Screen filters vs Disc filters are designed to remove impurities from water before it reaches the irrigation lines, but they work differently and are suited to different water sources.
Clean water is one of the most important requirements for a successful irrigation system. Whether you are using drip irrigation, rain hose, sprinklers, or micro-sprinklers, dirty water can block pipes, clog emitters, reduce water flow, and lower crop yields.
Without proper filtration, mud, sand, algae, leaves, and other particles can damage the irrigation system and increase maintenance costs.
Why Water Filtration Is Important
Water collected from rivers, dams, boreholes, canals, ponds, and storage tanks often contains impurities such as sand, silt, mud, algae, leaves, insects, organic matter and small stones.
If these particles enter an irrigation system, they can clog emitters and reduce water distribution.
Proper filtration keeps the system working efficiently and extends the lifespan of irrigation equipment.
Common Sources of Irrigation Water
The type of filter you need depends largely on your water source. Each source contains different levels of suspended particles and organic matter.
The Common irrigation water sources typically depend on in Kenya include:
- Boreholes
- Rivers
- Earth dams
- Water pans
- Lakes
- Roof rainwater harvesting tanks
- Municipal water supply
The Role of Filtration in Drip Systems
Drip irrigation delivers water through very small emitters.
These emitters have tiny openings designed to release water slowly and evenly.
Even small particles can block these openings.
Without proper filtration, farmers may experience:
- Uneven irrigation
- Reduced water pressure
- Dry crop sections
- Frequent repairs
- Increased labour costs
Benefits of Irrigation Water Filters
A good filtration system provides several advantages:
- Prevents emitter clogging
- Improves water flow
- Reduces maintenance costs
- Extends equipment lifespan
- Improves irrigation efficiency
- Supports uniform crop growth
- Protects valves and pressure regulators
NB: For farms using fertigation, filters also help maintain a smooth flow of dissolved fertilisers through the system.
Types of Irrigation Water Filters
Several filter types are available for irrigation systems.
The most common include:
| Filter Type | Primary Use |
| Screen Filter | Removes sand and coarse particles |
| Disc Filter | Removes fine particles and organic matter |
| Sand Media Filter | Suitable for dirty surface water |
| Hydro cyclone Filter | Removes heavy sand from borehole water |
Among these, screen filters and disc filters are the most widely used for small and medium-sized farms.
Screen Filters: Specs, Mesh Sizes, and Best Uses
A screen filter uses a stainless steel or plastic mesh to trap particles as water flows through it.
The mesh acts like a sieve, allowing clean water to pass while retaining larger particles.
How Screen Filters Work
Water enters the filter housing and passes through the screen.
Particles larger than the mesh openings remain trapped on the surface of the screen.
The filtered water then flows into the irrigation system.
Common Screen Filter Specifications
Screen filters are available in different sizes, mesh ratings, flow capacities and connection diameters.
The correct size depends on the irrigation system and expected water demand.
Understanding Mesh Sizes
Mesh size refers to the number of openings per inch on the filter screen. Right mesh sizes help protect emitters without unnecessarily restricting water flow. A higher mesh number means smaller openings and finer filtration.
Common mesh ratings include:
| Mesh Size | Typical Application |
| 80 Mesh | Sprinkler irrigation |
| 120 Mesh | Standard drip irrigation |
| 150 Mesh | Fine drip systems |
| 200 Mesh | Very fine filtration |
Advantages of Screen Filters
Screen filters offer several benefits:
- Affordable
- Easy to install
- Simple to clean
- Low maintenance
- Suitable for clean water sources
Best Uses for Screen Filters
Farmers using relatively clean water sources often find screen filters sufficient.
Screen filters are ideal for:
- Borehole water
- Municipal water
- Roof rainwater harvesting systems
- Clean storage tanks
Disc Filters: Specs, Depth Filtration, and Best Uses
Disc filters work differently from screen filters.
Instead of a single mesh screen, they contain many grooved plastic discs stacked tightly together.
When compressed, the grooves create numerous tiny pathways that trap impurities.
How Disc Filters Work
Water flows through the stack of discs.
Particles become trapped between the grooves rather than only on the surface.
This process is known as depth filtration.
Because particles are captured throughout the disc stack, disc filters usually hold more dirt before requiring cleaning.
What Is Depth Filtration?
Contaminants are trapped within several layers instead of only on the outer surface.
This allows disc filters to:
- Handle dirtier water
- Capture finer particles
- Reduce cleaning frequency
Common Disc Filter Specifications
Disc filters are available in various:
- Flow capacities
- Disc grades
- Connection sizes
- Pressure ratings
Advantages of Disc Filters
Disc filters offer many benefits:
- Excellent filtration efficiency
- Longer cleaning intervals
- Better handling of organic matter
- Improved protection for drip systems
- Greater dirt-holding capacity
They are especially suitable for farms using surface water.
Best Uses for Disc Filters
Disc filters are recommended for:
- River water
- Dam water
- Water pans
- Open reservoirs
- Canal water
Screen Filters vs. Disc Filters
| Feature | Screen Filter | Disc Filter |
| Filtration Method | Surface filtration | Depth filtration |
| Best Water Source | Clean water | Dirty surface water |
| Organic Matter Removal | Moderate | Excellent |
| Dirt-Holding Capacity | Moderate | High |
| Cleaning Frequency | More frequent | Less frequent |
| Purchase Cost | Lower | Higher |
| Maintenance Complexity | Simple | Moderate |
Sizing Your Filter: Flow Rate Matching
A filter should be compatible with its piping system. There are factors that contribute to choosing of a filter for specific function, such as:
- Water pressure
- Water flow rate
- Cleaning frequency
What Is Flow Rate?
Flow rate is the volume of water passing through the irrigation system within a certain time.
It depends on:
- Farm size
- Number of emitters
- Sprinklers
- Irrigation schedule
Why Flow Rate Matching Matters
The filter should comfortably handle the system’s maximum flow demand.
Proper sizing ensures:
- Stable pressure
- Uniform irrigation
- Longer filter life
- Reduced maintenance
Factors to Consider When Sizing a Filter
Before selecting a filter, consider:
- Water source quality
- Pump capacity
- Pipe diameter
- Irrigation area
- Future farm expansion
Backwashing and Cleaning.
Backwashing is a cleaning process where water flows in the opposite direction through the filter.
This reverses the normal flow and flushes trapped dirt out of the filter.
Automatic backwashing systems are common on larger irrigation projects because they reduce manual labour and maintain consistent filter performance.
Backwashing and Cleaning Procedures
Regular maintenance keeps irrigation filters working efficiently.
The cleaning method depends on the filter type.
Cleaning Screen Filters
Screen filters are straightforwardly too clean.
1.Turn off the water supply.
2.Release pressure from the filter housing.
3.Remove the screen.
4.Wash with clean water.
5.Use a soft brush if necessary.
6.Reinstall the screen.
NB: Inspect the screen for damage before replacing it.
Cleaning Disc Filters
Disc filters require a slightly different process.
1.Shut off the water supply.
2.Open the filter housing.
3.Remove the disc stack.
4.Separate the discs.
5.Wash thoroughly with clean water.
6.Reassemble the discs correctly.
7.Reinstall the filter.
NB: Ensure no dirt remains trapped between the grooves.
How Often Should Filters Be Cleaned?
Farmers using river or dam water may need to inspect filters more often than those using borehole water.
Cleaning frequency depends on:
- Water quality
- Irrigation hours
- Season
- Filter size
Signs Your Filter Needs Cleaning
- Reduced water pressure
- Uneven irrigation
- Slow dripper flow
- Increased pump workload
- Visible dirt inside the filter housing
Cleaning the filter promptly prevents damage to the irrigation system.
Tips for Extending Filter Life
To keep filters working efficiently:
- Inspect them regularly.
- Clean them before they become heavily blocked.
- Protect them from physical damage.
- Replace worn seals and damaged screens or discs.
- Install the filter in an accessible location for easy maintenance.