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

Sixteen zones? For a simple solution, install a brass master valve you can trust, and the pressure stops there. If you need to open some remote faucet on the mainline for water, you can turn on the disabled zone to pressurize the mainline. I know of one brass electric valve that will have a minimal pressure loss, due to its special design and solenoid. It will cost you more than $250

But basically, this sounds like a screwed-up system, if it's using such a wide range of flow-rates, with some of it not being backflow-protected. By the way, the maximum rated flow for a one-inch water meter is supposed to be 50 gpm, according to AWWA standards.

The real solution is to break it down into more evenly matched zones that can run at lower pressures, and to regulate the pressure upstream of the entire system. Also, if the property runs uphill from the house, you should know that the PVB only provides backflow protection for those sprinklers that are lower in elevation than the PVB. The one device that can protect the entire system, at any and all elevations, according to California code, is an RPZ device. An RPZ has a 10 to 15 psi pressure loss, so making the system right will require some reconfiguration, if some zones are really marginal. Often, you can swap out sprinkler-head nozzles, and balance things out.

A 1½ inch meter has no problem supplying the 75gpm you mentioned. Now, if adding atmospheric vacuum breakers can be done, with the needed elevation above the sprinkler heads they require, that can put the entire system under proper backflow protection. The only other problem I see is how a master valve would be located, if part of the system is fed through a PVB and part of it is fed around it. Nothing a PVB feeds can be within a foot of elevation of the PVB. You cannot have any pipes running uphill from it.

I would still be looking at the possibility of swapping nozzles on rotor heads, if doing so would reduce the flow in the marginal zones (while maintaining coverage) - as far as pressure drop goes, reducing flow rates where you can will allow for some headroom for changes, and maybe even pressure regulation.

You should really locate any missing pieces of the system, especially the line that feeds the four zones that aren't backflow protected. You would like to have a common shutoff for the entire system, and maybe even common backflow protection and pressure regulation.

As for pressure loss for a master valve, you can do much better than 8 psi. The mix of high-flow and low-flow zones on one line force you to use a valve that doesn't have a minimum flow requirement. Standard valves don't have this capability. Nothing sold by Rainbird or Hunter does. You have to stray out of the usual to get a valve that doesn't have a minimum flow requirement. Once you find one, you can use a large enough one to keep pressure loss to a minimum. In your case, with a 75 (or even 50) gpm flow, you'd be using a 2 inch valve, and bushing down the inlet and outlet, if need be. Same thing if you need to put an AVB onto the 75 gpm zone. You'd use a 2 inch one, regardless of the smaller pipe sizes it may connect to.

Before I'd be paying over $250 for what is almost surely a special-order valve, I'd be trying to rework the system to reduce flows and get some extra pressure for the marginal zones. If you could manage to get the flow down to 30 gpm tops, you'd have a much healthier system. Too much water rushing through too small a pipe results in surge pressures and water hammer that can make perfectly good valves into leakers. The Hunter controller can supply power for additional zones, if need be, by adding a module, and it looks like you have a zone or two you aren't making full use of.

Give the whole system a good hard look before you spend more money on it.

For 6-foot-wide strips, there aren't many, if any, nozzle choices. Hunter center-strip nozzles claim a 5x30 pattern, and might do more with higher pressures. Keep working at reducing flow, where possible. The zone with just a couple of heads might be able to be switched over to another existing zone, if the watering times permit. The ICC controller can handle the electrical load of two zone valves at once, along with a possible future master valve. 30 gpm is the target I gave based on the pipe sizes you mentioned. The more you can reduce the system flows, the less water hammer the valves will get, and the more pressure headroom you will have for future changes. Especially if you install a master valve and an RPZ. Lower flows might allow a more economical size of backflow preventer.

Could the homes have been models?