The PS Campaign Setting ...
... is not the topic of this thread.
I'm not trying to be rude here. But we're discussing Sigil
as described in the 4E Manual of the Planes. Not how it used to be. Maybe the terminology and portal types you describe will be revived in DMG II or some other book, but at the moment they're just not relevant.
They wrote themselves into a corner on this one in 4e, because they omitted any mention of the Gatetowns and their permenant portals to Sigil.
It needs to be asked though: was it omission by accident (or word count) or by design? The Gatetowns make access to Sigil fairly safe and predictable. Maybe the 4E devs made a conscious decision to make Sigil hard to get to and hard to leave. They may have written themselves into a corner, but perhaps it's exactly the corner they want to be in.
You have trash, you dump it through any random portal you can get away with as long as someone from the other side doesn't walk through and bash your skull in. Random, periodic portals not next to your kip are probably a good choice.
That could work. Any portal to the Elemental Chaos is essentially an incinerator. Of course, if you empty your chamber pot on an Efreeti's head he would probably get cranky.
I sort of like the idea though of the sewer system being just thick with gelatinous cubes, carrion crawlers and similar "recyclers".
Plus, you could have a colony of ghouls that feed off the corpses that come floating down the sewer-ways, and if the PCs killed the ghouls some authority figure (not the Lady of Pain though) might try to fine them for "Contributing to the befoulment of Sigil's water system."
It rains. All. The. Time.
The city has its own weather system, though it's up for debate if it's entirely natural, or a magical property of the city itself, or if it's a result of portals opening up to draw in moisture, etc.
Not so much any more. Here's the new money quote on that topic:
Manual of the Planes said:
Sigil doesn’t have much of an environment ... It never gets extremely hot or extremely cold, it has no monsoons or tornados, and what does pass for weather just tends to make everything look gray and dingy. ... the inhabitants don’t have to worry about their houses surviving the next big storm ...
Sounds like there's a permanent fog or gloom, but not rain per se. Thematically I prefer a bit more variety, just so I have something to describe to my players, but that would be a "house rule" not the canon.
Ergo, you need a source of liquid water. Rain barrels won't get you anything. That's why I suggested massive cisterns beneath the streets that capture and recycle the waste water from the city. The cisterns could then be accessed via private pumps (in palaces, fine Inns and temples) or public wells (everywhere else).
The Hive is packed to the gills in total squalor (except for the Slags which... well... the Kadyx lives there). The Lower Ward is fairly dense. The Lady's Ward (and especially some districts therein) is pretty light.
To make the Hive "packed to the gills" you'd need to assume that The Lady's Ward or the Clerk's Ward are completely deserted.
But that's really neither here nor there; the main thrust of my comment on this point was directed at how how Wizards (regularly) throws out numbers without doing any checksums for "common sense" rationality. This is hardly unique to the Sigil description; you can find plenty of threads complaining about stuff like this. Wizard's propensity for handing out maps of towns with 15 buildings (and a population 350) is comic legend. This is the same problem, just in reverse. Using the numbers given by Wizards results in a Sigil with the population density of a 1/2 acre plot suburban McMansion development. Sigil either needs to be a lot smaller or the population quite a bit higher than 250,000 (I prefer the latter solution).
I did find an error in my math though. The proper area of Sigil in square miles is 72.5415923, which is equal to 187.881862 km^2. With a p of 250,000 that results in a population density of 1,330.6 p/km^2. That's still sort of sparse though, if you compare it with the cities given on my list. Even given population density disparity between Wards, you'd have to depopulate the "nice" Wards to the point of making them ghost towns to get the Lower Ward or Hive anywhere close to the building density pictured in the book.
Just by comparison, Sigil (by land area) is roughly the same size as Kolkata (which you probably know as "Calcutta"), but has just 1/20th (or 5%) of Kolkata's population. When I picture Sigil I imagine density on par with Kolkata as it more or less actually is, not 1/20th as dense. I would bump the population figure by 10x (minimum).
And for your calculations, the torus isn't closed, and the city's dimensions are not stable. It shrinks and grows at The Lady's whimsy ...
Not any more. The torus is closed and the dimensions are given on MotP pg. 27. There is no mention of the numbers changing.
Torus diameter (from outer wall to opposite outer wall): approx 6.4 miles.
Tube diameter (from street level to "directly above" street level): approx 1.5 miles.
Circumference (outer wall): approx 20 miles.
Surface Area of a Torus = A*C*4*pi^2, Where
A = Radius of the tube (i.e., 0.75 miles)
C = Radius from the center of the hole to the center of the torus tube (i.e., 2.45 miles)
Random Thought: In Sigil, you really do have to walk uphill in both directions.
