Dripline: how long can a run be, pressure-compensating or not

Background

On Italian forums the question comes back every year: can 100, 130 or 160 metres of dripline be fed from a single connection, or does the water only come out of the first emitters [62][63][64]? The answers are usually rules of thumb. Yet some manufacturers publish a table with the maximum run length for each inlet pressure.

How to use it

1. Enter the pressure at the start of the dripline. If the kit has a pressure reducer, it is the reducer’s pressure.
2. If you like, enter the length you want to lay: you see straight away which driplines can handle it.

What the tables say

At 1.5 bar the declared maximum lengths for 16 mm driplines with emitters every 33 cm are:

• Irritec Multibar C (2.1 l/h): about 77 m [60];
• Rain Bird XFS-CV (2.3 l/h): about 87 m [51];
• Rain Bird PCD (2.3 l/h): about 97 m [52];
• Soaplast Uniflow Pc (2.2 l/h): about 98 m [61].

At 2 bar this rises to about 92–117 m. The differences do not tell you which dripline is better: each manufacturer uses its own criterion, and only Soaplast states it (85% emission uniformity). None of the tables gives a slope: they apply to level ground.

Pressure-compensating or not

• Pressure-compensating: the emitter gives almost the same flow at different pressures. Irritec declares 2.05–2.12 l/h from 0.5 to 4 bar [60].
• Non-compensating: the flow follows the pressure. The Claber 90357 pipe gives 1.8 l/h at 0.5 bar and 3.1 l/h at 2 bar, 72% more [58]. Pressure drops along the line, so the first emitters give more water than the last ones. Claber does not publish a maximum length.

How much water the line needs

With a pressure-compensating dripline, the total flow is the number of emitters times the flow of each one. 60 m with an emitter every 33 cm is 181 emitters: at 2.3 l/h that makes about 416 l/h, or about 7 l/min. Your tap or pump has to supply this at the pressure you entered: you can check it with the pump calculator.

Gravity-fed from a tank

Each metre of height between the water level and the dripline is worth about 0.1 bar. A tank raised by 1.5 m gives about 0.15 bar. In the manufacturers’ documents we have read, nobody publishes data below 0.5 bar. At these pressures the behaviour of driplines is not documented, not even that of pressure-compensating ones.

How we read the data: where our data comes from.