Water pressure determines how far apart your sprinkler heads can be spaced to work properly, and it can also determine which type of sprinkler head is a better choice for your application. Here’s a quick explanation of water pressure – what it is and how the effect it can have on the sprinkler system you choose:
How is pressure measured?
Water pressure is measured in pounds per square inch – also called psi. The average water pressure for most homes and businesses is between 30 psi and 50 psi; most sprinkler systems are designed to use pressures of around 30 psi. You can measure the water pressure at your site with a flow meter or water gauge attached to an outdoor faucet. When determining your sprinkler needs, use the lowest pressure reading to ensure the best functionality.
Spray heads and rotators. Most spray and rotator heads are designed to work their best at about 30 psi. When pressure is lower, the watering radius will be reduced, so you may need to place your heads closer together to get the coverage you need. Higher pressures – those above about 40 psi – will cause the head to mist or fog. Most systems have adjustment valves to help control misting. Pressure regulators installed along the main line can also be used.
Rotors. Rotors are designed to work best at pressures exceeding 30 psi. If your water pressure is already high, a rotor is a good choice for you; if your pressure is low or average and you need a rotor to water your landscape effectively, you can use a boost pump to increase pressure or adjust the spacing of your rotor heads to help make them more efficient.
Drip heads (also called drip emitters). These heads are designed to work best at about 20 psi; high pressures – typically those exceeding 40 psi or 45 psi, but sometimes lower – can cause emitters to break apart.
What if my system uses more than one type of head?
Systems using more than one type of head are designed based on the highest pressure required by the components; valve regulators are often used to reduce pressure to low-pressure heads.
What happens if water pressure is too high or too low?
When pressure is not adjusted properly, your system isn’t going to operate the way it was designed. Pressure that’s too high can result in sprinklers that produce a mist or fog, resulting in water waste and higher operating costs. High pressure can also increase the wear and tear on your system. Some systems can be fitted with special valves that keep the pressure at an ideal level.
Low pressures mean your sprinkler will not be able irrigate the area it’s intended to cover, resulting in dead patches of lawn or garden. For low-pressure lines, boost pumps can often be installed to help increase the pressure to your sprinkler heads.
It’s also important to note that pressure can change along the length of a system, most commonly as the result of a change in elevation: water running down a slope will gain pressure while water running up a slope will lose pressure – generally, about 0.433 psi every foot.
Your irrigation system can be a big investment; if it doesn’t work properly, your budget and your lawn or garden both suffer. Because there are a lot of variables that determine how well a sprinkler system functions, relying on the advice of an irrigation professional is the best way to ensure your system works well for years to come.
The average water pressure for most homes and businesses is between 30 psi and 50 psi; most sprinkler systems are designed to use pressures of around 30 psi.
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.
Without minimum water pressure and flow, fire sprinklers cannot work as intended. They won't be able to put out enough water to suppress fires. If the pressure at a sprinkler head is below a bare minimum of 7 psi, the water won't be able to push out the sprinkler cap when the heat-sensitive bulb breaks.
In general, however, a typical residential fire sprinkler system operates with a water flow rate of around 7.6 to 22.7 liters per minute (2 to 6 gallons per minute) and a water pressure range of around 100 to 175 kPa (15 to 25 psi).
Normal psi for a home pipe system is between 30 and 80 psi. While you don't want the psi to be too low, it violates code to be above 80. Instead, you should aim for a psi that's between 60 and 70.
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.
One of the leading reasons for low sprinkler water pressure relates to the valves on your backflow preventer device. If you notice limited water pressure in your sprinkler system but normal water pressure inside your home, then the problem might be that your backflow preventer valves are not completely open.
On average, a traditional sprinkler system zone boasts five to six rotary heads or eight to ten spray heads. At a minimum, you usually need four or five to cover a small square or rectangle.
Some residential heads will work with as little as 13 gallons per minute (gpm), while others use up to 26 gpm. Commercial sprinklers, not surprisingly, require much more water.
This will result in the remaining water draining into low spots and subjecting the system to freeze damage. Ideal pressures are in the range of 40 to 80 pounds per square inch (psi) for the air compressor with 80 psi being the maximum for rigid PVC pipe and 50 psi for polyethylene pipe (flexible black pipe).
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Water pressure determines how far apart your sprinkler heads can be spaced to work properly, and it can also determine which type of sprinkler head is a better choice for your application. Here’s a quick explanation of water pressure – what it is and how the effect it can have on the sprinkler system you choose: