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

Using larger pipes reduce pressure losses. There is nothing wrong with using 3/4" components with a 1" water line. Usually, the smaller components will have more of a pressure loss than the larger components because of the increased restrictions. But that's about it. And even that rule doesn't always hold, especially with RPZ backflow preventers (i.e. depending upon the GPM you are designing for, it's possible to get MORE pressure loss through a 1" RPZ than you will get through a 3/4" RPZ).

Consider it this way... the sprinkler valve you are likely to use will likely have a hole that is about the diameter of a standard pencil that all the water must flow through. This will be the case whether you are using a 1" valve or a 3/4" valve. Acctually, it's even possible that the "guts" of the two sized valves will be identical. The main reason the manufacture makes the valve in 3/4" and 1" sizes is so you can get the valve to match your pipe size without having to add a reducing bushing.

I too have a combination of drip and conventional sprinklers. I'm using the Rainbird DVF (or it's equivilent) for both applications just fine. Actually, I've got one circuit that has a single drip emitter that is likely only puting out about 3gph (that's 0.05 gpm) and the valve is working just fine.

As for the RBY, that is what else where is called a Wye filter (because of its shape). When doing drip irrigation, you HAVE to have a fine mesh filter to make sure there basically isn't ANYTHING in the water because the drip emmitters will instantly clog up on the smallest of particals. And even if you are on city water, there will still be "stuff" (including fine grains of sand) that will clog the drip system. Actually, it will improve the life and reliability of your entire system to include a Wye filter between the meter and the backflow preventer. That will prevent "stuff" from getting in the backflow preventer as well as make sure fine particals don't get trapped in the valves. As an example of why you need to include a Wye filter is what I found in my system after the 1st year of use. I am on city water, and based on the annual reports we get, our water system is above average. But the first time I cleaned the filter, I found a splinter of wood about the diameter of a toothpick about 1/4" long in the filter. Something that big would easily clog any drip emmitter, and likely even a control valve. However, if you include a filter before the valves, you have to make sure it is compatible with a mainline (constant pressure). Generally, that means the filter must state that it can withstand pressures to 150psi. Here is an example of Rainbird filters: http://www.rainbird.com/drip/products/control/prfilter.htm However, I would recomend against the filter/pressure regulator combo. What you want (to minimize components) is seperate filter and pressure regulator. That way, you can use the filter before the backflow (if you used the pressure regulator there, the pressure coming out of the backflow would be something like 25psi) but then split the mainline between the "regular" valves and the "drip" valves. Then insert the pressure regulator to the mainline leading to the drip valves. (Here we go, here's the rainbird Wye filter by itself http://www.rainbird.com/drip/products/control/inline_wye.htm and the inline pressure regulators http://www.rainbird.com/drip/products/control/inline_reg.htm. The problem you can run into is that so many people just skip filtration, that it's difficult to locate them. (Well, it took a little digging, but I found then here at our sponser's web site... they were under the drip section, not the filter section http://www.sprinklerwarehouse.com/Drip-Irrigation-Filters-Screens-s/1046.htm). BTW, the larger the mesh number, the smaller the holes. For protecting the drip irrigation, you want the 200# NOT the 80#.

I don't think there is much the city can (or will) do. From what I understand, cities are only required to supply you with something like only 35psi of water pressure. At 45-50, that's well within the likely requirements of the city.

Where did you test the static pressure? Are you sure it wasn't AFTER a pressure regulator? Most homes (where pressure regulators are needed) are setup such that they have one hose spigot before the pressure regulator and one after the regulator. The regulator will usually be preset for about 50psi (and usually require something like a minimum of something like 15psi between the incomming pressure and the regulated pressure.

But even if you only have 45psi and you have to go through an RPZ (that will steal another 12-15psi), that should be enough to still install a system. It's going to be pushing it, but possible. There are a couple of sprinklers that can operate at only 25psi. One thing frequently used when low flows are required is MPRotators. You use standard Rainbird spray bodies, but replace the nozzle with the MPRotator. I seem to recall that @25psi, the MP2000 will throw water about 17'. You might have to design several zones, but it's possible with only 5gpm.

Try to look on the bright side, if your pressure readings are right, sounds like you won't have to worry about a pressure regulator for the drip stuff.