Question
We've installed an sprinkler system and are having trouble with pressure. Because we live in the country we had to run a water line for about 1 mile; we used 1.5 in. PVC pipe for this and reduced it to 3/4in. PVC about 500 ft from our home. When the sprinkler system was installed, 1 in. PVC pipe for the main line was installed to the 3/4 in. pipe meter line and then reduced to 1/2 in. PVC pipe near the risers. We have 55 PSI to run our house and have .183 gpm. We also have 6 valves for the sprinkler system and 36 sprinkler heads (6 sprinklers/valve). I am under the impression we went wrong with using the 1 in. PVC from the 3/4 in. main line. Can this be corrected and how? Can a booster pump be used, and if so, what is recommended?

Answer
Hello Emily, I hope this helps. I'm going to try and keep this as simple as possible, you have alot going on. First of all, for every foot of pipe you run, you have pressure loss. The "bigger" the pipe you run, the less pressure loss you will have. First thing I would recommend is continuing the 1.5 inch line all the way to the house. Your losing alot of pressure in that 500 ft. of 3/4" PVC. Second thing that a sprinkler is designed on besides pressure, is volume. You say you are only getting .183 gpm? Gpm stands for gallons per minute. Lets say you open up a hose bib, how much water will come out of the outlet in one minute. If you're only getting .183 gpm, that means you're only getting less than 1/5 of a gallon of water in a minute. This sounds awfully low. Most sprinkler heads put out anywhere from .5gpm to 4 gpm. Lets say you're using a spray type of head, these heads throw from a 8 ft. radius up to a 15 ft. radius. A head that throws 12 feet but is only a 90 degree pattern will put out about .5 gpm, but a head that throws 15 feet in a 360 degree pattern might put out 4 gpm. By finding out how many gpm each head uses, you can determine how many gpm each valve is using. I think where you are getting confused, is in the pipe sizes you are using. The bigger the pipe size, the more pressure and volume you will create. Think of it as putting out a fire on your house, would you rather use a 1/2 pvc line, or a 2" fire hose? You want as much volume of water as you can get. It is actually better to go up to 1" at the main, because you will have less pressure loss. You also should have kept your lateral lines (lines to the sprinkler heads) up to at least a 3/4" size fom the valves through the first 4 or 5 heads. Just a quick note on pipe sizing, on 1/2" pvc you can figure about 5 gpm, on 3/4" pvc you can figure 12 gpm, on 1" pvc you can figure on 20 gpm, depending on your pressure. First thing to check, is how big of a meter, your county has put in for you. Probably either 5/8", 3/4" or 1". On a best case scenario, if it's a 5/8" meter figure maybe 8 to 10 gallons per minute, 3/4" 10 to 12 gpm, and 1" 16 to 20 gpm. The first thing to try, is turn off the water meter.Find the end of the 1.5 inch line before it goes to 3/4", and cut it. Temporarily stick a elbow on it and bring a piece up to the surface. Turn the meter back on, and calculate by watching the meter, after 1 minute, how many gallons the meter has put out. If it's running 10 gpm or more, than you can probably design a system to work, without putting in a pump. You could probably get the same volume at the house by continuing the 1.5 inch line. If your volume at the end of the 1.5 inch line is 8gpm or less, you probably need to install a pump. Not knowing what kind of heads your using, or how many gallons per minute each valve is using, it's a little hard to figure a pump size. Normally a system is calculated any where from 12 to 20 gpm, per valve, at anywhere from 60 to 80 psi. Once you figure out how many gallons per minute each of your valves are using, get a pump accordingly. Keep in mind, if you still only have 1/2" pvc to the heads, you're only going to get about 5 to 7 gpm, no matter what pump you get. If you need anymore help on figuring your gallons per minute for your heads, or have any more questions, just let me know.Hopefully I've explained things in lay mans terms. If I'm not clear enough on my answer, just let me know. Thanks and have a great day.