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we have an internal roof drainage system on a 1880 small condo building in New England (MA) that goes to the sewer drain pipe. I just cleaned the outlet for the first time since we moved in. I am pretty sure it has not been done for many many years. So a couple of questions:

  1. After some research, my understanding is that the roof drain should be separate from the waste water sewer. This might differ by state but what are the regulations about this? I know that the roof was redone at some point (less than 10 years ago, I think). The accessible part of the cast iron pipe was also replaced with PVC (basement and attic, the rest is still cast iron). At what point do old buildings have to separate the storm drainage from the waste water sewer?
  2. Is standing water an issue? The roof generally slopes towards the central roof drain but there is one spot with standing water (see highlighted part in 2nd picture). Is that an issue?

Thanks!

Before cleaning enter image description here

After cleaning enter image description here

Roof drain enter image description here

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    Your local town/city will have the best answers. While most places do not allow storm hook ups to sewers now, some do. Depending on age yours maybe/might be grandfathered in or will need to change. Will depend on each town/city regulations. Two towns beside each other might have different regulations.
    – crip659
    Commented Oct 5, 2022 at 20:02
  • does it serve as the main stack vent and the roof drain?
    – Fresh Codemonger
    Commented Oct 6, 2022 at 2:22
  • Odds are good that the roof slope was not corrected to help water flow around the sunroof which was, most likely, added after the roof drain. Not many sunroofs were installed in the 1880s to my knowledge.
    – FreeMan
    Commented Oct 6, 2022 at 13:11
  • @FreshCodemonger There are three separate vents. I think one is for all the bathrooms and kitchens. Two others are more recent additions for washing machines, I think.
    – user2503795
    Commented Oct 7, 2022 at 1:16
  • If you have separate vents then when it comes time to replace the roof membrane I'd get someone to frame up a 2% slope and do the standard gutter thing can just get rid of the roof drain in the middle. Have gutters and downspouts and get those to empty into the correct spot.
    – Fresh Codemonger
    Commented Oct 7, 2022 at 1:43

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The rules will vary with location,

I'm sure they want you to change, and when the whole plumbing stack is replaced they may require you to change. but absent that I can't see them requiring you to tear into three floors to fit a new storm drain.

Your roof surface appears to be butyl rubber done properly that stuff is watertight and frost resistant, a few puddles will not be a problem.

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