Question:

Hi Bob,

I have been having a problem with my plumbing vent. On occassion, when i flush the toilet i hear some gargling from the bathtub drain. It appears that the vent is clogged (frozen). I have gone up on the roof to unclog it (once a week, approx.) and then it works fine. Is there an alternate solution to this problem? If i choose not to unclog the vent, will it damage the pipes?

Thank you.

Answer:

Dear Sandro:

This is a common problem when the weather gets extremely cold. The moisture from the rising sewer gases hits the frigid air and freezes at the top of the stack and effectively closes it off. This problem can also happen if there are long horizontal runs of the vent pipe in the attic space as frost and ice build up and close off the vent. Vents allow the air pressure to equalize in the drain when the toilet is flushed so the water can move freely through the pipe. When the main vent is blocked off the air pressure will seek other means to normalize itself (eg. through the sink drain)

For the most part this problem is only a nuisance and will rectify when the weather warms up. I would not worry about trying to unclog the ice from the vent unless things like the performance of the toilet start to deteriorate (eg. slow flushes)or if you should smell sewer gas odour coming out of the drains of the sink and bathtub. The gas odour can be stopped effectively by running abit of water in the affected fixture to fill the p-trap again. If the toilet is affected you will want to consider ways to prevent the stack from icing up in the first place. There is no one answer to this but by keeping gases in the stack warmer as it passes through the attic should help to disapate the ice build up. An insulation wrap around the stack may provide enough heat retention in the rising gases to keep the vent open in the cold weather.

Let me know if this helps.
Bob

Answered By: Bob Steele

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