4" Storm Drain into Basement...

[chris.b]

This 4" Cast Iron (1o0~ yrs. old) is servicing a 3-story gutter, and drains into the horizontal soil pipe (10~ ft. before the stack). To replace this with PVC, what would normally be done (e.g., to comply with UPC/IPC)?

The trap appears mandated by Philadelphia code (gutter <12ft. from a window):
P-1001.5 Traps.
Leaders, yard drains, and other storm drains connected to a combined sewer shall be effectively trapped, except that inside leaders connected to roof outlets are permitted without traps if they are not located directly below a door or window or other ventilating opening of the same or an adjacent building nor within 12 feet of such an opening.

... which is fine, considering what could go down the gutter. However, are fittings like this even made in PVC? I've seen 4" PVC P-Traps available, but how do you go about a functional clean-out? I've only seen 2 in. and below P-Traps with (sediment) clean-outs available from manufacturers.



Thanks,

 

[Jadnashua]

Don't think you'll see a fitting like that in PVC since what is there now is a perfect example of an S-trap that is no longer allowed!

Most places are specifically trying to separate sewer inputs from storm drains, but your city may not be at that point (yet!). A big storm can overwhelm a typical sewage disposal plant, causing raw sewage to be discharged, which is the main reason it is being discontinued.

If still allowed, you'd have to actually use a P-trap, and bring the vertical line down further so you can then run the trap arm (outlet) of the p-trap into the main sewer.

 

[Sponsor]

 

[chris.b]

Don't think you'll see a fitting like that in PVC since what is there now is a perfect example of an S-trap that is no longer allowed!

Most places are specifically trying to separate sewer inputs from storm drains, but your city may not be at that point (yet!). A big storm can overwhelm a typical sewage disposal plant, causing raw sewage to be discharged, which is the main reason it is being discontinued.

If still allowed, you'd have to actually use a P-trap, and bring the vertical line down further so you can then run the trap arm (outlet) of the p-trap into the main sewer.

Thanks for the reply.

Philadelphia appears to have a "combined sewer", where storm water pipes and sewage pipes aren't separated. By Philadelphia code, it looks preferable to drain into sewage, unless you have a large property to disperse run-off into. I'm guessing it has been this way for 100+ years.

As for the S-Trap, yes, I was intending to replace it with a P-Trap, but it would have to be raised above the main soil pipe. There is another 10+ foot of soil pipe sloping (1/8") uphill from this pipe (around a bend), which not only serves another storm drain (coming horizontal through the foundation), but may in the future service a bathroom. In considering what debris and/or obstructions may come down the gutter, I would think a clean-out very necessary for the P-Trap, but am not sure how that's done in this situation.

I guess the reason I'm finding little resources on this problem is due to the fact that a lot of cities do separate these drains?

 

[Themp]

Why not just keep it? 100 years and still operational. Does it being an S trap really matter since it just goes to the outside gutter three stories up? If it does siphon it acts like a vent. I guess vents do have certain restrictions in terms of how close to windows and such. I would talk to a building inspector from your area.

 

[chris.b]

Why not just keep it? 100 years and still operational. Does it being an S trap really matter since it just goes to the outside gutter three stories up? If it does siphon it acts like a vent. I guess vents do have certain restrictions in terms of how close to windows and such. I would talk to a building inspector from your area.

Thanks for the reply.

It was the original plan to keep it, and is the reason it's supported by blocks. However, after replacing the stack & majority of horizontal soil pipe with PVC, we realized the storm-drain must have dropped/settled some time ago (previous owners, 20+ years ago, not sure). Now, the 1' PVC section preceding this fitting is at a negative slope, and the only way to correct that -- that I can think of -- is to replace the fitting with PVC, or... somehow raise the fitting itself (which may be corroded, brittle, and at least involve opening up a large section of the foundation).