[Shop-talk] PVC Vent Run

[Jim Stone]

Sorry for the delay, guys.  I was out of town when I first asked my questions and it has been pretty hectic here since I got home.  The manual specifies a pitch of at least 1/4” per foot and I only need about 5 feet of horizontal run, so the drop won’t be all that much.  I can probably handle that with the ‘slop’ in the fittings, but will use a heat gun to bend them if necessary.  The manual is a little confusing re: the maximum length with elbows, but as I read it, I am allowed 25’ (50’ with natural gas, but I have propane) of 2” pipe with 4 elbows.  Additional elbows reduce the run by 8’ each, so I have to be really careful there.  Still, I only have one at the moment and will need a second to head over to the right spot on the roof, so I should be able to make everything work, especially if I use a top hat vent at the top.  We’re going to try to get the building’s final inspection next week, so I’m planning on finishing this up this week.  I’ll write back if there is anything significant to report after the inspection.

As always: Thanks,
Jim

> On Jul 18, 2017, at 7:03 PM, Brian Kemp <bk13 at earthlink.net> wrote:
> 
> You can easily make a 95 degree elbow with a pair of 90s as suggested.  Make one of them a street elbow and the pair of elbows will be much more compact.  I do this with sprinkler pipe on slopes.
> 
> I've bent lots of PVC with a cheap heat gun from Harbor Freight.  Lay it on a concrete slab and roll it slowly back and forth as you heat about a foot of it for 1-2 minutes and it should bend easy and cleanly.  
> 
> Check code, but having elbows at the top to make a "U" may violate code.  It did many years ago for a plumbing vent.  The proper top would be better,  if you can't find one easily, I'd consider using a "T" so there is no requirement for the air being vented to change directions and flow down.  A "T" will stop rain entry, but not hinder air exit.  
> 
> Brian
> 
> On 7/18/2017 7:36 AM, Jim Stone wrote:
>> I need to refine the vent for the water heater in my garage that provides heat for the radiant floor heating system and on demand hot water for the attached living space.  Right now, the 2 inch vent goes straight out the wall, but the building code requires that it be 2 feet from a vented or unvented soffit, which means that the pipe currently sticks out about 3 feet from the outside wall.          It is high up enough that safety isn’t an issue, but it looks really crappy and I’d like to do something better.  I think the best solution is to install a 90° elbow, run the pipe a couple of feet away, and then go straight through the soffit and vent vertically with a couple of elbows at the top to form a “U”.  (The design of the building doesn’t allow me to simply elbow and go straight up from the current location.)  Now, here’s the problem:
>> 
>> I can accomplish everything described above and still stay within the maximum length for the vent pipe plus the elbows.  However, the manufacturer also specifies that the run should be pitched back towards the unit ¼” per foot so that condensation runs back down and drains.  I have room to do that, but a 90° elbow off of a pitched horizontal pipe would put the vertical run at a similar angle.  (I hope that makes sense.)  It would seem like I need something like a 95° elbow.  Does such a thing exist?  I MIGHT have room to elbow out and up to eliminate the problem, but that would look like crap and the extra elbow would impact the allowable run.  I have tried heating and bending PVC before, but that doesn’t work very well.  Since pitching pipe for drainage is a common requirement, I have to assume this isn’t a unique problem.  How do I handle it? 
>> 
>> Thanks,
>> 
>> Jim
>> 
>> 
>> 
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