If I were to connect a standard sized copper pipe to the Baltimore City water that comes into my house, and run that pipe straight up in the air, how tall would it have to be before the water pressure isn’t sufficient to make the water spill out the top?
You need to know the water pressure that the city is delivering.
It varies all over the place 30-120psi or more.
If it was 60 psi, that would be 1662 inches of water.
I think I read somewhere, maybe xkcd, that most water pressure is good for about 4 or so stories? I’ll go see if I can find that xkcd.
Edit: hereit is. 40meters.:smack:
Baltimore’s water comes from three reservoirs: Pretty Boy, Loch Raven, and Liberty. Pretty Boy and Liberty are something like 400 to 500 feet or so above sea level. Loch Raven is a bit lower, something like 200 feet. I believe all of Baltimore’s water is gravity fed. It’s not pumped.
Even though I lived in Baltimore for a while, I don’t actually know how the entire water system is structured, so I don’t know if the water system is all interconnected or if each reservoir serves a particular part of Baltimore (city and county).
If you are down near the Harbor, the elevation there is basically sea level, so, assuming all of the city’s water is interconnected (maybe not a valid assumption) your pipe would have to be over 500 feet tall before the water flow stopped. On the other hand, if you are out on the northwestern side of the city where the elevation is the highest, you are pretty close to the reservoir heights and your pipe may only need to be maybe a couple dozen feet tall.
500 feet is 200+ psi, and I doubt that any city is delivering water at that pressure.
They would be having leaks all over the place.
If your water tank is 500ft above sea level and you are sitting at sea level, wouldn’t you have to get the pipe at least 500ft up before the water stopped leaking out?
They do have leaks all over the place. 
It may be that the higher elevation reservoirs serve the higher elevation areas of the city. Like I said, I don’t know how the water system is structured.
Yes, if there were no pressure regulators in the system.
I live in North Baltimore, actually about 2 blocks into the county, probably about 3 miles from the Loch Raven dam.
I’d imagine though that water pressure is artificially kept fairly uniform. I’ve lived all over Baltimore county and haven’t noticed the water pressure being any different in other areas.
Going back to the OP’s question:
Pressure and water column height have a directly proportional relationship:
P = rho * g * h
P = water pressure
rho = water density
g = gravitational acceleration
h = height of water column
In fact, “inches of water” and “feet of water” are both actual units of measurement of water pressure:
1 psi = 27.7076 inches of water
So if you know your supply pressure, you can calculate the height of the water column you could produce with an open-top pipe. Beowulff nailed it in the first response.
No city is supplying water pressure at 500 feet. There are pressure-reducing valves and intermediary tanks as necessary to keep things relatively consistent 40-60psi in the vast majority of cases. Excess pressure is a great way to destroy your delicate plumbing fixtures.
And there may be US cities that supply drinking water directly from open-air reservoirs, but Baltimore is not one of them. The water from the three reservoirs flows to several water treatment plants; the treated water is pumped to where it is needed.
The PSI answer is correct. However, I thought the simplest answer is “approximately the height of your nearest water tower”
If there are no pressure regulators between you and that tower.
Apparently the height of a “standard” water tower (from its top to its own base, not to your local elevation) is generally about 130 feet, so this actually is a pretty reasonable measure.
Just to add:
Pretty Boy flows into Lock Raven and is piped down to Lake Montebello. There is a filtration plant there that makes it potable.
Liberty is piped down to the Ashburton WFP which is near Druid Hill Park, where it is treated. Both serve the city.
Baltimore City also takes water out of the Susquehanna. That water is pumped into Montebello from the Winter’s Run PS near the Conowingo Dam.