Pipe Boot PVC Pipes

How To Repair A Leaky Roof Pipe Boot

 Hi, I’m David and I live just outside Raleigh, NC.  My contact information is under the tab “About Us”.

The most common roof leak occurs around plastic plumbing pipes and fortunately it is one of the easiest repairs to detect and correct.


Figure 1
If attic access is simple enough you may feel around these plastic pipes for wetness (during a rain) or look at where the pipe exits the roof for daylight penetration. Cracks in the rubber seal around the pipe will allow water infiltration. A simple on top of the roof inspection will reveal whether or not the pipes are in need of repair. (fig. 2).

attic access to check for moisture

Do It Yourself Roof Repair PVC Pipes: Figure 2

Around these pipes there is a hard piece of plastic which sits on the roof and a rubber ring integrated into the top of it which surrounds the pipe making a watertight fit. This entire component is often called a roof jack. (fig. 3)

roof jack for watertight fit

Do It Yourself Roof Repair PVC Pipes: Figure 3


The rubber portion of this roof jack will often begin to show visual signs of deterioration seven years or so after the roof has been installed. This will allow water to penetrate this seal causing a leak into the attic. (figs. 4 and 5)

roof jack deterioration

Do It Yourself Roof Repair PVC Pipes: Figure 4

broken roof jack

Do It Yourself Roof Reair PVC Pipes: Figure 5


It is common for roofers to replace the roof jack however; a new rubber gasket is almost always all that is needed on top of the old pipe jack. Unless the hard plastic portion has been cracked or damaged in some way it does not need to be replaced. On rare occasions when they do need replacement, the shingles will need to be separated from around the pipe area. Sometimes the shingles are sealed so tightly that it is almost impossible to separate them without damaging them. A new pipe gasket is a perfect and inexpensive fix. It is much better than using asphalt roof cement which will crack when the sun dries it out causing another water leak to occur (fig. 6)

new rubber pipe gasket

Do It Yourself Roof Repair PVC Pipes: Figure 6


A homeowner who can safely access his roof could easily perform this repair himself. You may purchase these pvc pipe boot gaskets from me for $8.00 each. Most houses have anywhere from two to five of these plumbing pipes coming through the roof which allows air to circulate through the drain pipes whenever the water is being used in the house.

Additionally, I use a commercial grade polyurethane caulking to adhere the rubber pipe gasket to the top of the roof jack for extra protection from water infiltration (fig. 7). One tube of this is plenty enough for one home at a cost of $6.00. I apply a bead of this sealant, no larger than your pinky finger, at the intersection where the hard plastic meets the old rubber ring portion of the roof jack. I also put a little dab of it on the exposed nail heads which fasten the roof jack to the roof. Make sure the hard plastic is tight to the roof where it is nailed.  If any of the nails are loose across the bottom edge of the plastic, a leak may occur there. Any loose nails should be removed and the nailholes filled with sealant. (fig. 7)

Polyurethane Caulking

Do It Yourself Roof Repair PVC Pipes: Figure 7


There are two different pipe gaskets that I use. The smaller one and the larger one.  I use the smaller one for the 1-1/2” and 2″ pipes.   The larger one is for the 3″ and 4″ pipes. Both pipe gaskets come with tearoff sections that can be removed for the larger pipe so it will fit snugly. Fig. 8 shows the smaller one.

Pipe Gasket Rings Vary

Do It Yourself Roof Repair PVC Pipes: Figure 8


Fig. 9 shows the larger one I use for the 3″ and 4″ pipes.

Bead of Caulking on Boot - After

Do It Yourself Roof Repair PVC Pipes: Figure 9


Note that each pipe measures about a half inch bigger than its designation when you measure its diameter. When measuring across the 1-1/2” pipe, the ruler will read almost 2 inches (fig. 10).

Measure 1-1/2 Pipe Properly

Do It Yourself Roof Repair PVC Pipes: Figure 10


Likewise a 2” pipe will read almost 2-1/2” (fig. 11).

2 inch pipe

Do It Yourself Roof Repair PVC Pipes: Figure 11


For the 3″ it will read about 3 1/2″ (fig. 12).

Measure 2-1/2 Pipe Properly

Do It Yourself Roof Repair PVC Pipes: Figure 12


Here is a 4″ galvanized metal pipe which is from an older home that has the new gasket already installed. I put sealant on the pipe also since it has a pitted surface.


Here is a tennis ball showing it’s comparison to a 3″ pipe – but don’t drop it in!



The ball can sit on top of a 1 1/2″ and a 2″ pipe