Minimum operating pressure of any sprinkler shall be 7 psi (0.5 bar).
The pressure requirement varies from 2.0 to 4.0 kg cm-2 with application rate from 4.0 to 20.0 mm hr-1 depending on the nozzle size, spacing etc. Fig. 36.1. shows different type of rotating type sprinkler irrigation systems.
Per NFPA 13 - the minimum end head pressure required for all sprinklers is 7psi. That is just the minimum however. The actual pressure and flow you start with at the end head will be dependent on the spacing of the sprinklers, the required density for the occupancy and the orifice size of the sprinkler.
As per NFPA 15, for a typical water spray system, the design density of spray ranges from 4.1lpm/sq. m to 20.4 lpm/sq. m – depending on the application and hazard type. The minimum operating pressure of any nozzle protecting an outdoor hazard is stipulated at 20 psi (1.4 bar).
The most commonly used residential sprinklers are 4.9 k-factor pendant sprinklers. The minimum pressure and flow for these sprinklers is 7 psi at 13 gpm for spacing up to 16 feet by 16 feet. Hence, the most common demand for two sprinklers flowing is 26 gpm.
For spray heads, it is 30 psi, with an operating range of 15 to 30 psi. For drip lines, this is about 20 psi, with an operating range of 15 to 30 psi. Remember, flow rate and pressure are directly related to one another. If pressure is not well-controlled, irrigation efficiency will suffer.
Impact sprinklers are excellent for low-pressure water sources. This type of sprinkler is built with integrated regulation valves that control water flow. Using impact sprinklers will still allow you to achieve healthy growth of grass and plants, even if the water pressure in your house is less than ideal.
The optimum operating pressure for most residential sprinkler heads is between 30 and 50 pounds per square inch (PSI). With correct water pressure, each head will perform the way they were designed, and the result will be even spray-patterns and efficient use of water.
For a fixed spray system, aim for 20-30 psi per sprinkler. On a rotor/pop-up system, shoot for 30-60 psi. Irrigation and drip systems require 20-40 psi.
For many sprinklers, the recommended operating water pressure ranges between 30-40 pounds PSI. A pressure regulator ensures that water pressure consistently stays within this recommended PSI range, regardless of the water pressure before it reaches the sprinkler.
You can operate 2 or 3 sprinklers at one time with 'Y's and extra hoses, depending on your water pressure. To run more than one sprinkler off the same faucet, attach a 'Y' to your faucet and run a hose to each sprinkler.
Newly installed sprinkler systems must be hydrostatically tested to check for leaks at a pressure of at least 200 psi (14 bar) for a period of at least two hours. When existing systems are modified such that the work affects fewer than 20 sprinklers, the system only requires testing at the system working pressure.
If your home's water capacity was 10 GPM, you could place 3 heads per zone. Consult the Performance Charts on or inside the box your sprinkler head came in for your head's exact performance data, or locate the performance data in the Support area of this website.
You need pressure regulators to achieve the intended distribution pattern and application rate. If you do not control the system pressure, it can negatively affect the sprinkler performance. Without regulators, the throw radius can alter, fitting, and emitters could even take damage or blow out of the tubing.
The average usage of water in a residential sprinkler system is between 12 – 30 gallons per minute depending on the type and size of the sprinkler head.
A common rule that is followed for obstructions within 18 inches of the sprinkler deflector is the “three times rule”. This requires sprinklers to be positioned away from obstructions a minimum or three times the maximum dimension of the obstruction.
The sprinkler pipe size from the water supply source to a sprinkler shall be not less than 3/4 of an inch (20 mm) in diameter.
Generally, the larger a pipe is, the higher the water flow. The water pressure level always has to be taken into consideration, however. Even the biggest, smoothest pipes will not have effective water flow if the water pressure is low, because there is not enough strength to defeat the force of friction.
A Water Regulator Valve May Be Needed to Save Water
If the water pressure level coming into your home from the city exceeds 80 psi, you need a water pressure regulator. Reducing the system pressure 10 to 20 psi can save thousands of gallons a year in the typical home.
They vary in reliability and ease of operation, but the main problem with tap timers is that they reduce water pressure, which cuts down on the number of sprinklers or drippers you can successfully operate.
NFPA 13 establishes a minimum pressure of 7 psi, even when the calculation procedure yields a smaller value. This ensures that sprinklers produce the correct spray pattern. However, the NFPA 13 also provides exceptions to the method, which are covered in Chapter 7.
Ordinary Hazard 1 and 2: Coverage area of 130 square feet per sprinkler head; 15-foot distance maximum between sprinklers. Extra Hazard 1 and 2: Coverage area of 90-130 square feet per sprinkler head, based on certain factors; 12-foot distance maximum between each sprinkler head.