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Tweedy
Dripping water down vent pipe

When we remodeled my bathroom, replaced part of the vent pipe with pcv. Ever since I have water drip down, so much I have to catch it with a bucket. Not in the summer though. Rebooted it on the roof, didn't help. Had a friend go in the attic to see if it was running down the pipe from the roof, could not detect any. We are stumped.

canuk
Re: Dripping water down vent pipe
Quote:

Not in the summer though

A couple of things come to mind .........

Is the penetration for the vent pipe into the attic well sealed?
This might be caused by condensation dripping down the vent stack
A good method would be use a can of spray foam to ensure a tight air seal around the vent pipe penetration into the attic. This will prevent warm moist air from rushing up the cavity into the cold attic and condensing.

The other thing would be if the connection for the PVC was made to a cast iron vent stack ...... the coupling connector might be leaking. This could also have condensation dripping back down form the warm air in the pipe condensing when it meets the colder attic.

Just a thought.:)

Tweedy
Re: Dripping water down vent pipe

I thought about sealing off the opening but was afraid the water would pool in the cavity and ruin the dry wall or worst mold

mcarolchap
Re: Dripping water down vent pipe

I am having a similar problem - the stack pipe itself is sweating where it goes through the roof . What a;bout insulating the pipe itself??

canuk
Re: Dripping water down vent pipe

Sure you can.
Trying to keep the air inside the pipe warmer will help to prevent condensation.

keith3267
Re: Dripping water down vent pipe
Tweedy wrote:

I thought about sealing off the opening but was afraid the water would pool in the cavity and ruin the dry wall or worst mold

There isn't any water in a vent pipe other than rain water. You need to keep the cold attic air from mixing with the warm moist inside air causing condensation in the wall cavity. Seal up the opening to the attic and your problems should clear up. Don't insulate the vent pipe, that will allow the outside air coming down the inside of the pipe to make it colder, not warmer.

canuk
Re: Dripping water down vent pipe
keith3267 wrote:

There isn't any water in a vent pipe other than rain water. Seal up the opening to the attic and your problems should clear up. .

For the most part that's true however , the sewer gas contains lots of moisture. When it's allowed to suddenly cool it will condense on the inside or it may cause the outside of the pipe to condense by warming the surface within a colder attic space.

Quote:

You need to keep the cold attic air from mixing with the warm moist inside air causing condensation in the wall cavity.

Yep --- totally agree.

Quote:

Don't insulate the vent pipe, that will allow the outside air coming down the inside of the pipe to make it colder, not warmer

Actually by insulating the outside of the pipe in the cold attic space is helpful. By keeping the pipe warm prevents the moist air inside the pipe condensing when the surface of the pipe becomes suddenly colder.

Re: Dripping water down vent pipe

roof leak - dripping down vent pipe.

When it rains there is a minor leak down the 4 inch metal (galvanized tin i guess) vent pipe that feeds down through the roof to the hot water tank. There is a much larger vent pipe for the furnace which is installed in the.

Anyway, what I can definitely tell you is that water runs down the outside of the 4 inch pipe and then drips when it reaches an elbow below. What gives???? dbteeitup.

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