Piping is the most permanent and the most important factor affecting sprinkler system performance. You can change heads or timer easily, even change valves. But once the piping is in the ground, nothing is going to change it, so it better be right. If you are using one of our piping plans, you should have no problem. If not, you should make sure your piping is sized properly to provide even pressure at the base of each sprinkler head. In our "bigger is better" society, many do-it-yourselfers think they are actually improving performance if they use all 1" pipe, rather than bothering with that "little 3/4" and 1/2" stuff. Unfortunately, nothing could be further from the truth. Facts are that sprinkler systems need to be piped to correct plumbing (hydraulic) theory. If pipe is sized correctly in a sprinkler system, each and every head will have equal pressure, will spray just as far as any other head, break up just as well, and water just as effectively. If all one size pipe is used, the head furthest from the water source will have the greatest pressure, while pressure reduces as we get closer to the water source, until we reach the closest head to the water source, which will have the least pressure. If you have ever seen a system where most of the heads seem to throw water great, while one or two heads on that same station just don't seem to have much pressure, don't spray very far, seem weak, you were looking at the results of all one size pipe. When planning your system, plan the piping and plan it right, because if you don't, things are not going to work exactly the way they should. Piping correctly is easy; each head has a factor of water usage. Most small pop-up spray heads with 12 foot standard nozzles use 1 gallon per minute for half circle, two gallons per minute for full circle. Double those figures for 15 foot nozzles. Most rotor heads use 2-4 gallons per minute, depending upon nozzle size. When you plan a zone using irrigation grade pvc pipe, you can figure 0-5 gallons per minute through half inch pipe, 6-10 gallons per minute through three-quarter inch pipe, and up to 20 gallons per minute through one inch pipe. If you are using a city water meter, you are usually limited to 12 gallons per minute. If you aren't fond of technical planning, you can still size pipe acceptably using a seat-of-the-pants rule-of-thumb formula; piping from the water source connection to your solenoid valves should all be one inch. From the solenoid valve to the first head on the watering station should be one inch pipe, then use three-quarter inch pipe to the remaining heads, but install the last two heads using half inch pipe. It's not perfect, but it will work a helluva lot better than all one inch pipe and be a lot cheaper to install. The alternative is for some heads to throw correctly, while some don't have pressure enough to spray very far or break up properly into droplets. All of the above information is predicated on using a standard size city water meter as your water source, which usually supplies 12 GPM water flow at adequate pressure for irrigation. If you have a well, the water supplied can differ racically, and you should determine the capacity of your well prior to any design or installation activities. Once well capacity is determined, you can proceed. Ideally, you will place your flags in the ground where your heads will be located, then draw a quick diagram of where your heads are located and how your piping will go. Then you will start at the furthest head on each watering station and work your way towards the solenoid valve, adding up gallonage demand and sizing the pipe as you go. Note how we have done this on the spray head piping and the rotor head piping in the above example. You will note we also went to three-quarter inch pipe on the rotor watering station at a point where we only had a 4 and one-half gallon per minute demand. We did this because experience has taught us that rotor heads need a little extra water for flushing when they pop and retract, so on rotors stations we go to three-quarter inch pipe at four and one-half gallon demand, in fact our house rule is never to feed more than one rotor head with half inch pipe. if you have two rotors, you go to three-quarter inch pipe. Another cardinal rule... never mix spray heads and rotor heads on the same watering station. Why? Because the small spray heads precipitate at twice the rate of rotor heads, putting down double the water in the small areas they cover. This is why most sprinkler contractors instruct their customers to run a rotor head watering station for twice the length of time you run a small spray head watering station. That way, both watering stations are putting down equal amounts of precipitation. Note - Our design-piping drawings are also available without purchase of materials - $25.00 per drawing including instructions System Design Drawings currently available: |
