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

No problem - you can use antisyphon valves for your zones. A pro wouldn't guess at the amount of water, though. He would employ a flow-and-pressure tester to know exactly what the supply was.

Trying to tap of a 1/2" copper is VERY limiting.

For starter, the plumbing rule of staying under the 5fpm speed limit means that you will ALWAYS be limited to a maximum of about 4gpm per zone.

The next issue is that some people find the noise of running water when the irrigation system is running to be objectionable (hence the reason to tie in before the plumbing enters the house).

The other possible issue is pressure loss. As water flows through a pipe, it loses pressure as the result of "friction" with the pipe. The narrower the pipe, the faster the water flows and the higher the friction losses. As an example, 100ft of 1/2" copper running at 3gpm will lose about 10psi just from flowing through the pipe. But if you simply upgrade to a 3/4" copper pipe, the pressure losses are cut in 4th (i.e. 2psi for the same 100ft run). So when it comes to pressure losses, a small change in pipe size can make a huge difference.

If your only worry is dealing with going under a sidewalk... then don't be. Go under the sidewalk. It's not that difficult. If you have very loose soil, there is the old garden hose trick of just drilling a hole with water. If you have a more clay like soil, all you need is a piece of rebar and black pipe and a sledge hammer, simply pound a hole under the sidewalk (the rebar makes a great pilot hole, then get a piece of 3/4" black pipe with a 3/4" to 1/2" reducer on the front and top the reducer off with a nipple. The resulting hole should accomidate 1" PVC).

Now if you were having to go under a driveway (and I've done that too), I would say that's a whole different thing to consider. But getting a piece of pipe under a standard sidewalk is well within the capability of a DIY.

Even in my worst case (5' wide sidewalk with large rocks under it needed a 3" hole), I got the job done with no problem renting a pressure washer (make drilling through rock-filled clay child's play).

With irrigation, there is supposed to be overlap... basically every spot in the yard should be getting water from two head. It's known as head to head coverage and it's what you want regardless if you want to use sprays, rotors, or the MPRotators.

My personal thoughts are that you get the MP2000 Rotators. Under ideal conditions, they throw water 20', but realistically 16' to 18'. They are supposed to be adjustable down to 13'. I personally would run a set of the MP2000 Rotators in each corner and along the sides spaced 15' apart. That will give you plenty of overlap, and you could do the whole area on a single circuit. From what I calculate based on these spec sheets (http://www.hunterindustries.com/products/mprotator/) the zone would require 3.5 to 4.0 gpm of flow and only needs 30psi at the heads.

To get consistant results, I found the MPRotators in my yard worked best with the spray bodies with the pressure regulators built in.