running pex in a basement replumb job

I bought an old house which needs to have the water supplies replumbed (It has the old style butyl pipe, and I am refinishing the basement)
I intend to run 3/4" Pex from the entrance (about half way down the 40 ft length of the house) in about 15 feet to where most of the fixtures are located, then right angle turn and run about 16 feet drilling thru the 2x10 joists, then right angle and run about 6 feet to the hot water tank. Then run the 3/4 hot water pipe back parallel to the just run cold water.
Then I would tap off with 1/2 inch pex to the various fixtures between the joists.
Question: I would have to cross 2 five inch furnace hot air pipes when I drill thru the joists. Will that be a problem with pex being near or touching the furnace pipes ?
If so what is the best way to separate them
Thanks for any info
Ray
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Hot air produced by a forced air furnace is cooler than hot water so the "hot air pipes" (hot air ducts), as you call them, won't be a problem. If you can touch something comfortably than PEX will be fine.
The furnace flue is an entirely different story.
One of the benefits of PEX is the material is much cheaper than copper and much easier to run & make connections. I would suggest doing some research on PEX installation, consider doing a "home run" installation. Unless you're going to finish the basement ceiling, there is no need drill through the joists. If you do drill, keep the hole out of the middle 1/3 of the span & drill in the middle of the joist depth. Also stay away from the extreme ends of the joists.
A "main & branch" system is certainly ok but a home run system has lots of advantages.
check out http://www.huduser.org/portal/publications/pex_design_guide.pdf it should answer all of your questions
also
http://www.energy.ca.gov/title24/2008standards/prerulemaking/documents/2006-05-18_workshop/2006-05-11_PEX.PDF
cheers Bob
. Thanks for the information, it is very helpful... I considered a home run system, even bought some manifolds from Home Depot, but couldnt find a logical and accessable place to locate them.
I am going to finish the ceiling, so I would like to drill the joists, but 2 retired plumbers at Home Depot advised agains running the Pex near the heating ducts so I thought I would check the concensus here.
Thanks Ray
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On 2/2/2012 12:14 AM, Ray wrote:

just nail them up to the underside of the joists with the one nail hangars.
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Steve Barker
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