Thursday, January 19, 2012

Shabbos problem of using water in high rise buildings

Bnei Brak's Rabbi Moshe Yehuda Leib Landa has warned that turning on faucets in some multi-story apartment buildings leads to the desecration of Shabbat

The rabbi issued a halachic ruling explaining that the using the tap directly turns on an electrical water pumping system – an offense which, according to the Torah, can be punished by stoning. [...]

According to the rabbi, the long-term solution is to install a high water reservoir enabling natural rather than electrical pumping. In the meantime, however, "there is no other choice but to ensure that the pump is turned throughout Shabbat and Jewish holidays."


  1. It's hard to believe that no one has noticed this system and asked a shailoh about it until now.

  2. When I open my refrigerator on shabbos, this has an effect on the electrical system. When I go to the bathroom on shabbos, this also has an effect on the electrical system. When I open my door on a hot shabbos day, this has an effect on the electrical system.

    How is one supposed to live in the modern world if everything you do is violating shabbos by affecting electricity?

    Isn't there a concept of indirect and direct action that comes into play here? Especially, given that the people using the water almost always have no idea where it came from.

  3. Yes, there is a distinction between direct and indirect and subcategories of indirect; delayed and pre-programed actions. I believe the term is 'Grama'. That is basically the concept behind 'Shabbat Mode' to some appliances and light timers.

    Having said that, if you accept the concept of delayed / indirect action being OK on Shabbat and / or Yom Tov, there is no reason not to turn on the hot water tap either. Your direct action only allows the water to flow, all subsequent results / consequences are indirect and delayed.

  4. > How is one supposed to live in the modern world if everything you do is violating shabbos by affecting electricity?

    Aha! Isn't electricity a new innovation and therefore forbidden by the Torah?

  5. I think that up to now, the rabbis confronted the problem by burying the head in the sand (anyway, who would care to think of it), but now it is out in the open...

  6. The definition of "indirect" is complex, mostly because the Talmudic descriptions of it are ambiguous. The more delay, and the more indicrect the linkage of activities, the better. Small delays and/or closer linkages might be a problem, and in fact, having only one or the other (delay or remote linage, instead of both) might also be a problem.

    In the case of a hot water heater, the action may be considered indirect, because you are not directly drawing cold water into teh heater, nor turning up the fire/current heating it. You are RELEASING the valve that previously stopped water from running out of your faucet. The water pressure behind the talk is then what forces cold water into the talk (and about the same amount of water out of your tap). There is only one indirect link, or possibly two, so it isn't the strongest grama for "indirectness." However, worse, there is zero delay. The very moment you open your tap, the pressure immediately forces new water into the system, which then gets "cooked" (heated) in the talk, even if there is no current flame or electricity applied to teh talk -- the water already in the tank is almost always hot enough to cause halachic "cooking."

    A separate issue is whether the heat will turn on. There, you are on firmer ground. The linkage is very indirect -- after the cold water comes in, it must then convect with the hot water, until the temperature around the thermostat sensor is lowered to the point that the thermostat activates. That in turn sets a series of mechanical and/or electronic events to close relays or open a gas valve. The heating elements then have to warm cooking temperature, or teh gas has to ignite via the pilot.

    Some rabbis have approved the "ShabHot" system, which is essentially a programmable thermostat for a water heater. It is set to a temperature too low to be considered halachic cooking, and also has a delay built in. The result is that you get WARM water on Shabbos. A big downside: it would have to kick in the lower temperature setting long before Shabbos, so that the water has a chance to cool before Shabbos starts. Otherwise, ten minutes into Shabbos, you would still not be allowed to turn on the hot tap without violating Shabbos (because the cold water still immediately rushes in to the still-hot water, with a somewhat direct action on your part). That means pretty cool showers for teh last, say, few hours before Shabbos. [One could set it to keep hot water until right up to Shabbos, and then refrain from using hot water until one is certain that it has cooled sufficiently. But how would you know when that is? And how likely are you to make a mistake?)

  7. As to cold water pumps, it depends on engineering. Most systems are designed so you don't have to have to build a pump large enough to keep up with peak demand. Instead, build a tank atop the building with capacity to supply peak demand for some reasonable period, and a slower refill pump.

    For example, take a 12-storey building with peak demand of 1000 liters/hour, peak periods of 6a-8a, 7p-9p, and three hour leading into Shabbos. The longest peak is three hours (Friday), using 3000 liters. A 1000 liter/hour pump with 50 meter headroom would be very expensive. A 3000/liter tank on the roof is adequate, but you will occasionally have a higher peak, and need some room for growth. A 3500 liter tank is a good choice. Cross check that against the short non-peak interval -- 8a-7p - and ensure it could refill in that period: a 250 liter/hour pump will fill the empty tank in 12 hours; since it will also be filling the tank a but during the peak period, that should be sufficient.

    What causes the pump to activate? Startup cycles cause most of the wear on mechanicals, so you don't want it constantly starting and stopping during non-peak periods. Instead, you set the tank to allow a certain amount of water to drain before it requests refill... say, 10% (350 liters).

    That's the final key fact for halachic evaluation. If the tank won't refill at all for the first 350 liters, then here's what will happen over Shabbos:

    Tank is mostly empty (post-Friday peak) to start, about 2500 liters to refill. Pump runs continuously for about ten hours. During that time you then have no concern about using the water, because the pump runs anyway (your use is a grama that extends the stop time, generally considered OK). Pump finally stops, you still have no concern: It won't re-activate until another 350 liters are used. Since nobody is bathing on Shabbos (in a mostly-religious building), you may not even have the pump turn on at all until after Shabbos. Even if it does, ***NO SINGLE USE HAS ANY SIGNIFICANT LIKELIHOOD OF BEING THE ACTIVATING EVENT.*** The pump will go through maybe 3 power cycles across the whole Shabbos? There are probably hundreds of faucet uses during that period. Each use has less than 2% chance of precipitating refill. Further, whichever faucet use activates the pump may only cause the activation after a minute or two of use; the chances of the activating event being within the first few seconds is also relatively small. In addition, there may be other faucets active at the same time. So it becomes a safek event (<2% chance), possibly a "shared" event (adds romm for leniency), with a safek (but likely) grama if it were to be the precipitating event, on a rabbinical melacha.

    Sounds OK.

    Why is it suddenly a problem for Rabbi Landa? A few possibilities:

    1) this was the first time the question was brought to him, and he issued his statement (not a p'sak!) as a notification while he examines it

    2) some buildings may have been inadequately planned or planned with incorrect assumptions, causing a more frequent refill cycle

    3) some buildings parameters may have changed over time (denser population has same effect as the latter)

    4) newer systems may be more efficient, and better planned, allowing lower flow pumps that activate more frequently

    5) there may be some systems that primarily use ambient water pressure, but are marginal for the upper floors. Such buildings, if they only have a small demand per floor (think single-apartment penthouse) may use an instant-activation pump to boost pressure only for the low-pressure floor(s), which would indeed be a problem.


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