Help needed with plumbing vent relocation

Current scenerio: Vent pipe goes up to 7' inside exterior wall. 45 elbow directs vent pipe into garage. Another 45 elbow in garage sends pipe vertical through garage roof. Looks like this-> | | / / | | Problem: It's a 2 floor house with attached garage. When vent pipe exits garage roof, it's right next to 2nd floor exterior wall. 1) Exterior wall needs to be resided and contractor wants the pipe moved to ease his repair job. 2)Vent pipe collar flashing thingy extends under current siding. The house has original siding and then vinyl siding over it and that makes siding go over the vent collar.
My Proposed solution: Cut vent pipe in garage after first 45 elbow exiting from wall. Add second 45 elbow to make vent pipe go horizontal. Add another 12" pipe to move it further away from wall. Then 90 elbow going through new hole in roof. Like this-> | | / _ _ _/ / / | | Questions? 1) Is it legal to make vent pipe go horizontal? 2) How far does the vent pipe need to extend above the garage roof? I was going to measure the existing one, but the code could have changed since the house was built 45 years ago.
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Bob B wrote:

I don't see any problem with your solution. But...there is NOT a single unified Code in this land, so the ultimate decision is up to your local inspector. The size of the pipe used for a roof terminal may also be dictated.
The height above the roof may be regulated depending on things like anticipated snow load and frost closure, but 1 Ft is usually enough.
The horizontal section must slope upward toward the roof terminal, so that condensation drains back. (The fittings have this slope built-in, so that's not usually a problem.)
Jim
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Here that would be fine as long as the overall trend is up. 3" minimum sized pipe at least a foot above the roof. Your local codes may dictate otherwise.
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I'm thinking that the existing arrangement may not meet many codes as it is. It seems pretty close to the side of the second story if you can't even get a piece of siding between it and the wall. Any snow or debris (leaves, etc) build up could block the vent.
I've moved several over the years for various reasons (one would be going right thru the middle of my bed right now if I hadn't moved it when I added the 2nd floor to my house). Keep some slope to the pipe (downward from the roof) and stay with the same sized pipe. (size of vents will vary depending on local codes, and in some places only one vent needs to be as large as 3".
Your roofing is going to be the biggest hastle in this job. Make sure your siding guy flashes the area where the old vent was properly.

sized
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