I seem to be having a bit of an issue with my floor drain in my basement.
I live in a upper/lower style duplex and my upstairs neighbor has been having some drainage issues as well.. The house is quite old and I don't know when the plumbing was installed, but since the spring thaw, my neighbor and I have been noticing slow drains and I've been having my basement drain get backed up.

I notice it most when I run my washer in the basement. It drains into a slop sink that's attached to the main (4") pipe. I did find another post and found that the slop sink is not ventilated as it should be... but, I don't believe this would cause all my issues.

I also recently noticed a vent pipe outside that I may have accidentally hit with my snowplow last winter, as it's very easy to move in the ground. (picture: http://i29.tinypic.com/2u750z7.jpg )

I'm not certain, but if this is the only ventilation to my drainage system, and if there's dirt getting into the broken pipe, could this cause the issues I've been having?

Are you on a septic tank or city sewer? Back to you, Tom

City sewer...

Is your rainwater runoff water tied back to your sewer line? Tom

I'm not 100% sure, but I believe it is...

In my area it's illegal to discharge anything but sewage and gray water into the city sewer. The reason is two fold.
1) The cost. They have to process rainwater the same as sewage.
2) The volume. A heavy rain can overload the system.
And I believe that's what's happening to you. The solution would be to route your run off to a dry well or water the garden with it.
That vent also doubles as a clean out. Repair the pipe so dirt doesn't get in your line. Good luck, Tom