Dear Rabbi Simon.
I wanted to consult with you about the halakhic aspects of something. At the synagogue of which I am the chairman we are due to replace a tap in the toilet. I am concerned that the current proposal of a single mixer tap is not a good idea as it would mix potentially hot/cold water, activate the boiler that is required for heating, etc. I assume that a single tap with two levers would be OK. Any suggestions? I am happy to discuss if it is a nuanced answer.
TY for your practical question.
You are definitely correct that two levers is the way to go. A single lever can very easily lead to inadvertent Shabbat desecration if it is not carefully moved fully to the right every time, to utilise only cold water. A public building such as a shul should not rely on the astuteness (not to mention Shabbat observance) of every user (children and adults alike) to avoid utilising the hot water, which (as a rule) is definitely not allowed on Shabbat. (Note that I am not saying that such a tap should be avoided in one’s home. But it is not appropriate for a public location used on Shabbat.)
Rabbi Rashi Simon