Two Sinks, Two Microwaves... Two Toilets?

Q. Hello. If a household had two toilets, one for [liquid waste] and the other for [solid waste] and the two waste materials were flushed down separate pipes and not combined until after Sabbath, would that be approved under Jewish law? What if the toilet also automatically flushed every 30 minutes so no mechanical action had to be performed?

A. I think the question is, why would a family have one toilet for liquid waste and another for solid waste? Even if one had a urinal in one’s home (which I've never seen), why would anyone restrict a toilet to solid waste only? Additionally, since one may flush a toilet on Shabbos, why would one feel the need to put a timer on one?

In short, these seem like fixes for a problem that doesn't exist. Can you please explain to me the perceived need for such things?

Q. I read an article that flushing a toilet on Sabbath is prohibited because of the mixing of substances. If I was to build Sabbath-friendly apartment high rises in my region, I wanted to find a solution to this rule for convenience, as well as hygiene, to be acceptable for Sabbath-observant Jews.

The article mentions a prohibition on coloring substances. Perhaps only the ultra-Orthodox Jews have this rule? Or is it the rule for all denominations of Jews?

A. Generally speaking, flushing a toilet poses no Sabbath-observance problems whatsoever, with the exception of electric devices such as motion-detector flushes and underground toilets with electric pumps. The article you reference addresses toilet-cleaning discs, which color the water blue. This is an optional add-on that most people don't have, and such a thing is not necessary for operating a toilet.

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