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neal singer 02-09-2008 02:07 PM

roof leak at puncture for airconditioner
Three years ago we had a roof air conditioner installed. It was fine for two years. But for the last few rain storms, water has entered our house along the pipe passing down thru the roof to the unit in our garage. The roof is flat, tar and gravel, at least 13 years old. No bubbles, and I've kept the sidewalls repaired where it merges into the parapet (typical New Mexican construction). The air conditioning folk have come out twice and re-tarred the pipe entrance point. Still leaks. They feel the leak is elsewhere and the water is funneling to the pipe and then down. Nothing obvious is wrong on roof. Any suggestions how to locate the source of this problem? thanks, Neal

Ed the Roofer 02-09-2008 03:11 PM

Does either duct work or a foam insulated piped tubing run through the parapet wall, or is the only penetration through the flat roof material?

Does it only leak when it rains, or is there evidence of interior staining during periods of high humidity conditions, where the A/C unit is creating significant condensation?

Is the ducting and the tubed piping uniformly insulated and sealed at any joints or junctures?

Is this a large A/C unit with an internal condensate catch pan inside the unit?

Does the pipe penetrating the roof surface have a properly installed and self leveling product installed in the pitch pan to prevent water accumulation from migrating through any cracks in the pitch pan filler material? Wiggle the pipe and see if there are any slight gaps or fissures which would allow moisture to enter, even if they look minor.


the roofing god 02-09-2008 06:44 PM

basically ,could this be built up condensation,rather than rainwater ??

neal singer 02-09-2008 08:13 PM

roof leak at puncture for airconditioner
thanks for the replies. Ed, a foam-insulated pipe runs thru the flat roof material, not the parapet;the roof only leaks when it rains. The piping is insulated and tarred on its vertical descent into the roof (about a foot in vertical length). The A/C is a 5-ton unit; I don't know whether it has an internal condensate catch pan inside the unit, nor what it would look like. Not sure it's relevant, since it's been freezing here and the A/C is off. (It's a combo gas furnace and A/C; the gas furnace and part of the AC unit is in the garage. The intake unit -- fan and maybe a condenser, not that sure how it works -- is on the roof; the leak occurs where the piping enters the roof but the A/C is not on.)
Re wiggling the pipe, I'll do that tomorrow in the daylight; thanks for the idea. I'm not sure what a pitch pan is; there's a plate that the piping goes through and I assume that's it, but it's under tar and I don't know much about it.
"Roofing God," this only happens when it rains, so I don't think it's condensation. Thanks for the reply.


the roofing god 02-09-2008 08:22 PM

sounds like you need a pitch pocket-usually that`s a metal box set around the pipe,and flashed to the roof at the exterior of the box,the n after the a\c tubing goes thru ,the box is filled with an elastomer or similar substance to prevent leakage caused byn typical expansion/contraction of these type pipes

neal singer 02-09-2008 08:29 PM

the first problem, though, is locating the leak. I've poured water from a 2.5 gallon bucket right where the pipes go thru the roof; I thought that would demonstrate the leak was at the pipes. But no wetness occurred. Might not have been enough water. Still.. not sure if that means leak is elswhere.

Ed the Roofer 02-09-2008 09:01 PM

This is one typical example of what a pitch pocket is. Now, since you mentioned that the foam insulation was intact on the pipe that penetrates through the roof surface verically, I would also ask that you check the brittleness of the foam wrap around insulation to see several things.

Is the foam brittle and deteriorating?

Is there any gaps or seams where in intersects the roof?

Even if someone slopped plastic roof cement around the circumferance of the insulation around the pipe, the roofing cement by itself will expand and contract until it becomes too brittle itself and loses its pliability. When that occurrs, the penetrating hole can only become more brittle and prone to additional cracking, even if very minor at first.

A slow and saturating rain will more likely find this roofing defect rather than an instantaneous deluge of a significant volume of water. The large volume of water from a 2 1/2 gallon bucket will too quickly disperse from the area in question. A better test would be a running garden hose pointed at this area if it is not trecherous and freezing on the roof surface or even better, a very close detailed eyeball view of the area penetrated.

If the tube actually goes through some sort of a pitch pan, aka, a pitch pocket, then check the sealant that fills up the interior of the metal flashing. You would be looking for cracks and a level lower than the perimeter edges of the sheet metal pitch pocket flashing.

Also, if the insulation is in direct contact with the pitch pocket filler, (usually just plain old roofing cement), then take a stanley box cutter knife and cut away several inches of the insulation where it is penetrating the filler compound.

At this point, but some very good polyurethane caulk, such as Vulkem Sealant and fill in the gaps and build up the pitch pocket filler with this sealant to form the appearance of an ice cream scoop on top of a cone. This will allow for the water to slide off of the material to the exterior of the pitch pocket and not settle in the center until it finds the minor cracks, which is akin to having a drain opened up in a sink.

Also, make sure thet you coat the noewly exposed portion of the pipe tubing that runs through which you have recently exposed by cutting away the insulation. This will cover up the future affects of not having that portion of the piping being uninsulated adequately enough.

Ed Pockets
Pitch Pocket

Pitch Pockets are flanged, open-bottomed, metal containers, placed around columns or other roof penetrations. They are filled with hot bitumen or flashing cement in order to seal the joint, thus blocking penetrations of the roof. Pitch pockets are easy to install. You can simply open it up and wrap it around the roof penetration. All that is required is some light hammering to the corner lock in order to hold it together. This quick installation provides a water tight seal. B&B Pitch Pockets are available with or without soldered corners.

neal singer 02-11-2008 09:33 PM

There's no pitch pocket on the roof. Instead, there's a flat plate about 15" square, flat onto the flat tar roof, through which the two pipes go down into my house. The pipes are covered pretty good with roofing tar. The pipes do not move when I try to shake them.
I tried finding a pitch pocket in my local Lowes and Home Builder's Supply without success. It doesn't rain much in New Mexico. I'll see if local contractor supply stores will sell to a private party. If not, I'm thinking of getting a nine-inch diameter stove pipe, cutting off a foot of it, locking it around the pipes, and filling it with roofing tar. I'd also set it at the base in a bed of roofing tar. Then its top would be above any standing water, and if I ice-cream cone the top with some kind of silicone as you suggested, Ed, -- what do you think? a little jury-rigged but it could work--?
thanks again,

the roofing god 02-11-2008 09:34 PM

try a sheet metal shop,or a local roof co.,to make one up for you,probably better

Ed the Roofer 02-11-2008 09:52 PM


Originally Posted by neal singer (Post 97120)

I'm thinking of getting a nine-inch diameter stove pipe, cutting off a foot of it, locking it around the pipes, and filling it with roofing tar.

I'd also set it at the base in a bed of roofing tar.

Then its top would be above any standing water, and if I ice-cream cone the top with some kind of silicone as you suggested, Ed, -- what do you think? a little jury-rigged but it could work--?
thanks again,

No, that would not work. The roofing cement would ooze down through the 9" diameter hole you had, unless you meant to not cut a hole that size through the roof.

The pitch pocket can be self made with an "L" shaped piece of sheet metal. Take tin snips ever even 4" to 6" and just cut the bottom flange. Do this continuously until you have 4 sides done equally and leave a little left over to overlap the last corner.

Then you would have to follow the instructions, (search = Dope and Minnie by Ed The Roofer) in this forum from many months ago to see how to properly patch in the exterior flat sections of sheet metal to the roof surface.

Here are the search results I suggested you look at for the repair using dope and minnie:

I would fill up the center of the pitch pocket with that expanding foam, one brand is called Great Stuff, and then wait one day for it to cure then shape it to the ice cream cone I mentioned before. You can use a rough textured anything and some finer texture if you want it to be real smooth.

Then after it is shaped properly, completely coat the hardened foam with about a 1/4" thick coating of a good polyurethane sealant, such as Vulkem Caulk.


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