SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

I'd upsize to 1" poly or pvc. If your in a cold climate were the system is blown out every year I'd use poly pipe.

If your able to, start with new 1" pipe from your new valve.

if depends on your sprinkler service size. is the service that is going to your sprinkler system 3/4" or 1". it is usually on or the other. whatever the size you will lose no pressure or flow by sticking with the same size. in other words.....if your sprinkler main and manifold are 1 inch.....stick with one inch. if it is 3/4.....you can safely stick with 3/4. but using 1 inch like tom suggested is a good way to go even if it is 3/4 inch service. i inch fittings and pipe are the way to go these days with the availability of products. but just to clarify it wont make any difference sizing up to 1 inch if you are working from a 3/4 inch main as far as pressure and flow are concerned. my company always uses one inch regardless becuase it is more common and with new houses all having 1 inch service it is just better to stick with one size for both. tom is right to tell you to use poly pipe as it is more resilient to freezing. also a whole lot easier to work with. check with your local code though. some areas demand you use pvc.

Good explanation lush

If you decide to use poly pipe check out Tom Kings Blazing Saddles, they are quick and easy.