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

After the valve, you need to install a 150 mesh (or finer, i.e. higher number) filter. Since the pressure is already below 50psi, it sounds like you can skip adding a pressure regulator.

Next, run 3/4" PVC underground from the valve/filter to where the drip irrigation is needed. The way I like to come up out of the ground with drip is to transition from 3/4" PVC to 1/2" with a 3/4-1/2 threaded bushing. I then transition to 1/2" copper (connecting the 1/2" bushing to a 1/2" female copper fitting with some sort of double female threaded funny pipe). After about 12-18" of copper, turn 90 to go up and break the surface, and another 90 at the surface directly into another copper female. Then I connect the drip irrigation to the copper female (use either a special purpose fitting that will transition from 1/2" pipe thread to your drip line, or get a 1/2" male threaded x male slip fitting).

That way, the parts of the drip irrigation exposed above ground are rugged copper (able to withstand things like feet and weed wackers... espeically if the line runs up the outside of a containter). The delicate PVC is protected under ground, the copper should last forever (or until a car runs over it) and if the drip irrigation goes bad, you can rip it all out back to the copper and start over as needed.

I use a Toro EZ flow 2604 valve for my drip line without any problems. You basically need a valve that can handle low flow and pressure so that the valve can open/close properly. The 2604 has a Flow range of 0.25-30 GPM and an Operating pressure of 10-150 PSI which should work well for most drip lines.

You can use anything from 1/4" polytube all the way to 1" polytube. Most homeowners will use 1/2" polytube as a mainline but it really depends on how much water you need to irrigate. Since you already have poly laid I would stick to that and transition that to the ½ and ¼ drip tubes as needed.

Look over some of the drip tutorials; they were very helpful for me when I planned my drip system.
http://www.dripirrigation.com/drip_tutorial.php

http://www.irrigationtutorials.com/dripguide.htm

Given that the valve can operate up to 30GPM, it will not be an issue feeding drip irrigation.

Instead, the sort of issues you'll face is limiting the length of the drip tubing so that the pressure doesn't drop too much from one end of the tubing to the other, otherwise plants closer to the valve will get more water that those at the end of the tubing. But you have to get into lengths over 100' before that becomes an issue.

If you are using the little emitters that put out at a rate of 1/4, 1/2, 1, or 2 GPH (that's gallons per HOUR) then a filter is required. As for which, doesn't mater as long as it has a filter of 150 mesh or finer. Same thing with tubing, it generally doesn't mater what tubing you use, but because each manufacturer makes their tubing a little different in size than the next guy, what ever tubing you buy you will likely need to use that manufacturers couplers (unless you find some universal couplers... rainbird makes something of a universal fit coupler system).