I posted a few days ago about electronic water meters and can they be used on Shabbos.
A number of people suggested that this should be permitted because it is
a פסיק רישיה דלא ניחא ליה on an איסור דרבנן. I would like to
raise 2 issues with that premise:
1. Is this really לא ניחא ליה?
Everyone would agree that you cannot disconnect the meter before
shabbos and use the water because you would be stealing from the water
company. Therefore, the meter recording how much water you used is ניחא ליה. If the meter didn't record your use the company would not be able
to charge you and you wouldn't know how much to pay, in essence you
would be stealing. Therefore, you want the meter to record your use to
keep you from stealing.
2. It is not so clear that פסיק רישיה דלא ניחא ליה on an איסור דרבנן is permitted. R' Eider in his sefer on hilchos shabbos writes
that a פסיק רישיה דלא ניחא ליה on an איסור דרבנן is assur. The
Shemiras Shabbos in the new edition has an introduction to Hilchos
Shabbos. In the text he doesn't discuss פסיק רישיה דלא ניחא ליה on an איסור דרבנן but in a footnote he quotes a number of Mishna
Berura's that it is assur. R' Willig in his sefer Am Mordechai on
Shabbos, wanted to make the following distinction by פסיק רישיה דלא ניחא ליה on an איסור דרבנן. He said that if the issur is עיקרו מן התורה and it is only דרבנן for a technicality (מלאכה שאין צריכה לגופה ,מקלקל, etc.) then פסיק רישיה דלא ניחא ליה
on an איסור דרבנן would be assur. But if the issur is עיקרו מדרבנן like electricity then פסיק רישיה דלא ניחא ליה would be
mutar.
