Sewer vent pipe frosts over....need solutions!

[thorski]

Hi everyone-

When the weather gets really cold (below zero)my sewer vent pipes like to freeze up and it gets smelly in the house. Can anyone suggest a fix to this problem. I would like to do something now before it gets real cold. Thanks.

[Eelpout08]

If there is a screen on the end of the pipe i would take that off. how much pipe is above the roofline?

[reddog]

How big is the pipe?

[Dave S]

I have the same issue. I think the pipe is a 2" pvc and is about 12" above the roof.

It gets a little old going on the roof every couple weeks with hot water to melt the ice. I don't really care to put a heat tape in there either.

[Eelpout08]

The more pipe there is above the roofline and exposed to cold air will give the moisture in the air a chance to condense and freeze. i would cut the pipe closer to the storm collar/flashing so there is less pipe in the elements.

[Steve Foss]

Larger diameter pipe means more opening to remain when frost/condensation builds up. I also like it kept close to the line of the shingles, but on flatter roof pitches you'll have to keep it clear of snow through the winter. Aside from the bad smell of a plugged sewer vent, you've got some serious methane gas poisoning potential, so I'd definitely work toward a solution.

[jeffreyd]

dont you need to have it a certain level above the roof to allow for the pipe to vent properly? i would be afraid that cutting it down low, you might create a venturi affect and actually push the gas back in the house. If you can find your plumbing code online it would tell you the min height allowed. how about just wrapping the pipe with some of the insulation foam?

[Tom7227]

I remember reading something about this a year ago. vague memory was that one answer was to hang a piece of copper pipe down the center of the PVC. The copper conducts heat and keeps things open. I think the writer put a full 10 feet down. It wasn't hooked up to anything, just hanging in the PVC.

[Surface Tension]

2" vent will give you trouble with freezing. 3" or even better 4" for MN. That dia should be at least 1' minimum below the roof line.

We think of the vent expelling gases outside and it does somewhat when your not draining anything. The vent actually sucks in air whenever water is run out a waste line. Plug the vent and the draining water will suck water out of one of the traps in your home and the reason for the smell. Until you can solve the freezing, figure out which trap is draining and let about a cup of water run to fill the trap. Anymore water then that and it'll siphon the trap dry again.

So you have the 2" vent freezing up, besides increasing its size to 3" what else can you do? Insulating the vent pipe above and below the roof line might help. 6' of 1/2" copper pipe hung inside the vent in theory transfers its heat and keeps the vent open.

[walleyeseeker]

The best solution is to change the roof cap to a frost free type. It is a galvanized pipe cover with a lead ring on the end to seal around the pvc pipe. This helps to trap the escaping heat and use it to keep the pipe open.

[Redlantern]

Walleyeseeker is right on. The galvanized roof jack for the vent will probably be your best solution. Pain in the butt to do now that the weather has cooled a bit and the shingles are a little stiffer. A temp solution would be heat tape but then you need to have a cord hanging off your roof.

Minnesota plumbing code states that a vent pipe through the roof shall not be less than twelve inches above the roof.

If you were to have it less than that, snow will probably end up covering up your vent pipe anyway and you have improved nothing.

[kkahmann]

I had this same problem last year and like Tom I read how to fix it on here. I live out in the boonies and don't have a code or anything to worry about. Mine is 3 inch PVC and it sticks out of the roof right up near the peak. Only sticks out about 6 inches. I drove a nail thru a 4-foot piece of 2-inch black ABS--about 6-inches from the end--dropped that down the 3 inch pvc. End of problem.

[Phred52]

thorski, Back in the days that I worked in the mobile home park, we had a few houses that were 'problems' in that respect. We did find a couple houses that there just wasn't enough of a 'p-trap' on the pipes so we just added 3" of PVC so the winds couldn't suck the water out of them and allow gas to escape. On the others (without the above problem) we'd wrap the exposed vent pipe with regular 'pipe wrap' (4" fiberglass insulation) like what's used on the fresh water infeed line and that seemed to cure the problem. Another thing that could be tried is to get a short length of 'heat tape', 4 or 5' should be enough, (the stuff that you plug in and it heats up) Drop that down into your vent pipe and when the temperature drops to that where you'd get frost, plug it in. That'll keep that pipe open for sure!! Phred52

[thorski]

Thanks to everyone who offered advice. It is amazing the help a person can get from this HSOforum! If a person has a problem, just post it, and someone will have a solution.

I am interested in the "frost-free roof cap" solution. Can I get the caps at any home improvement store? Otherwise I might try the black ABS pipe solution. I assume the nail through the black ABS pipe rests on top of the larger vent pipe to keep the ABS from falling down in, correct?

I plan on trying to tackle the problem this weekend. I'll let you know what I did and whether it worked.

Thanks all!

[Tom7227]

The frost free vent pipe should be available at any decent home improvement store. The problem you have with it this time of year is that the shingles won't want to come up and you run the risk of breaking things and not getting stuff sealed back up properly.

I bit my tongue when I read the black pipe idea. The reason for the copper pipe is that it will conduct heat upwards very efficiently. The black pvc won't do that. In fact it won't do it any better than white pvc or any other color you can get. If we were talking about using heat from the sun I would still disagree that the black pipe because it doesn't conduct heat. The idea is to move the heat from further down in the pipe up to the top and prevent ice from blocking it all off. You are relying on conducted heat. The pipe cap jobberdo will provide insulation around your existing pipe and that is how that will work. You can lay the copper pipe the same way that the recommendation was for the pvc.

[Ballyhoo]

Have used the copper pipe method. I actually heard about it on the news about 10 yrs ago. The Devils Lake fire dept was getting called out for gas smells and when they got to the houses they put the copper pipe Tee down the vent. The trick with it is to make sure the end of the copper sticks down below the ceiling so it gets into the warm part of the house. It is the heat conduction up the copper that keeps it thawed.

[Redlantern]

I really don't like the idea of putting something down your vent pipe. Last year someone asked about knocking the frost out, I suggested using something like a broom so it couldn't fall down the vent. Guess what? The broom handle became loose and fell down the vent. Not sure if the vent stack was a straight drop to the basement or not. Best case scenario if you drop something down your vent is you need to breake the attic access seal, climb through your insulation, compacting it, find the vent, hope it's plastic, cut it apart, get the lost item out, glue the pipe back together, get out of the attic without bringing all the insulation out with you. Worst case, cast iron bell and spigot pipe, Extra Heavy, of course, straight shot down to your finished basement and it plugs things up. Now your looking at tearing the old pipe out, along with the backed up sewage that will suddenly be freed to go wherever it wants to. Typically all over the person repairing the problem. Sound cynical? You bet I am. Don't stick things down your vent pipe.

[bak2MN]

The home improvement stores or a fleet store sells a insulated type cover you just put over the pipe that is sticking out of the roof. It looks like a football, is black with foam on the inside and they sell them for different sized pipes. I put them on and have not had a problem. Sell for around $25. Sure would be easier than replaceing a roof jack as you will probably damage your shingles this time of year. And I wouldn't stick anything down my pipes either.