View Full Version : Galvanized Main to CPVC

10-10-2005, 10:26 AM
Well I am starting my next major project of replacing all of the old galvanized water lines in the house. I have started to run CPVC from the main to the water heater and have temporarily tied into the rest of the cold water. Before I get too far I have a few questions.

1. The main itself is galvanized, while I would like to replace it now; that will have to wait for another time. Right now the main is ½” galvanized and I have placed a ½” metal threaded CPVC connection with about 3” of ½ and then transitioned to ¾”. I have read on these boards that CPVC is not comparable to copper…meaning that ¾” CPVC is more like ½” copper and 1” CPVC is like ¾” copper and that ½” CPVC is not recommended.
My thought was to use a ½” copper transaction at the Main then size up to ¾” using copper and then switch over to ¾” CPVC and run that throughout the house.

2. Should I look at running a dual line system? I have the room and CPVC is fairly inexpensive. Does this really make that much of a difference since my main is so small?

3. Back to the sizing issues; when I transfer to the fixtures should I size it to ¾” copper and then down to ½” copper to make the connections or am I safe just reducing down to the ½” CPVC for the last foot or so and then making the connection.

I know a lot of information, but any thoughts or ideas would be great.

Thanks…you guys have always been helpful!

Gary Swart
10-10-2005, 12:22 PM
Forget the CPVC and stay with copper. I'd look at 3/4" main line and then drop to 1/2".

10-11-2005, 10:20 AM
While I think copper might be the way to go, I like working with the CPVC, with as much work as I am doing on the house I would like to keep things simple. Does anyone else have any thoughts? Thanks

Gary Swart
10-11-2005, 02:02 PM
Why not just do what you want to do. No one here is likely to support CPVC over copper, and since it's your house and you're paying the bill do it your way.

10-11-2005, 02:06 PM
1- All plumbing pipes are measured as inside diameter. 1/2" copper is the same as 1/2" cvpc is the same as 1/2" galv. inside......
2- Get the 3/4" as close to the main as you can.......
3- Keep the hot and cold service lines 3/4" right to the last two fixtures then split to 1/2".
4- Then when you run a new water service you will just have to connect.

I would do copper..........

10-11-2005, 03:07 PM
hmmm....I was under the impression from Terry/maybe HJ (http://www.terrylove.com/watersize.htm) that Cpvc had a smaller bore. Anyway thanks for the advice...still not hot on the idea of switching my plans to copper :)

10-11-2005, 04:09 PM
Plumber1. you are correct up to a point. Copper and steel pipes, (schedule 40, since sch. 80 has a thicker wall but the same o.d.), are measured by their i.d.'s. But CPVC, PEX, some polyethylene, etc. are CTS, which means their outside diameter is the same as copper tubing, but since the walls are thicker than copper, the inner bore is reduced in size. AND, if you remember your geometry, the greatest reduction in size happens when you reduce the diameter of a circle, which means that "slight reduction" in size can produce a big reduction in capacity.

10-12-2005, 02:00 AM
You'll be just fine with CPVC . It's good pipe . Run as much 3/4" as you can then reduce to 1/2" . Remember : When copper came out all the guys who had been running galvinized water lines said ," That stuff is CRAP ". They were wrong . CPVC is good pipe , give it a try.

10-12-2005, 07:49 AM
CPVC is "good" pipe until it cracks in a hot attic.