Without a filter, drippers and nozzles clog faster than you can replace them. Even fine sand, silt or algae particles block the narrow water paths and lead to uneven irrigation. A suitable filter for irrigation is therefore essential – for hobby gardeners with a dripline just as much as for farmers and landscapers with large drip systems. This guide shows which filter type suits which situation.
Why a filter is indispensable in irrigation
Drippers and micro-sprayers work with very narrow passages, often in the range of just a few tenths of a millimetre. It is precisely these bottlenecks that ensure the exact, economical water release – but they are also the weak point. Particles from well, cistern or pond water, as well as lime and algae flakes, build up and gradually clog the outlets.
The consequences are costly: individual plants get too little water, the pressure in the system rises, and in the worst case whole driplines have to be replaced. A filter holds back the critical particles before they enter the system. It is therefore the cheapest insurance against failures – and a prerequisite for manufacturer warranties on drip systems to apply at all.
Sieve filter vs. disc filter
In practice, two designs compete: the sieve filter and the disc filter. Both remove solids, but they work differently.
Sieve filter – how it works
The sieve filter (also mesh filter) filters the water through a cylindrical screen made of plastic or stainless steel. Particles are held back on the surface of the screen. This makes it cheap, robust and very easy to clean – the screen is simply removed and rinsed off. With heavily organically loaded water (algae, slime), however, the smooth screen surface clogs more quickly.
Disc filter – how it works
In a disc filter, many thin, grooved ring discs are stacked on top of each other and pressed together. The water flows through the fine channels between the discs. This creates a three-dimensional depth filtration that can take up considerably more dirt before the flow rate drops. This is particularly advantageous with organic loads. To clean it, the discs are released and rinsed.
| Criterion | Sieve filter | Disc filter |
|---|---|---|
| Filter principle | Surface filtration | Depth filtration (stacked discs) |
| Dirt uptake | low to medium | high |
| With algae/organics | clogs more quickly | very well suited |
| Cleaning | very easy (rinse screen) | easy (rinse discs) |
| Purchase cost | low | slightly higher |
| Ideal for | clear water, mains/cistern water | well, pond, surface water |
Recommendation: For clean water and smaller systems, a sieve filter is sufficient. For organically loaded or fluctuating water as well as larger drip systems, the disc filter is the more reliable choice.
Mesh size: understanding Mesh, micron & µm
The fineness of a filter is given in Mesh or in micrometres (µm, colloquially micron). Mesh denotes the number of meshes per inch (25.4 mm): the higher the Mesh number, the finer the filter and the smaller the mesh opening in µm. A high Mesh number therefore means smaller micron values – the two scales run in opposite directions.
| Mesh | Mesh opening (µm, approx.) | Typical application |
|---|---|---|
| 40 Mesh | ~400 µm | pre-filter, coarse sprinklers |
| 80 Mesh | ~180 µm | sprinklers, robust micro-sprayers |
| 120 Mesh | ~130 µm | standard for drip irrigation |
| 150 Mesh | ~105 µm | fine drippers, pressure-compensating |
| 200 Mesh | ~75 µm | very fine drippers, misting |
As a rule of thumb: the filter fineness should be about one tenth of the smallest passage in the dripper. For most drip systems, 120 Mesh (~130 µm) is the proven standard. Sprinklers and coarser micro-sprayers manage with 80 Mesh, while very fine drippers and misting nozzles require 150 to 200 Mesh. If in doubt, the dripper manufacturer’s specification gives the exact recommendation.
Choosing the filter size according to flow rate
Besides fineness, the flow rate determines the right filter size. If the filter is too small, pressure loss rises and the filter clogs faster. The connection size should match the line and the required amount of water.
| Connection | Guide value flow rate | Field of use |
|---|---|---|
| 3/4″ | up to approx. 3 m³/h | home garden, small drip system |
| 1″ | approx. 3–6 m³/h | large garden, several circuits |
| 1 1/2″ | approx. 6–15 m³/h | agriculture, landscaping |
| 2″ | from approx. 15 m³/h | large irrigation areas |
Important: the flow rate values are guide values. The manufacturer’s filter specifications, the permissible pressure loss and the actual demand of your system are always decisive.
Common mistakes & maintenance
- Filter chosen too fine: a filter that is too fine clogs constantly and throttles the flow rate unnecessarily. Match the fineness to the dripper type.
- Filter undersized: too small a connection increases pressure loss. Better to choose one size larger.
- Forgetting to clean: check the filter regularly and rinse it before each season and after any turbidity.
- Wrong installation direction: observe the flow direction (arrow on the housing), otherwise the filter does not work correctly.
- Frost protection: drain the filter and housing before winter to avoid frost damage.
FAQ
Which mesh size do I need for drippers?
For most drip systems, 120 Mesh (about 130 µm) is the proven standard. Very fine, pressure-compensating drippers and misting nozzles require finer filters with 150 to 200 Mesh. If in doubt, the dripper manufacturer’s filter recommendation always applies.
Which is better: sieve or disc filter?
For clear water and small systems, a low-cost sieve filter is enough. For organically loaded water from a well, pond or cistern, the disc filter is the more robust choice thanks to its depth filtration, because it takes up more dirt before the flow rate drops.
How often do I have to clean the filter?
That depends on the water quality. With clean water, a check every few weeks is enough; with turbid well or pond water, the filter should be rinsed weekly or after each longer run. A noticeable pressure drop is always a sign to clean it.
Does a higher Mesh number mean a finer filter?
Yes. Mesh indicates the meshes per inch. The higher the Mesh number, the smaller the individual mesh opening in micrometres. 120 Mesh therefore corresponds to a finer filter (~130 µm) than 80 Mesh (~180 µm).
The right filter is the foundation of trouble-free irrigation. A suitable selection of robust Poelsan plastic filters can be found in our catalogue, as well as the matching drip accessories for a secure connection. If you are planning a complete system, you will find further steps in the guide hub Planning your irrigation. For the detailed design, it is worth taking a look at our range of plastic filters – matched to the flow rate and fineness of your system.
Expert advice from KLN: are you unsure when choosing the filter type, mesh size or connection size? As a distribution partner for Poelsan products, KLN & Heumann GmbH advises you professionally and manufacturer-independently on your irrigation system.