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Parts of an Underground Cistern for Automated Irrigation

A) Rainhead screen: 1/8” screen mesh catches leaves and other roof debris, screen slopes at a 45 degree angle so that debris falls away.

B) First flush diverter: Wall-mounted pipe sized to catch the dirtiest water- the first 1% of roof runoff at the start of each storm.

C) First flush end cap: Pipe ends at elbow with threaded cleanout cap and an irrigation tube run to vegetation nearby to slowly empty first flush pipe after storms.

D) Inflow pipe: Rainfall enters once first flush diverter is filled. Typical pipe is painted plastic and sized based on expected rainwater flow calculated from roof area.

E) Observation port and imbedded vent: Threaded 16” diameter cap, usually closed, provides easy visual access to your stored rainwater. Vent ensures airflow and prevents vacuum effect in heavy rain.

F) Concrete tank: 6” thick, 4000 psi shotcrete shell, sealed with potable-certified concrete sealant for water containment.

G) Overflow pipe: ABS pipe directs water away when the tank is full during a storm.

H) Backwater valve: On the end of the overflow pipe, this one-way flap valve ensures that water can exit but nothing can enter the tank.

I) Mulched basin (optional): Overflow should be used as a resource, and directed to an area with the capacity to accept predicted cistern overflow.

J) Water line from cistern to pump.

K) Pressure-activated pump.

L) Wiring in conduit to power pump.

M) Electric panel.

N) Main irrigation valve, controlled by standard irrigation clock.

O) Irrigation control clock.

P) Cistern water line from pump to irrigation main.

Q) Municipal water line.

R) Municipal water backup float valve, keeps cistern filled with water at 1’ depth when rainwater is low.