choice of feed outlet is crucial for making sure all roots are adequately
fed. The decision will depend upon factors such as system type, system
volume and flow rate requirements.
1. Bare hose end:
Blockages are least likely. This is the preferable method for NFT or any
system where the outlet flow does not need to be sprayed or tightly
regulated. If needed, the flow rate is adjustable via an in-line tap.
2. Flood & Drain: Specific to ‘Flood
& Drain’ systems.
Drippers: These are typically used for
- “Pressure compensating” drippers
deliver a preset flow rate (Fig 2.4). These are ideal for run-to-waste
systems for obtaining a specific percentage run-off (see
- “Adjustable” drippers permit the flow
rate to be adjusted. However, because these are ‘non’ pressure
compensating, their output will vary with delivery pressure.
- Drippers are prone to blocking
therefore make sure they can be dismantled for routine cleaning (Fig
4. Sprayers / Jets: (Fig 2.5) Use
these when top-feeding to achieve an even distribution of nutrient over
the surface of pots (Fig 1.6).
However, note that they are prone to blockage, and will increase
evaporation losses and salt build-up.
Equilibrating feed outlet flow
In run-to-waste systems it is often necessary
to obtain the same flow rate from each feed outlet. This can be achieved
by using “pressure compensating” drippers. These will yield a preset flow
rate (Fig 2.4). They are however, not always desirable because they are
susceptible to blockages.
If “pressure compensating” drippers are not
feasible, feed outlet flow rates can be equilibrated as follows:
1. Use maximum diameter piping for the
2. Pipes joining the primary circuit to the
feed outlets must be of equal length and diameter. Note that using wider
pipes will reduce the need for being consistent with this requirement.
3. Feed outlets must be of equal type and
specification. Ensure the outlets are maintained to avoid partial
blockages. Partial blockages will distort outlet flow rates.