There are sewer tanks where, when full, an electric sewer pump automatically turns on.

Is it a problem to pour water down the drain (washing hands, flushing the toilet) into such a sewer system?

One is not directly causing the pump to turn on -- it only kicks in if the tank becomes full.


Rav Aryeh Leibowitz quotes the Nishmas Shabbos (6:75 - note this teshuva doesn't seem to be the correct address) saying that if the electric sewer pump will only be activated after a few flushes, then it may only be considered a grama since it's a ko'ach sheni. Nonetheless, if you can pour the water out upstairs then it is better to do that, while it may be uncomfortable for a guest in the basement to go upstairs. He also notes that is would be better to wash your hands with the faucet rather than a utensil since using a utensil would be pouring the water directly into the container while just opening the pipe is less direct. He also notes that it's a safek psik reisha which might be considered a davar she'eino miskaven, so there is more room to be lenient. Rav Leibowitz concludes saying that many poskim are lenient with a commercial tank which holds more than one flush, though it's better to use an alternative bathroom if it's not uncomfortable.

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  • That's what I heard when a shul renovated recently -- get a commercial system so that no one flush will definitively trigger it. – Shalom May 26 at 15:53
  • After doing some research it seems like it is in an addendum to Vol 6 #75. However unable to find the addendum online. – Gershon Gold May 27 at 2:32

Rabbi Meir Aaron who operates Halacha.CO who is a Chabad Rabbi, says it is permitted for the following reasons.

1 - It does not turn on specifically after each flush.

2 - Kovod HaBriyos is permitted when the prohibition is Rabinnic in nature.

See here for the entire answer and sources.

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