Drip System Flow & Size Your Pump & Mainline

It's simply the number of emitters running at once multiplied by each emitter's rated discharge. For example 2,000 emitters at 4 L/h each gives 8,000 L/h = 8 m³/h ≈ 2.22 L/s. That single number is the demand your pump, filter and pipes must supply, so it's the starting point for the whole design.

Every component is sized from it: the pump must deliver this flow at the required pressure, the filter must be rated for at least this flow, and the mainline and submains must carry it without excessive friction loss. Get the flow right and the rest of the design follows; guess it and you under- or over-size expensive hardware.

Then you can't run the whole field at once. Your source — a borewell, canal turn, tank or pump — has a maximum it can deliver. If total emitter flow is higher, you split the field into zones and irrigate one zone at a time, so each zone's flow stays within what the source and pump can supply.

Dividing the field into zones (operated by separate valves) means only one zone's emitters draw water at a time. Each zone is sized so its flow ≤ the pump's and source's capacity. You then schedule the zones in sequence. The tool's total flow tells you how many zones you need and how big each can be.

It reports system flow in litres per hour (L/h), cubic metres per hour (m³/h) and litres per second (L/s), plus the total emitter count. L/h is handy for matching emitter ratings, m³/h for pump and tank sizing, and L/s for friction-loss and pipe-diameter checks. Use whichever your other tools and datasheets expect.

It's printed on the dripline or emitter spec — common ratings are 1, 2, 4 or 8 L/h at the design pressure. Pressure-compensating (PC) emitters hold that rate over a range of pressures; non-PC emitters vary with pressure, so use the rating at your operating pressure for an accurate total.

Divide your pump's deliverable flow by each emitter's discharge. A pump giving 10 m³/h (10,000 L/h) can run about 2,500 emitters at 4 L/h. If your field has more, split it into zones so no single zone exceeds that emitter count. The tool makes this division easy to check.

Friction loss doesn't change the emitters' total demand, but it does raise the pressure the pump must produce to deliver that flow. Size the mainline so friction loss is modest at the system flow, and pick a pump rated for the flow at the resulting total head. The Lateral Length and Pump Power tools help here.

The total flow is exact for the emitter count and discharge you enter. Real systems vary slightly with pressure, emitter clogging and manufacturing tolerance, so add a margin when sizing the pump and filter, and recheck flow if you change emitter spacing, dripline or the number of zones running together.