Weishan's "Musings on Modern Planescape" made me think of this. I figure the most common source for water in Sigil is the Elemental Plane of Water, but how do you get that water to each and every inhabitant?
I think I recall a fountain or two being mentioned in the PS source material, but if Sigil's population is at all large, an aqueduct system of some kind seems much more likely.
There's also the ditch 
:)
I'd assume there would pe portals in various locations in addition to maybe larger underground reservoirs (I don't know if they wer mentioned in cannon, but it's a sound idea, that adresses logical issues without using a few knocked over decanters of endless water).
On Zim'squestion on Sigil's population, is a quarter million according to the 3.5 planar handbook. 2e cannon puts the figure a bit larger (I'm not going to look right now). I put the population higher, but that's irrelevant.
Weishan's "Musings on Modern Planescape" made me think of this. I figure the most common source for water in Sigil is the Elemental Plane of Water, but how do you get that water to each and every inhabitant?
I think I recall a fountain or two being mentioned in the PS source material, but if Sigil's population is at all large, an aqueduct system of some kind seems much more likely.
I believe the thinking was that there there were doors open to each of the Elemental Planes to provide some purity and freshness to each of the elements in the city, and there was a reservoir underneath the town guarded by the dabus and other, more dangerous beings to protect the sanctity of the city's water - the thinking being that anyone who managed to take control of the water would have significant control of the city, and thus too dangerous for anyone but the Lady or her direct minions to oversee.