The flow demand of a drip zone is the sum of its operating emitters, not the length of the hose or the total number of plants in the garden. Different line groups may also use different emitter ratings.
The Drip Zone Flow Calculator provides a row for each group. Enter its name, emitter count and individual flow in litres per hour. Add the measured supply flow at the relevant operating pressure to see how much flow remains above or below the combined demand.
Two line groups in one zone
A raised bed group with 60 emitters at 2 L/hour needs 120 L/hour. A pot group with 20 emitters at the same flow needs 40 L/hour. Together they require 160 L/hour, or approximately 2.667 litres per minute.
If the entered available supply is 500 L/hour, headroom is 340 L/hour. Change that supply to 100 L/hour and the result becomes negative 60 L/hour. The calculator then states that zone demand exceeds the supplied flow value.
That negative result should not be read as a prediction of the exact flow every emitter will receive. It is a comparison of required and available flow figures under the inputs, not a hydraulic simulation of a starved network.
Give every row the same operating meaning
The rows listed are assumed to run together. If beds and pots operate at different times, calculate their zones separately rather than adding both demands into one simultaneous total.
An emitter count means the outlets in that group, not metres of pipe. For a dripline specified by spacing, establish the actual outlet count before entering it. End details and the number of lines can make a simple pipe length estimate inaccurate.
The supply input should describe what is available at the operating condition. An unrestricted bucket test or a pump's headline flow figure may not represent flow while the system maintains the necessary pressure. The calculator does not make that correction for you.
A useful check before choosing runtime
This worksheet does not size pipes, calculate friction loss, choose a pump or certify emitter uniformity. A positive headroom result covers only the supplied flow comparison. Pressure and distribution still need their own verification.
For the duration needed to deliver a chosen session volume, use Drip Irrigation Runtime Calculator. Keep its simultaneous emitter count consistent with the zone used here. If a mixed zone is represented by an average emitter flow, that average must preserve the total demand rather than merely averaging two ratings without their counts.
Record line names that will make sense later. A row called east beds is easier to review after a layout change than several unnamed lines whose original outlet counts have been forgotten.