Our flat rubber roof has twelve 3" pvc pipes protruding that are 4ft tall. They are bunched together in a 3ft square, and there is no room for rubber top hats. They are currently sealed with caulking and I'd like to secure them better. Will a pitch pocket provide a better seal and prevent them from moving? Peter Bassney

Are the pipes in a line or scattered? A pitch pocket or any other roof component should not be used to prevent movement. The pipes should be secured solidly to the structure. A picture would sure help.

Other questions are: will the temperature of the pitch affect the pipes? Is the plastic pipe chemically compatible with pitch? Three feet by three feet is a mighty big pitch pocket. Can you offset the pipes below the roof so that each pipe can have its own boot?

Pitch pockets are not designed to support any pipes of any kind. You need to properly secure them below the roof line or install guide wires above. While pitch pockets will support for a short while, they will end up leaking and your support will also diminish with age.

As far as sealing them, no issue with doing them correctly. But they do make rubber hats that can be secured to the pipes and then flashed into the roof. But if your issue is that they are to close together to properly seal, then you will need to construct a curb around all of these pipes, then fill with soft asphalt. Pitch pockets are not filled with hot tar.

In the early days they got the name "pitch pockets" because they were filled with pure coal tar pitch. Today it is rare to even find a coal tar pitched roof. Because this is a rubber roof, do not use any asphalt or coal tar based pitch pocket filler!!! It will eventually deteriorate the rubber that it contacts. Use a filler that is compatible with your EPDM roof. Most pitch pocket fillers are urethane based today. 3'x3' is pretty big for a pitch pocket, but if the pipes are too close together to use boots, then you have few options. Just be sure the roofer installs and fills it properly. Have you considered adding 90 degree ells to the pipes and installing a dog house over them with a solid cap. The pipes would then exit on the side of the box making it easier to get a good seal?

This message has been edited. Last edited by: Maintenance 6,

Good catch Maintenance 6 on the EPDM roof I missed that. And your idea of a dog house with the pipes are also good. However as long as the PVC pipes are not process pipes or vents he should be able to do this. We do this will all HVAC refrig pipes.

Thanks for the replies. The 12 pvc pipes are in 3 lines of 4 pipes each. They provide inlet and outlet air venting for 6 gas fired HVAC units. I like the doghouse idea, but how do you secure it to a flat roof? Where can i post a picture?

The "doghouse" should be anchored to a curb, which can be prefabricated or built on-site. The curb facilitates correct flashing of the joint between "doghouse" and roof. It can be built out of something like 3-2x6 (pressure treated), then frame th doghouse on top of that. You anchor the curb to the roof structure inside the curb.

Did you consider offsetting the pipes below the roof so that there is enough space for the boots on the roof? That would make the doghouse unnecessary.

If you opt for a prefabbed curb to place the dog house on top, it should be an equipment rated curb and should be a minimum of 8" in height above the top surface of the roof. It will have a flange around the perimeter to anchor to the roof deck and then get flashed into the roof. The beauty of the curb is that you will have about 16' of very standard perimeter seam in the rubber roof. With a pitch pocket you'll have the same amount of perimeter seam, plus about 10 feet of joint around the pipes. Boots around the pipes will be even higher. Any way you can minimize linear feet of joints or seams is a plus on a flat roof, especially a single ply membrane like EPDM.

I did consider offsetting the pipes below the roof, but I don't think the 6"-8" of available space is enough for this to be practical?

If a doghouse is built, can all of the vent ends remain under the roof and transfer air through a mesh screen? This would avoid the need to match all of the vents up with holes through the wall of the doghouse.