Need 2-1/4" x 8-3/4" ID PVC ring for a roof drain overflow?

[Doug Harris]

I have a flat roof with 2 Jones Stevens R18014 PVC roof drains mounted side by side.
I need to raise the water inlet of one of the drains 2" so it can act as an overflow drain if the first drain were to get clogged. I thought I could slice 2" off a pvc pipe and mount it where I have the red lines in the picture, but the dimension is oddball. Is there any pipe or fitting that has a roughly 8-3/4" ID that I could use?

 

[WorthFlorida]

Is this a single family home or a commercial building?
Probably you'll need to seal the PVC pipe with roof and flashing sealant but it may not pass inspection if you are in a construction phase. If you remove the dome on one of the drains you could add a 2" or larger pipe using a fernco coupler.

There are roof drains sold with a dam built in the cover. Very common. There are hundreds of styles. This is just WATTS brand but there are others. https://www.watts.com/products/drainage-solutions/roof-drains



Here is one built as a set.
https://www.plumbingsupplynow.com/3-no-hub-code-blue-dual-roof-drain-with-double-dome

 

[Sponsor]

 

[Doug Harris]

It's a single family home, and the drains are already installed so I just need the 2" dam. I didn't consider doing it inside the cover, I'm going to open it up and see if I can get something in there.

 

[wwhitney]

Looks like you have a 3" PVC roof drain? Jones Stephens doesn't seem to make a "dam" dome for their drains.

How about taking a 3" inside fit PVC closet flange, cutting off the flange, and gluing the inside fit pipe segment into your 3" PVC? If that doesn't get you high enough, but does get you 1" exposed extension inside the roof drain, you could glue a short section of 3" PVC over the inside coupler to get the height you need.

https://www.supplyhouse.com/Sioux-C...e-w-Stainless-Steel-Swivel-Ring-4-Long-Outlet

Cheers, Wayne