I am very grateful to the professionals who run this website!

I am almost ready to convert my house from copper to cpvc plumbing. Copper just doesn't last in my neighborhood and even plumbing professionals are recommending cpvc in my particular neighborhood. Someday, I will give all the details in a new thread.

I think I am down to my last technical challenge (wishful thinking), before the big job. I've researched and can't find anybody addressing this issue specifically....Should I attempt to fit 1/2-inch cpvc between a concrete wall and the furred-out drywall?

There is 1/2-inch copper pipe there now and it barely fits. The cpvc elbows are even larger. According to some website a 1/2-inch cpvc elbow has an OD of 27/32 = 0.844. The furred space is only 3/4 inch.

As you can tell from this crude schematic [i93.photobucket.com], the supply pipe enters the house in a wall between the two bathrooms. From there it rises up to the attic and travels to the other side of the house, then down in the furred space between the exterior block wall and some drywall.

Here is a photo of the exterior of the house. Notice I removed a fascia board for access. [i93.photobucket.com].

Here is a view into the attic from the removed fascia. [i93.photobucket.com]

Here is an interior view of the kitchen. The red line shows the location of the existing pipe behind the drywall.[i93.photobucket.com]

Here is an interior view of the laundry room. Again, the red line shows the location of the existing pipe behind the drywall. [i93.photobucket.com]

My thinking...
1. I read an article about using cpvc pipe for fire sprinkler systems that said cpvc should be kept away from concrete surfaces because concrete is irregular and a high point could rub against the cpvc. To ensure no high spots, I would have to remove all the drywall along the new piping run so I could physically see or feel for high spots.
2. Or, I could remove all the drywall and install thicker furring strips like 2x4's to get enough room so the pipe is off the concrete wall. That's too much work! I'd also have move out all the electrical boxes, etc. In the kitchen I would have to move the countertop too!
3. Or, I could install the cpvc on top of the drywall. May look ugly and be susceptible to damage. In the kitchen I would have to cut into the backsplash of the countertop.
4. Even though I want to get away from copper, I have never had a pin-hole failure in the smaller 1/2-inch copper branch lines. I have no idea why. I've had many in the 3/4-inch copper lines. So I'm thinking hard about just keeping the 1/2-inch copper in the wall and just transitioning to cpvc right after the copper pipe emerges from the furred wall and into the attic (as shown in an earlier photo).

What do you think? Am I missing something?

I would use pex and forget about the cpvc myself…

I considered PEX but nobody seems to use it around here. I heard that other parts of the country use it though.

PEX, also has thicker walls. Hence a 1/2 inch line will have an OD close to 3/4 of an inch.

Best Wishes

pex is copper tube size. THe outside diameter is identical, but the inside diameter is slightly smaller. But another factor to consider is that all your copper should be anchored inside the walls, you will have to tear into the walls to replace all the lines.

I keep visualizing myself walking through the door, and seeing my wife hanging a picture, right through that pipe. She likes to suprise me with her ability to get things like that done.

PEX is what you should use no if ands or butts

Thank you for the ideas. I'd rather stick with cpvc or copper since I am familiar with those materials and I already bought the cpvc.

Besides, wouldn't the pex also wear against the concrete wall. I only have a 3/4-inch furred opening and the concrete wall probably has high spots.

regardless of the pipe material, you need to secure it behind the walls, and make sure there are nail plates on any stud penetration.

Create chases for the CPVC inside the sheetrock. Come down along side the cabinet run and go through the back of the cabinets.It doesn't have to be an eye-sore. You can make it as decorative as you want.