Flow Rate Test

BUCKET METHOD // v2.1

Knowing your irrigation system's flow rate is essential before selecting sprinklers, sizing pipes, or programming run times. The bucket test is the most reliable DIY method — all you need is a bucket and this page.

01 — Select Bucket Size
02 — Stopwatch
00:00
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READY
03 — Flow Rate Results
Output mode:
Litres / Minute —L/min
Litres / Hour —L/hr
— imperial —
Gallons / Minute —Imp gal/min
Gallons / Hour —Imp gal/hr
— test info —
Time Elapsed —sec
Bucket Volume —L
Stop the timer to see flow rate results
◈ Formula Used
Flow rate (L/min) = [Volume (L)] ÷ [Time (sec)] × 60 × 0.8
The × 60 converts seconds to minutes. In ×0.8 irrigation mode a 20% reduction is applied to account for pressure drop across your system — the tap is typically at higher pressure than the irrigation zone. If you tested directly at operating pressure, or just want the raw tap flow, switch to full flow mode above. Imperial gallons are used (1 Imp gal = 4.54609 L).
01 Pick your time of day — water pressure fluctuates throughout the day. Run the test at the same time you plan to irrigate so the result reflects real-world conditions.
02 Turn off everything else — make sure no taps, toilets, or other zones are running on the property. Any parallel draw will skew the result.
03 Turn the tap on fully first — let the water run freely before placing the bucket underneath. You want to capture mid-stream flow, not the initial surge.
04 Slide the bucket in and hit Start — time how long it takes to fill to your chosen volume. Stop the timer the moment it reaches that mark.
05 Read your result above — L/min is the most useful figure for irrigation planning. Use it to calculate zone run times or check how many sprinkler heads your system can support simultaneously.
TIP — For a more accurate reading, run the test two or three times and average the results. Variations of more than 10% between runs may indicate pressure inconsistency at the meter.
05 — Frequently Asked Questions
How do I measure my tap's flow rate?

Use the bucket test on this page. Pick a bucket of known volume, turn the tap on fully, start the stopwatch as the bucket slides under the stream, and stop it the moment the bucket reaches its mark. The calculator divides volume by fill time to give your flow rate in litres per minute, plus L/hr and imperial gallons.

What is a good flow rate for home irrigation?

Most Perth homes on mains water measure roughly 15–25 L/min at an outside tap, but it varies with your meter size, plumbing and the time of day. There's no single "good" number — what matters is choosing sprinklers and zone sizes that fit the flow rate you actually measured.

Why does the calculator multiply by 0.8?

In ×0.8 irrigation mode the result is reduced by 20% to allow for pressure drop between the tap and the irrigation zone — valves, pipe runs and fittings all cost you some flow. If you tested at the zone itself, or you just want the raw tap figure, switch the results to full flow mode.

How many sprinklers can I run on one zone?

Add up the flow demand of every head on the zone (from the nozzle manufacturer's chart — pop-up sprays typically draw a few litres per minute each) and keep the total under your measured flow rate. Many installers design to about 80% of measured flow as a safety margin, which is exactly what the ×0.8 mode gives you.

What's the difference between flow rate and pressure?

Flow rate is how much water moves per unit of time (L/min). Pressure is the force pushing it (kPa). Sprinklers need enough pressure to throw water their rated distance and enough flow to feed every head at once — the bucket test measures flow only, so check pressure separately if heads aren't performing.