Basement Plumbing Question

I am finishing my basement and plan on adding a wet bar, shower, sink and toilet. I am going to have to dig into the basement floor to add the drains and I am have figured out how to do that. I know I need to vent all 4 of them. I cannot use a Air Admittance Valve because of codes.
I have found a 2 inch vent that come off of a bathroom on the 1st floor and heads up through the roof. My question is if I can put a tee on that vent with a 90 degree turn down and run it down to the basement and use it? Is there a limit on how many sinks, toilets, showers a 2 inch vent can handle?
Also, once that vent pipe is in the basement can I just run it through the joists to the places I need it? I assume I can just run the vent pipe along the ceiling and put tees when I need to run to the drain vents that I run up through the basement floor? Is there any sloping requirements for long runs of vents? The bathroom will be about 25 feet from where the vent comes down from upstairs.
Any feedback on if this would work would be great. Thanks for your help!
Sheila
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Sheila wrote:

In general, you have a good plan. Codes do vary, but a 2" vent should be more than enough for all the fixtures you will have.
The vent pipe must slope downward toward where it will connect to the new fixtures. This is so that any condensate can drain. Connect all the TEE's in the vent so that their normal flow path will continue that flow. Slope at 1/4" per foot. You can use reducing TEE's to drop the 2" vent down to 1 1 /2" for all the fixtures except the closet. You *can* run thru the joists while maintaining the slope but you can wind up severely weakening the joists as the holes get closer and closer to the edge. It's also a PITA to snake the pipe thru. Your inspector may prefer that you not weaken the joists at all.
You'll need a San TEE where the vent makes its connection to the fixture drain (downstream of its trap). For drains like the shower which will be below the floor, that TEE cannot be "lying on its side", but must be turned so that it is at least at a 45 deg angle. That's done so that waste can't readily enter the vent line. Venting the closet (toilet) connection can be tricky and I would ask the inspector what he would prefer in this case.
Jim
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On 6 Dec 2003 21:07:57 -0800, snipped-for-privacy@yahoo.com (Sheila) wrote:

The answer to this part can be maybe. If you connect into the 1st floor vent above the first floor waste lines, the answer is yes. But if you connect below the waste lines you have a wet vent and except for special circumstances this is a no no.

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