Note: The letter was written on stationery of HaRav Nissim Karelitz and signed by him and other poskim and rabbonim.
20 Kislev 5772
Since there is an installation of special Shabbos equipment for water pumps in apartment buildings, in which a person has no effect whatsoever through his or her opening and closing a faucet on turning on or off the pumps. It is a preferred arrangement with no chashash.
In contrast, there are other installations in which there the person's actions have an effect on the turning on or off the pumps. This has a chashash of stumbling blocks of chilul Shabbos chas vesholom.
Therefore, it is obligatory to use the arrangement that has no chashash. Further details are available at Mishmeres Shabbos, tel: 0722 164422.
I also join the above.
Y. S. Eliashiv