Irrigation - Design
|The design of your irrigation system is the most technically complex part of any landscape or garden. For owners and landscape professionals alike, the recommendations below tell you how to comply with the City Standards.
Low Water Use
To keep your system consistent and manageable, it is recommended to use
one type of sprinkler head throughout.
- Keep sprinklers, drip irrigation and bubblers on separate valves. Mixing
flow rates effects uniformity.
Pressure and Valves
- Acceptable Low Flow Valves, Filters and Pressure Regulators
Pressure regulation is important to insure that the dynamic pressure at
each emission device is within the manufacturer’s recommended pressure
range for optimal performance. Pressure regulation may include a single
master filter and/or master pressure regulator may be used for the
entire system, located after the backflow device and/or master valve. In
this case, if the system does not include a master valve, heavy-duty
grade filters and pressure regulators that can tolerate constant
pressurization must be used.
- Spray heads with or without multi-stream, multi-trajectory
rotating nozzles, must have built-in pressure regulation in the body or
stem or pressure regulating swing joints. All sprayhead bodies should have pressure regulation in the actual
- Low head drainage is prohibited. Use anti-drain valves or check
valves in sprinkler heads and drip emitter devices where necessary, like
at the base of a slope.
- Put a manual shut-off valve (such as a gate valve, ball valve, or
butterfly valve) as close as possible to the point of connection of the
water supply, to minimize water loss in case of an emergency
(such as a main line break) or for routine repair.
- Make sure you have sort of backflow prevention device on your irrigation
system to prevent water from the irrigation system contaminating the
domestic water supply.
Manual shut-off valve
Depth and Spacing
How deep to bury pipes? See chart on page 10 of the City's Water-Efficient Landscape and Irrigation Standards . Remember above grade pipe must be sch 80 or metal, and typically sch 40
is used for below grade.
- Sprinklers cannot be located within twenty-four inches (24”) of any
trees or impermeable hardscape, including but not limited to sidewalks,
driveways, alleys, streets, walkways, fencing. See the Overspray page for compliance strategies. The Subsurface Watering Systems
page has links to several professional system solutions.
- In order to get head-to-head coverage with your sprinklers, make sure
your design takes in to consideration proper sprinkler spacing based on
pressure and nozzle type.
Determining proper depth
Drip Irrigation and Bubblers
Drip irrigation is required for all plants one-gallon or larger in
size, with the exception of trees. Use drip systems with emitters
that do not exceed 2 gph.
- Drip irrigation valve assemblies should have A BACKFLOW PREVENTION DEVICE, A FILTER with a 150 – 200 mesh and a wye or tee filter with a stainless steel screen,
AND A PRESSURE REGULATOR.
- For backflow prevention devices use an anti-siphon valve or some other master backflow protection device, like a pressure vacuum breaker or reduced pressure zone device.
- In-line remote control valves can only be used if there is a master backflow prevention device at the Point of Connection.
- A master pressure regulator, and a master filter may be used at the point of connection in lieu of regulators and filters at every valve assembly.
- Multi-outlet drip emitters are prohibited; ¼ inch or 1/8 inch tubing is
only permitted on container Plantings and Raised Plant Beds.
- When specifying bubblers for trees remember that bubblers emitting 0.5
gallons per minute or less may be used for 24" box trees and they must be on a separate valve.
- When specifying bubblers for vines remember that bubblers emitting 0.25 gallons per minute or less may be used and they must be on a separate valve. Bubblers may be installed above or below grade but runoff is not permitted.
Drip-tubing with stakes
Water Features, Fountains, Ponds
When designing fountains, ponds or other decorative water features in
the landscaped area, excluding swimming pools or spas, keep the total
cumulative exposed water surface area to 25 square feet, specify a water
recirculation system and make sure all water sprayed into the air from
allowed water features remains within the water feature.
Landscape areas may be watered by hand, manual or automatic irrigation
systems. Permanent irrigation systems are not required. But when hand
watering, make sure your hoses are equipped with an automated, shut off
nozzle and a hose bibb vacuum breaker.
Last updated: Wednesday, 04/04/2012