I need to replace a manual 3/4" anti-siphon valve. Do I have to cut the existing pipes (both pvc) and attach new threaded adapters to install the valve? It doesn't appear that there is any way to unscrew the old valve.

yeo - when you go to twist it off it will tighten on one end while loosening on the other end -- if there is enough 'give' to the pvc, you may be be able to flex it enough but this will weaken exisitng joints for future possible issues. Not to mention now you have to get the new one on..... cut one end for best results.

Let us know how it went.

I have a leaky valve and figured I could DIY it. I bought a Rainbird anti-siphon electric valve with 2 threaded female attach points. My question is, do I have to cut the supply and zone pipes (both pvc) and attach new threaded adapters to install the valve? It doesn't appear that there is any way to unscrew the old valve. Thanks in advance for the help.