Pressurization of Building Storm Drain Piping.. Easy Question..
Pressurization of Building Storm Drain Piping.. Easy Question..
(OP)
Hello Everyone,
I am not an expert on this subject, just interested, and I have a question which I am not exactly sure how to Google. I wanted to throw out what I think should be an easy question to people in the field in hopes that I could get some information on where to look for additional learning materials.
I noticed in a building recently that the building has storm drains which carry rain water from the roof, into the city storm system. The drain pipes are all iron, and are connected with rubber MJ couplings. To me, this type of connection cannot not handle any pressure within the pipe, and normally it does not need to since normally drain pipes are not full of water. However, what happens in a larger rain storm situation where we have a lot of water entering the city storm system. I can imagine a situation where the storm pipes from a building will not be able to purge quickly enough into the city's storm system and the water level within the buildings storm drain will rise. If we begin to fill the storm pipe within a building at a higher rate then it can discharge into the city, the storm drain will begin to fill up.
If a storm drain is filled with water 4-5 stories high, would we not start to pressurize the storm drain pipe (simply due to water head)? I've yet to see a storm drain pipe that can withstand much (if any) pressure. Would such pressurization lead to drainage pipe failure and cause rain water to flow into the building?
Is my above scenario realistic? Do situations occur where storm pipes are completely filled up? What sort of solutions are buildings equipped with to prevent such failures?
Any information on the above would be greatly appreciated,
Thanks in advance!
I am not an expert on this subject, just interested, and I have a question which I am not exactly sure how to Google. I wanted to throw out what I think should be an easy question to people in the field in hopes that I could get some information on where to look for additional learning materials.
I noticed in a building recently that the building has storm drains which carry rain water from the roof, into the city storm system. The drain pipes are all iron, and are connected with rubber MJ couplings. To me, this type of connection cannot not handle any pressure within the pipe, and normally it does not need to since normally drain pipes are not full of water. However, what happens in a larger rain storm situation where we have a lot of water entering the city storm system. I can imagine a situation where the storm pipes from a building will not be able to purge quickly enough into the city's storm system and the water level within the buildings storm drain will rise. If we begin to fill the storm pipe within a building at a higher rate then it can discharge into the city, the storm drain will begin to fill up.
If a storm drain is filled with water 4-5 stories high, would we not start to pressurize the storm drain pipe (simply due to water head)? I've yet to see a storm drain pipe that can withstand much (if any) pressure. Would such pressurization lead to drainage pipe failure and cause rain water to flow into the building?
Is my above scenario realistic? Do situations occur where storm pipes are completely filled up? What sort of solutions are buildings equipped with to prevent such failures?
Any information on the above would be greatly appreciated,
Thanks in advance!





RE: Pressurization of Building Storm Drain Piping.. Easy Question..
Might be site/condition specific.
RE: Pressurization of Building Storm Drain Piping.. Easy Question..
Peter Smart
HydroCAD Software
www.hydrocad.net
RE: Pressurization of Building Storm Drain Piping.. Easy Question..
RE: Pressurization of Building Storm Drain Piping.. Easy Question..
I'd have to go back and re-analyze to check for sure, but my gut feeling is that the 100 year peak discharge was controlled down to around 10 year levels by the roof, which I think is pretty close to building code anyway. I'm not an MEP, can't speak to those specifics. So my gut tells me that the building codes, which point to a lower design storm, in fact handle the 100 year storm quite nicely given the entrance restrictions commonly seen on buildings.
That makes a kind of sense, as you'd think if pressure flow for event storms was a problem, that the MEP codes would have adjusted to match. Seems to me that the code writers got this right, if not exactly for the reasons they thought they did.
Keep in mind, the design storm intensity for these systems is based on a very low Tc, so even if it did leak it wouldn't be leaking for long.
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com