Finishing Basement - Expanding Existing PEX Sytem

Hello. This is my first time posting here, but not my first time reading on the forum. Indeed, many of my decisions regarding plumbing while building our home were influenced by this site. It's two years later, and we're considering finishing the basement.

We're in a 2500 square foot ranch. The basement was "roughed" for a bathroom, which means it has drain/vent pipes. The rest is up to me .

The existing living area is services by what I think is a "trunk and branch" system. We're on well water. The branches start from a manifold, which feeds a series of 3/4" PEX pipe. That pipe then feeds the rest of the house, and, where appropriate, it's reduced to 1/2" to feed fixtures, etc.

For the basement project, we want to build a new bathroom with lavatory, shower (no tub), and toilet. We will also install a wet bar.

If I were to guess (and I know I shouldn't) typically the bathroom should have its water delivered via 3/4" pipe, then branch out from that to feed each fixture. Problem - the existing PEX manifold is full.

Can I use any of the existing 3/4" branches to supply the basement fixtures? For instance, I have 3/4" tubing directly above where the bar sink will be. Those feed a shower upstairs. That sink downstairs will get very little use. I can see putting a "T" in that PEX to feed the barsink.

Tapping into any of the existing lines for the bathroom fixtures is a different story - obviously much higher rates of use, and I wouldn't want to screw something up.

What are my options here?

1. Call pro. Forget about DIY at all.
2. Call pro. Have them install/branch/etc a new line for the basement.
3. Tap into existing stuff myself.
4. Forgot about the basement all together. Learn to live in peace upstairs.

Hey! Some photos of the existing setup....

http://www.flickr.com/photos/kpfeif/sets/72157622171012731/

water

A plumber would probably connect to the copper water lines somewhere near the new bathroom and not even bother with the existing PEX lines.

There are no copper lines near the new bathroom...near, is of course, subjective.

The two lines that supply the PEX manifolds are accessible down there...tapping into those copper lines there is a possibility, then.

Some manifolds are designed to allow an additional one to be attached in series. Is there any fitting on the end of yours? You may be able to just add a new one to get more taps. It would be fairly easy to put a T in the copper supply line and either run it with copper or pex from there. You don't need a manifold, just the conversion fitting if you want to use pex into the copper supply. Note, 3/4" pex has a smaller internal dimension than 3/4" copper (the outsides are the same dimension, though).

manifold

His manifolds do have caps on the ends, but by the time he got all the water out of them to remove the caps and then solder new fittings on he might create additional problems.