If you notice discolored drywall on the ceiling, do not just ignore it. It is usually caused by the water penetrating from above. If the shingles are still in a relatively good condition, water is most likely seeping around the plumbing vent that goes through your roof. If this is the case, you’ll need a vent boot and metal flashing in order to prevent water leaks around your pipes. Vent boots are made from thin rubber which dries out and cracks due to sun exposure, allowing water to go down the pipe. If you replace the vent boot and flashing as soon as you notice the damage, this can save you literally hundreds of dollars. Here’s what you have to do.
Start by inserting the tip of the pry bar underneath the shingle that is directly above the shingle which sits against the pipe. Gently pry upward so as to locate the nails and then use the tip of the bar to remove them. Put the nails in a safe place and demount the shingle. There should be a semicircle cut into the bottom half of the shingle fitting around the top of the pipe. In case the shingles go over the sides of the flashing, loosen them up so that the sides of the metal flashing can be accessed.
The vent boot is an angled piece of rubber with an upward sleeve fitting around the pipe,located at the bottom of the pipe. You should twist the vent boot until it becomes loose, then pull it up and remove it from the pipe.
Now insert the tip of the pry bar tip beneath the metal flashing – first on one side, then on all others – to lift it up. If there are nails on it, remove them an put them in a safe place, as you will need them later on. Once the flashing is loose, simply lift it up and remove it from the pipe. In case the shingles on the sides don’t allow you to lift the flashing, slightly bend them back with your hands so as to access the nails and flashing and remove them.
Insert the new flashing over the top of the pipe (there is a hole provided for this purpose), and push it down the pipe until it is leveled with the roof. In necessary, raise the shingles on their sides in order to place the edges of the flashing underneath the shingles.
Put the vent boot over the pipe so that the hole in the boot is aligned over the pipe. Now pull the vent boot down the pipe till it sits atop the flashing.Apply a good quantity of flashing sealant underneath and along the edge of the flashing. In case the shingles go over the flashing on one side, you can access the flashing by lifting them up.
Once you’ve finished sealing the edges of the flashing, place the shingles back down.Now all it’s left for you to do is to replace the removed shingle above the pipe, using a hammer and the original nails to secure it. Congratulate yourself on doing a good job.