Drip Zone Planning Sheet

The arithmetic

Supply in gpm

bucket gallons ÷ seconds x 60

Supply in gph

bucket gallons ÷ seconds x 3600

Usable supply

gph x (1 − margin)

Emitters per zone

usable gph ÷ emitter gph

Zones

emitters wanted ÷ per zone, ROUNDED UP

Demand at once

emitters x their rated flow

Water per cycle

demand x run hours

⚠ Tubing length limit

from the manufacturer — separate

This system

Date

Tap

Bucket size

Seconds to fill

SUPPLY gpm

SUPPLY gph

Emitter rating

Margin

EMITTERS PER ZONE

Emitters wanted

ZONES NEEDED

Run time

WATER PER CYCLE

Zones

Before and after assembly

• Tap measured with a bucket, not estimated
• Nothing else running in the house during the test
• Emitter rating read off the part, not assumed
• Margin chosen deliberately, not left at zero by accident
• Tubing run length checked against the manufacturer's limit
• Filter fitted at the head of the system
• Pressure regulator fitted - mains is too high for drip fittings
• Pressure-compensating emitters considered for slopes and long runs
• System flushed before the emitters go on
• Far end checked while running - that is where trouble shows first

The far end tells you first

When a zone is over its limit, plants nearest the tap look fine and the ones at the end stay dry. It reads like a blocked emitter or a thirsty plant, and it is neither - there is not enough flow left to hold pressure along the run. Check the far end while the system is running before blaming anything else.

Flow is only half the problem

Every tubing diameter has a maximum run length, published by its manufacturer and varying with emitter spacing. A zone can pass the flow arithmetic on this sheet and still underperform because the line is simply too long. Check both numbers before buying, because the fix afterwards is a second zone.