I know this topic has already been discussed, but I was hoping someone has some advice that will work for me.

BACKGROUND:
I live in Northern (nearly Arctic) Canada. The weather here gets extremely cold here for a really long time during the winter (we're talking -30's to -40's for months). My drain vents are frozen. I do not have an attic where I can unplug the problem from inside and it is not possible to get onto the roof during the winter. I hope to fix this problem in the summer but I need some suggestions.

We have been living with the problem of sucking bath and sink drains every time we flush a toilet or do laundry. As long as I top up the drains and keep the traps full of water I can avoid the terrible smell that comes from the sewer.

I'm nearly positive that I have 3" PVC vent pipes which extend straight up from each drain and poke through the roof (x3). From the road, I can see a small bit of ice on top of each of these pipes so I'm quite sure where the problem is. I live in a Townhouse Complex and the funny thing is that I can see the same amount of ice or worse on top of everyone else's vents but, as far as I know, I'm the only one who is suffering from this problem of sucking drains and bad smells.

QUESTIONS:
1. Am I going to damage any of my plumbing by continuing to live with the problem the way I am?

2. Is my family at risk from these gasses or are they just an annoyance?

3. I don't think that heat tape is an option because there is no attic and if I put it on the pipe above the roof, where would I plug it in?

4. Would insulating the pipe exposed above the roof do anything to stop icing over?

5. Is there some kind of cover for the top of each vent that solves this problem?

6. Why is this happening to me and not my neighbours?

I will be getting on top of the roof in the summer and I intend to cut each vent pipe at a 45 degree angle to make the hole larger as suggested by someone else, but I don't know if this will really solve the problem.

I would be grateful to anyone who has experience with this problem and has suggestions that will work.

Thanks!

QUESTIONS:
1. Am I going to damage any of my plumbing by continuing to live with the problem the way I am?

2. Is my family at risk from these gasses or are they just an annoyance?

3. I don't think that heat tape is an option because there is no attic and if I put it on the pipe above the roof, where would I plug it in?

4. Would insulating the pipe exposed above the roof do anything to stop icing over?

5. Is there some kind of cover for the top of each vent that solves this problem?

6. Why is this happening to me and not my neighbours?

I will be getting on top of the roof in the summer and I intend to cut each vent pipe at a 45 degree angle to make the hole larger as suggested by someone else, but I don't know if this will really solve the problem.

I would be grateful to anyone who has experience with this problem and has suggestions that will work.

Thanks!
[raised in florida]
1- no
2- the gas is methane gas and there is some bacteria in it. You are doing well in refilling traps
3- you can run an extension cord to a receptacle
4- no. I would think it is icing over because it has a lot of moisture rising up. You may consider increasing to 4".
5- increasing the size of the opening would help, a cover may not help because it may decrease the size of the opening.
6- it is happening to you and not your neighbors because you are just lucky that way [joke]
How do you know it is not happening to your neighbors? What are they doing differently? Florida is nice this time of year, maybe you could just hop down to Florida for the winter [smilez]
The 45 degree thing sounds like a good idea. Maybe it is what the neighbors are doing.
[ I hope you enjoy this post, I had a nap and feeling a bit frisky]

The reasons for the freeze up of the vent has many reasons and for most of these you can do very little. The 45° cut on the stack at the roof may help a little but I doubt it.

Different plumbing setups with different conditions can cause yours to freeze whereas your neighbors does not.

Pouring hot water down the stack from the top may thaw the clog but it's risky being on the roof in winter and it won't prevent it from reoccurring.

Heating the pipe is an option even though you don't have attic access because you can heat it from the inside with a narrow heating cord. I saw this described on a site at Frozen Vent Stack and Water Lines

Something you might try, it probably won't work but you have nothing to loose. If you are on a septic tank, fill all drain traps except one. Take a shop vac and hook hose to exaust port. Put hose into drain that has no water in trap and blow warm air into system. If you are on municipal sewer system this for sure won't work but on septic system you might get enough warm air up to melt ice. Take a long time but if you ever get it open, doing this periodically might keep vent clear.

The simplest solution is to insulate the pipe where it passes through the unheated attic space. If this fails to solve the problem then heating cord or tape between the pipe and the insulation wrap will in most cases be the solution.

The only problem that's hard to solve will be if its occurring right where it exits the roof. But I'm sure that a insulation layer plus heating cord will transfer enough heat to reach that area as well.