Irrigation Product Listings & Reviews

Hunter I-20 & I-21 Series Rotor Pop-Ups

Description:

This is a beefed-up version of the PGP designed for the commercial and higher-end residential market. The primary differences between the I-20 and the PGP are that the I-20 has a shut-off feature, a standard check valve, and a stronger spring. The "FloStop" shut-off feature allows the flow to be shut off at the nozzle so you can play with the settings or change the nozzle without getting (as) wet. The check valve prevents the water from draining out of the pipes when the sprinkler system is shut off. This reduces the spitting and spewing of air every time the rotors are turned on. The I-20 comes with a set of 8 standard and 4 low-angle nozzles. Optional high-flow, short-radius, and short-radius-low-angle nozzles are available.

The I-20 series with the standard nozzles are designed primarily for spacings between 25 feet and 45 feet. The purchase of the optional short-radius nozzle set allows the use of a radius between 15 feet and 25 feet, but not on the same valve zone (the precipitation rates will not match!) The I-10 is a shrub model (installs on a pipe above ground). The I-20 is available as a 4" (10 cm) pop-up, a 6" (15 cm) pop-up, and a 12" (30 cm) pop-up. Interchangeable nozzles allow for easy field changes of nozzles. A rubber cover for safety is standard equipment (ALL rotors should come with this!) The arc adjustments are made from the top of the head. Adjustment of the arc is reasonably easy. A optional stainless steel riser sleeve is available. The stainless steel sleeve extends life in tough situations like really sandy soil, but I don't feel is worth the extra cost in most situations. The I-11 and I-21 models are metric versions.

When should you use the I-20 rather than the PGP? I would use the I-20 if you have elevation changes of more than 1 foot in the area irrigated by the valves. The I-20 comes with a standard check valve which will be needed in this situation. You can get the check valve as an option on the PGP, but the cost and effort will probably make it easier to just use the I-20.

Warnings: Do not exceed 45 feet between I-20 rotors, even using the high-flow nozzles! You will need to get the optional short-radius nozzles for the I-20 if you have areas that will require a radius between 15 and 25 feet. If you use the low-angle nozzles watch out, they increase the precipitation rate due to the reduced radius. So if you switch a 3.5 standard nozzle to a 3.5 low-angle nozzle you may get a wet spot. You would use low-angle nozzles in windy areas to keep the water closer to the ground. You would seldom have a need to mix low-angle nozzles on the same sprinkler system with standard nozzles.

Model Numbers:

Manufacturer's Performance Data:

Don't forget Stryker's Law: "Distance between rotor heads in feet should never be greater than the head operating pressure in PSI"! Therefore 35 PSI = 35' maximum spacing between heads regardless of what the chart says!

Recommended nozzle combinations:

The following charts show the nozzles I recommend for matched precipitation rates. I strongly suggest you use these nozzle combinations when designing your system.

It is not possible to exactly match precipitation rates in most cases. You just get as close as possible. Do not throw away the extra nozzles after you finish installing your rotor sprinklers. Keep them. You may find that based on actual conditions you want to go up or down a nozzle size from what I recommend. This type of fine tuning of the nozzles is normal and expected. So if you start to get a dry spot, put a larger nozzle in one of the rotors that waters the dry area. If you see a wet spot developing, then change one of the rotors to a smaller nozzle.

Use the first chart below if you can. If you need a radius not in the first chart move down to the next chart. Example; If the heads on one valve zone range from 18 feet to 25 feet, then will need to use the second chart, "Radius from 17 feet to 27 feet on same valve." (A "valve zone" refers to all the sprinkler heads that are turned on by the same valve.)

You will probably need to use the radius adjustment pins on some heads to prevent over-spray outside the desired watering areas.

Radius from 25 feet to 47 feet on same valve.

Radius from 17 feet to 27 feet on same valve.

Radius from 17 feet up to 47 feet on same valve.

While Hunter claims that the wide range of nozzles for the I-20 allows spacings from 17 feet to 47 feet, the reality is that you can't easily put a 17 foot radius rotor on the same valve zone as a 47 foot radius rotor. To do that, you will need to reduce the radius beyond the recommended limits on many of the nozzles, which will give you less than the best coverage. The chart below is the best you can do in this situation if you really need to do it. However, it would be better if you could put the smaller radius rotors on a separate valve zone using the nozzles in the chart above. (A "valve zone" refers to all the sprinkler heads that are turned on by the same valve.)

For an in-depth description of features found on this and other rotors, see the faq on "How to Select the Best Rotor-Type Sprinkler".