Sorry I can't answer your question- I think you would have to open the wall to find out where the pipes run. Mine take up a bit more that a foot of space, and you would have to frame around them as well to install the glass block, so that would be another 3-4" lost, then you have the corner framing on the walls that takes up space. It sounds like a lot of work- have you considered a Solatube? I put one in my shower and it works really well. It was easy to install- my husband and I did it in a few hours. Another option is to put a waterproof overhead light in the alcove.
Renee

Lachase: I really like that idea of runnng glass blocks along both sides of center strip containing the plumbing. I've been looking into that same thought, as I feel that it could make the bath area seem more open. I've seen magazine pics showing glass panels - but I'm now going to be looking into the glass blocks as a more cost effective plan. Have you pursued this thought any further?

Most common way is as has been described...an expanse of vertical glass block on either side of a central tiled vertical plumbing chase.

Alternative would be an entire wall of glass block with the plumbing being surface mounted to the face of the glass block wall. So all the plumbing is "inside" the shower instead of buried inside a wall.

The latter is done with mortar joints (usually) instead of silicone.

Mongoct: I love the idea of the entire wall done with glass blocks - and the plumbing is 'inside' the shower ~ I wish that would work with having just a hand-held shower and slide bar - no fixed shower head, but I suspect tht would end up looking too cluttered.....
This setup should work, though, if there were the central tiled vertical plumbing chase - with vertical glass blocks on either side, yes?

Here's an entertaining article on glass block: http://www.lifeofanarchitect.com/la-mort-aux-blocs-de-verre-death-to-glass-blocks/

It was a most entertaining article ~~ :)
But, unlike shag rugs and panel walls, I can see where glass blocks just might work - for me......

Lachase - What are your thoughts now?

Before I read the article I thought I liked glass block for some uses, but it did make me think twice about making a whole feature out of it when other products can be used instead. I think a frosted pane of plate glass probably looks more refined, uniform and simple for your application. Just be sure to put the frosting (or sandblasting, etc) facing outside of the shower .

Having the plumbing outside the wall, and exposed inside the shower, it could look cluttered I suppose. You can do a search for "freestanding showers" and you'll see some setups that could be modified for what you are proposing.

Don't overlook the idea that the plumbing supply lines can come through the floor or through the ceiling.

But your question? Yes, a central plumbing chase with glass block on either side would work fine.

There are also the commercially available "shower panels", but those are another can of worms. Depends on the look you want.