Rainbird sprinklers come in a variety of models and sizes that provide different gallon per minute (GPM) flow rates. The gallons per minute rating refers to the amount of water that flows through the sprinkler head per 60 seconds of operation. This measurement helps determine how much area a sprinkler can cover and how long it will need to run to provide adequate watering.
Typical GPM Ratings for Residential Rainbird Sprinklers
For residential lawn and garden use, some common Rainbird sprinkler GPM ratings include:
- Popup spray heads – 1.5 to 2.5 GPM
- Rotary sprinklers – 2 to 8 GPM
- Impact sprinklers – 3 to 12 GPM
- Gear drive rotors – 2 to 15 GPM
- Rotary nozzles – 0.5 to 2 GPM
Popup spray heads and rotary nozzles are lower output designs intended for watering flower beds, shrubs, and smaller areas that need less water volume. The higher output rotors and impact sprinklers can cover larger zones like full lawns and turf areas.
Factors That Determine Flow Rate
There are several factors that determine the gallons per minute rating for a Rainbird sprinkler model:
- Sprinkler type – Spray heads, rotors, and impact sprinklers are engineered for different flow rates. Rotors tend to have higher GPM while spray heads have lower output.
- Nozzle or orifice size – Larger water passage openings allow more water flow. Nozzle sizes are often adjustable on Rainbird products.
- Operating pressure – Higher water pressure enables more flow through the sprinkler. Pressure regulates the exit velocity.
- Arc adjustment – Partially reducing the arc of coverage on an adjustable sprinkler lowers the GPM rating.
Typical GPM of Commercial & Agricultural Rainbird Sprinklers
For large scale landscape irrigation, agricultural, and commercial applications, Rainbird makes high flow rate sprinklers measured in hundreds of gallons per minute. Some examples include:
- Big Gun impact sprinklers – 200 to 1,200 GPM
- Rainger rotors – 60 to 550 GPM
- Falcon rotators – 60 to 330 GPM
- Rain Curtain nozzles – 12 to 50 GPM
These heavy duty sprinklers can cover extremely large areas like golf courses, parks, sports fields, and farm crops. The high flow allows them to project long distances and uniform distribution.
Checking GPM of an Installed Sprinkler
If you need to determine the actual flow rate of an existing sprinkler that is installed in the field, there are a couple methods to check gallons per minute:
- Check the product model stamp – Most sprinklers will be marked with the manufacturer model and flow rate. This is the easiest way to find GPM.
- Time the fill rate – Place a 5 gallon bucket under the sprinkler and time how long in seconds or minutes it takes to fill to the 5 gallon mark. Then calculate the GPM based on the fill time.
- Flow meter – Use an irrigation flow meter gadget or tool that attaches to the sprinkler head to measure GPM digitally.
Converting Between GPM and GPH
Flow rates for sprinklers are commonly expressed in gallons per minute (GPM). But sometimes you may need to convert GPM to gallons per hour (GPH):
- To convert GPM to GPH, multiply the GPM by 60. For example, 5 GPM x 60 = 300 GPH.
- To convert GPH to GPM, divide the GPH by 60. For example, 320 GPH / 60 = 5.33 GPM.
Comparing Rainbird GPM to Precipitation Rate
The gallons per minute rating of a Rainbird sprinkler correlates closely to the precipitation rate – how much water is applied per hour over the coverage area. But precipitation rate also accounts for the spray pattern and spacing.
A sprinkler with a higher GPM will be able to apply more precipitation. But the precipitation rate calculation looks at how a sprinkler with a defined spacing and pattern distributes the flow over an area. So GPM is not always an exact indicator of precipitation rate.
Using GPM to Determine Run Times
Knowing the gallons per minute of Rainbird sprinklers allows you to properly set irrigation run times to deliver adequate water for your landscape. The steps are:
- Identify the GPM rating of the sprinkler heads.
- Determine the square footage of the irrigation zone covered.
- Choose an appropriate precipitation rate based on plant type and soil (e.g. 0.5″ per hour).
- Calculate the gallons needed per zone based on area and precipitation rate.
- Divide the gallons needed by the sprinkler GPM to get the runtime in minutes.
Checking your work with catch cup tests is recommended to dial in run times. But understanding the sprinkler GPM and zone details takes the guesswork out of programming watering schedules.
Comparing Different Sprinkler Types by GPM
When designing an irrigation system or selecting components, considering the GPM can help choose the right sprinkler make and model for each portion of the landscape. Some key comparisons:
- Spray heads – Excellent for smaller zones like gardens. Lower GPM reduces overspray and runoff.
- Rotors – The go-to for full coverage of lawns and open areas. Moderate to high GPM depending on model.
- Impacts – Flexible GPM range capable of handling large turf zones or agricultural fields.
- Nozzles – Lowest GPM of all types makes them ideal for water conservation.
Also consider adjustable arc sprinklers to reduce GPM as needed. And utilize zone dividing and valves for sprinklers that have mismatched GPM capabilities in the same system.
Comparing GPM of Same Model with Different Nozzle Sizes
Many Rainbird rotary sprinklers and spray bodies accept interchangeable nozzles that alter the flow rate. For example, the 5000 series rotors can be fitted with a range of nozzle sizes from the #4 at 2.5 GPM up to the #32 at 14.7 GPM per head.
With nozzles, the smallest size produces the lowest GPM and precipitation rate. Moving up sequentially to the highest number increases the GPM output. This allows flexibility in using the same sprinkler bodies and modifying only the nozzles to adjust water volume as needed.
Factors that Reduce Effective GPM
When evaluating Rainbird sprinkler GPM, be aware that the published flow rates assume ideal conditions. In the real world, there are factors that can impede flow and reduce the effective GPM:
- Friction loss in pipes and fittings
- High elevations and non-optimal water pressure
- Bends and angles in piping
- Smaller diameter supply pipes
- Clogged or dirty sprinkler screens
- Partially closed control valves
Accounting for losses, plan for about 10-15% lower actual GPM versus the rated spec for the sprinkler model under real conditions.
Typical Sprinkler Spacing Based on GPM
The gallons per minute rating of Rainbird sprinklers also factors into proper spacing between heads. Typical maximum spacing guidelines based on GPM are:
GPM Range | Maximum Spacing |
1 – 2 GPM | 12 – 15 feet |
2 – 4 GPM | 15 – 18 feet |
4 – 6 GPM | 18 – 21 feet |
6 – 12 GPM | 21 – 30 feet |
12+ GPM | 30 – 40+ feet |
Higher GPM heads can be spaced further apart while lower flow sprinklers need to be closer together to achieve head-to-head coverage. But optimal spacing still depends on the spray pattern and other attributes of the nozzle or rotor design.
Overcoming Low GPM in a Zone
There are situations where an irrigation zone contains sprinklers with mismatched GPM capabilities from different models. This can make it tricky to set runtimes. Strategies to handle low GPM heads in a zone include:
- Group the heads into separate zones based on GPM
- Install a flow control valve for each head to even out precipitation
- Replace all heads to use matching GPM models
- Accept less efficient coverage in that zone
The best remedy is to segregate standard rotors, spray bodies, and low volume heads into their own valves and program settings. Then runtimes can be tuned appropriately per zone.
Benefits of Understanding GPM
Taking the time to learn and consider the published gallons per minute ratings for Rainbird sprinklers enables:
- Choosing appropriate sprinkler types and models for each use case
- Even water distribution based on proper spacing of heads
- Accurate programming of zone run times to prevent over or under watering
- Balancing the precipitation rates across different zones
- Plan smart automation schedules according to each area’s needs
- Troubleshooting problems with pressure, spacing, nozzles, or programming
In summary, GPM plays an integral role in designing, installing, and managing an efficient irrigation system. Check your Rainbird sprinklers’ specs and utilize the flow rates to make informed decisions.
Conclusion
The gallons per minute (GPM) rating specified by Rainbird provides valuable insight into the flow capabilities of their various sprinkler models. Whether you are choosing rotors, spray heads, or nozzles, the GPM indicates how much water volume can be delivered to the landscape over a given time period.
Knowing the GPM rates aids proper spacing, zone configuration, setting runtimes, and troubleshooting irrigation system issues. Combined with understanding of pressure, patterns, and precipitation rates, the GPM helps ensure even coverage and efficient watering based on your specific landscape needs. Checking your Rainbird sprinklers’ flow rates against the published specs is an important data point for effective system operation and water management.