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If I understand your question, I would get rid of the CPVC as early in the system as you can.
Go sch 40 PVC to the backflow preventer. In Houston that is what I would do. We don't get much freezing weather here.

Dan Todd


As you can tell, I just don't like CPVC. PVC Good.

Before I make a suggestion, I'm first going to explain my assumptions so that my suggestion makes scence.

You have 1" PVC or 3/4" copper bringing water from the street to your house. (If it's PVC, it transistions to copper at just outside the house because plumbing codes require metal or CPVC for water lines inside the house... in otherwords PVC is good for direct burial, but not for exposed areas). After comming into the house, it transisions to 3/4" CPVC to distribute in the house.

I would suggest that you either tie into the water line in that small section of copper, or better yet, outside in the front yard. For one, that will maximize your flow capacity. 3/4" CPVC has a smaller inside diameter than 3/4" copper. And if there is 1" PVC in the front yard that you can tie into, then you should have enough capacity that you can feed the irrigation system and not severly impact flow capacity in the house (a 1" pipe can carry twice as much water as a 3/4" pipe). This will also reduce water noise in the house since the water doesn't have to flow inside the house to irrigate the lawn.

Codes don't like PVC pressure pipes in houses, so you'd probably use all CPVC to the backflow preventer. That way, you have no transition to worry about.

Good to know, I get so focused on outside. I really did not think about inside. CPVC is not something I come in contact with much because I am outside.

Thanks

Grasshopper Todd

Quoted from "gh1120"

I have seen some of my neighbors who had PVC (not cpvc) after tapping in running the full length of the basement to exit the other side of the house.

I've seen it as well. It is cheaper than copper by a long shot, but somewhere, it was pointed out that licensed plumbers never use PVC for pressure pipe in houses. I doubt that it makes a big difference. I always preferred copper for not being able to melt and flood a basement, if there was some small fire. CPVC would probably melt as quick as PVC would.