outside air intake

[hustont]

I have a Rheem high efficiency furnace in a 7 year old home. It was originally installed in an unfinished basement and uses indoor air for combustion (there is a pvc pipe with a t-fitting open on both ends coming out the side of the unit, which pulls in combustion air). There is pvc piped to the outside to exhaust. I am planning on finishing the basement and want to replace the current intake with pvc to the outside. The manual for the furnace says either set-up is OK. So my question is, any particular things I need to know about this project. Such as, are there a maximum number of elbows one should use in running the pipe? Is there a maximum length from the furnace to the outside? Can I use the standard two-part epoxy for pvc, or is there something special that is not flammable? The exhaust set-up has a 2" pvc coming out of the furnace, an adapter to increase to 4" pvc and than transitioning back to 2" to go through the wall to outside. Do I need the same set-up for the intake or is just running the 2" pvc from furnace to outside sufficient?

[HayZee518]

for combustion air you need as large a volumn as practical. each elbow is a restriction. why not use the flexible aluminum dryer duct with duct tape for joints? this way you can transition around a corner without creating a definate 90.