Lawn sprinkler design Information
The most important information that I can pass on to you is " do not be too cheap " in selecting quantity and quality.
Just imagine if your house builder had only installed two light bulbs and one circuit breaker for your whole house. You would be in the dark forever.
Lawn sprinkler design theory is fairly simple and is very similar to the design of electric circuits in your house.
You will need to know the water pipe size that enters your house and the static pressure (water pressure without anything running).
You will need to add the gallons of water used by each sprinkler head on a zone (area or circuit) and not to exceed the total gallons allowed by the size of the supply pipe which are listed in the following information.
The number of and the type of sprinkler heads that you will need to use is determined by the size of the area you need to water and by following the manufacturers recommended head spacing.
I had one competitor tell one of our prospective customers that Genus irrigation installed too many sprinkler heads, I wonder if that contractor had ever read the manufacturers specifications.
Most residential homes in Canada have 3/4" water supplies and can manage 12 gallons per minuet while most residential homes in Costa Rica have 1/2" water supplies and can handle only 7 gpm. A one inch supply can provide 20 gpm with good operating pressures between 60 to 80 psi.
The pressure on the supply line and the amount of water used (gallons per minuet) are very closely tied together. The pressure will drop off suddenly if you design a circuit using too many gallons, it is like using a hose with no nozzle that gives a lot of flow but doesn't shoot very far. Sprinkler heads simply do not work under 20 psi.
There are 3 types of residential sprinkler heads; small sprays shooting from 3 feet to 18 feet using 1 to 3 gpm, medium rotors shooting from 12 to 22 feet using up to 3 gpm and large rotors shooting from 20 feet to 45 feet using up to 4 gpm.
Use the following guide lines and you should be ok with your design as long as the supply pressure is over 40 psi. For a 1/2 " supply use only 5 small sprays or 3 medium rotors or 3 large rotors. For a 3/4"supply use only 8 small sprays or 7 medium rotors or 6 large rotors. For a 1" supply use only 12 small sprays or 12 medium rotors or 8 large rotors and remember not to exceed the total gallons and never mix the type on heads on the same zone.
A good design not only considers the water pressure, gallons used and the size of pipes. It is also very important to consider the lay of the land, try to keep the major elevation levels on separate zones, keep the shaded areas on different zones than the sunny areas and try to keep the shrub or garden areas on other zones than the grass areas.
Think ahead a little in regards to lawn and garden designs and allow for city drops in pressure because new subdivisions lose pressure after all the buildings are complete. Many cities have a number to call for district water pressure information.
Our experience at Genus can save you from mistakes that may happen with first time designs, We would be happy to assist you with any questions that you may have. We can make it easy for you, just send us your landscape plan so we can provide you with an irrigation design or contact us for a complete supply and install quotation.