love to drink bathwater (amongst other things) so I wouldn't like to contaminate it wilfully. Why not just wrap a few turns of PTFE tape around the thread, that usually works.
Pp down to your friendly local plumbers merchant and ask for a packet of 'orses air', or as its properly known, plumbers hemp. A small strand of that round the compression thread and your leak will be sealed. Also, I wouldn't be at all concerned about using plumbers mait on the bath waste etc, there shouldn' be any sealant showing anyway,because you will have carefully scraped away the excess, won't you. cheers, pete