[Avodah] If you have an electronic water meter, can you turn on your faucet on Shabbos?

[Micha Berger]

On Wed, Jul 18, 2012 at 02:28:33PM +0300, Marty Bluke wrote:
: In an interesting letter in yesterday's Yated Neeman a writer brought up
: this issue. He claimed that in some places in Israel they have installed
: electronic water meters and therefore you can't use the water on Shabbos....

Pesiq reishei delo nicha lei -- PRDNL.

 From notes on an essay "Motion Sensors and the Concept of P'sik Reishei"
by R' Josh Flug, here is what he has on the subject -- sorry, no mar'eh
meqomos (I don't have the back page[s] with the footnotes.)

The Arukh holds it's mutar.

Tosafos hold it's assur derabbanan, as a kind of melakhah she'einah tzerkhah
legufah.

The SA holds like Tosafos.

The Terumas haDeshen allows pesiq reishei delo nicha lei when the issur is
derabbanan.

The MA does not.

R' YE Spektor is meiqil like the Terumas haDeshen.

The MB holds like the MA, but does allow a double-derabbanan. Eg:
Closing a large box that has a bug of a sort not normally trapped
inside. Derabbanan 1: the box is large, so the bug still needs to
be cornered within the box if you wanted to hold it. Derabbanan 2:
it's not normally trapped. So, PRDNL would be mutar in this case.

Similarly, the more practical case of eating a cake that has lettering
on it.
Derabbanan 1: Mechilqah shelo al menas likhto
Derabbanan 2: Derekh achilah
So, PRDNL is permitted.

(Lately the local bakery is more machmir than the Rama and the MB,
and puts the frosting on a card which one can remove before cutting
the cake.)

ROY only requires one derabbanan.

Now the question is whether the water meter (or the motion sensor)
does anything that if done straightforwardly would be assur deoraisa.
Then you can ask your LOR if he holds like the Terumas haDeshen (and
RYES and ROY) or like the MA (and MB).

Tir'u baTov!
-Micha

-- 
Micha Berger             We are what we repeatedly do.
micha at aishdas.org        Thus excellence is not an event,
http://www.aishdas.org   but a habit.
Fax: (270) 514-1507                   - Aristotle