While I am still shopping the new gas water heater, I managed to bring down the old water heater and move it out to the street for bulk waste collection.



When I walked back into the garage I heard a loud clunk and it was the gas vent falling down. I should have learned the lesson because the same thing happened to me a few years back cutting a vertical section of 3" cast iron pipe out to lower the sanitary tee connection, I removed the cut section, walked away to find something to strap or restrain the upper section, only for it to fall out of the roof 5 seconds after I got up and crashed into the lower section below, creating a crack that went deep into the elbow under the slab so I had to cut open the slab.

This time it was that vent pipe coming down.





How is this connected to the fixture on the roof? Is it just a friction fit or do I need to go up the roof to remove the cap to reconnect?

This is what the ceiling hole look like where the vent used to pass through.

Sum, the proper way is to extend the pipe at least 2' above the roof and use a strom collar and b-vent cap. Also make sure the hole through the roof deck plywood has proper clearance. Seal the storm collar to the pipe with silicone.

steve, to install the strom collar and b-vent cap I need to remove the waterproofing and tiles right?

Right now I have this kind of vent, but I am a bit wary of messing with it on top because of it's proximity to the electrical weatherhead.

I would unscrew the top, trim the top of the jack flashing if a larger diameter hole is needed for the pipe to pass through, reinstall the screws to seal the holes and then install pipe, storm collar and new b-vent cap. Add a piece of b-vent to the bottom of the stack, due to the pipe now extending up above the roof surface.