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A 20-micron sediment filter catches smaller particles than a 50-micron filter. That means it can produce clearer water, but it also creates more flow resistance and may clog faster.
For many rainwater systems, the two filters are not competitors. They can work well together. A 50-micron filter can remove larger debris first, followed by a 20-micron filter for finer sediment.
What Does Micron Mean?
A micron is a very small unit of measurement. One micron equals one-thousandth of a millimeter.
The micron rating of a sediment filter tells you roughly what size particles the filter is designed to catch.
For example:
- A 50-micron filter targets larger sediment.
- A 20-micron filter targets smaller sediment.
- A 5-micron filter removes even finer particles.
A lower micron number means finer filtration.
The micron rating does not tell you whether the water is safe to drink. Sediment filters mainly remove suspended particles. They do not provide complete protection from bacteria, viruses, dissolved chemicals, or other contaminants.
20 Micron vs. 50 Micron Sediment Filters
| Feature | 20-Micron Filter | 50-Micron Filter |
|---|---|---|
| Particle removal | Finer | Coarser |
| Flow restriction | Usually higher | Usually lower |
| Clogging rate | Usually faster | Usually slower |
| Best position | After coarse filtration | Early in the filter system |
| Typical use | Finer sediment cleanup | Larger dirt, grit, and debris |
| Maintenance | More frequent in dirty water | Usually less frequent |
The exact performance depends on the filter design, size, surface area, and manufacturer's rating system.
What Does a 50-Micron Filter Remove?
A 50-micron sediment filter is usually used as a coarse filter.
It can help remove larger suspended material such as:
- Sand
- Grit
- Rust flakes
- Small pieces of organic debris
- Larger particles washed from a roof or tank
A 50-micron filter is useful when water contains a noticeable amount of sediment. Its larger openings allow water to pass more easily than through a finer filter.
This makes it a good first filter after a rainwater tank, especially when the system also includes finer filtration downstream.
Some 50-micron filters are washable screens or spin-down filters. These can be convenient where the water carries a lot of coarse material because the trapped sediment can often be flushed or cleaned instead of replacing the entire filter.
What Does a 20-Micron Filter Remove?
A 20-micron sediment filter removes smaller suspended particles than a 50-micron filter.
It may catch:
- Fine sand
- Smaller rust particles
- Fine dirt
- Sediment that passes through a coarse screen
- Some suspended material that makes water look cloudy
It is often used as a second filtration stage.
For example, rainwater might move through this sequence:
Roof and gutter screening → tank → 50-micron filter → 20-micron filter → additional treatment if needed
The 50-micron stage catches larger material before it reaches the 20-micron filter. This can help the finer filter last longer.
Which Filter Gives Better Water Flow?
A 50-micron filter will usually allow better flow than a similar 20-micron filter.
Water must pass through smaller openings in a finer filter. Those openings create more resistance.
The difference may be small when the filter is clean, especially if the filter housing and cartridge are large enough for the required flow. But the difference often becomes more noticeable as sediment builds up.
A clogged 20-micron cartridge can cause:
- Lower faucet pressure
- Weak irrigation flow
- Longer pump run times
- Pressure drops when several fixtures operate
- Reduced sprinkler performance
Filter size matters too. A large 20-micron cartridge may provide better flow than a small 50-micron cartridge because it has more filtering surface area.
Do not choose a filter using micron rating alone. Check the required flow rate and the pressure limits of the whole system.
Which Filter Clogs Faster?
A 20-micron filter normally clogs faster because it catches smaller particles.
Imagine sweeping gravel through two screens. A screen with large holes lets most of the small material pass. A screen with smaller holes catches much more of it.
The same basic idea applies to sediment filters.
If dirty tank water is sent directly through a fine cartridge, the filter may load with sediment quickly.
You can often reduce this problem by using several forms of debris control before the fine filter, such as:
- Gutter guards where appropriate
- Downspout screens
- A first-flush device
- Tank inlet screening
- Allowing sediment to settle in the tank
- A coarse prefilter
A first-flush device diverts some of the first roof runoff from a rain event. This first runoff can contain more dust, pollen, droppings, and loose debris from the roof.
Is a 20-Micron Filter Better Than a 50-Micron Filter?
Not always.
A 20-micron filter provides finer filtration, but finer does not automatically mean better for every system.
A 50-micron filter may be the better choice when:
- You need high water flow.
- The water contains a lot of coarse sediment.
- You are protecting pumps or larger irrigation components.
- The filter is being used as the first stage.
- You want a washable prefilter before cartridge filtration.
A 20-micron filter may be more useful when:
- Water has already passed through coarse filtration.
- Fine sediment is still reaching faucets or equipment.
- You want an intermediate stage before a finer filter.
- Sediment is affecting valves, emitters, or other equipment.
Many systems work better with staged filtration than with one very fine filter.
Can You Use a 50-Micron Filter Before a 20-Micron Filter?
Yes. In many systems, this is the better arrangement.
Install filters from coarse to fine:
50 micron → 20 micron
Alongside key facts about a better water filter, 5 micron or 20 micron, compare what the measured values reveal and what remains uncertain.
The first filter removes the larger sediment. The second catches smaller particles.
This setup can reduce the amount of material reaching the finer cartridge and may extend its service life.
Adding even finer filtration after that can sometimes make sense, but only when the intended water use requires it.
Installing several fine filters without a reason can increase cost, maintenance, and pressure loss.
Which Is Better for Rainwater Harvesting?
For rainwater harvesting, the right micron rating depends on what you plan to do with the water.
Garden irrigation
A 50-micron filter may be enough for some basic hose or irrigation systems, especially if the water already passes through good inlet screening.
Drip irrigation can require finer filtration because small passages in emitters can clog. Follow the irrigation equipment manufacturer's filtration requirements rather than choosing a micron rating by guesswork.
Pumps and pressure systems
A coarse sediment filter can help keep larger debris away from pumps, valves, and pressure-system components.
However, filters should be placed where the pump can operate correctly. Putting a restrictive filter on the suction side of a pump can cause problems in some installations.
Follow the pump manufacturer's instructions for filter location and allowable suction restriction.
Toilets and laundry
Indoor non-potable rainwater systems often need finer and more carefully controlled filtration than simple garden systems.
Non-potable means the water is not intended for drinking.
These systems may also be subject to plumbing, cross-connection, labeling, and treatment rules. Check current local requirements before connecting harvested rainwater to household plumbing.
Drinking water
Neither a 20-micron nor a 50-micron sediment filter makes rainwater safe to drink.
A sediment filter is only one possible part of a larger treatment system.
Potable rainwater treatment may involve suitable collection surfaces, debris control, prefiltration, finer filtration, disinfection, system maintenance, and current laboratory testing. Potable means suitable for drinking.
Water quality can change with the roof, storage tank, weather, wildlife activity, plumbing, and maintenance. Follow current public-health guidance and local requirements if harvested rainwater will be used for drinking.
Should You Start With 20 Microns or 50 Microns?
Start with the largest particle size you actually need to remove.
If the water contains visible grit or tank sediment, beginning with 50 microns usually makes more sense than sending everything directly into a 20-micron cartridge.
You can then add finer stages if the intended use requires them.
A practical setup might look like:
- Roof and gutter debris screening
- Tank inlet screening
- 50-micron coarse sediment filter
- 20-micron sediment filter
- Any additional treatment required for the intended use
Not every system needs every stage.
The best filter arrangement balances water quality with flow, pressure, maintenance, and the equipment that needs protection.
Watch the Pressure Drop
Any sediment filter creates some resistance to water flow.
As the filter fills with dirt, that resistance increases.
A noticeable pressure drop often means the cartridge or screen needs cleaning or replacement.
Do not simply install a finer filter when flow becomes poor. A clogged cartridge, undersized housing, dirty screen, weak pump, or restricted pipe can cause the same problem.
Pressure gauges installed before and after a filter can make it easier to see when the filter is becoming restricted.
Frequently Asked Questions
Is 20 microns finer than 50 microns?
Yes. A 20-micron filter catches smaller particles than a 50-micron filter. Lower micron numbers mean finer filtration.
Can I use a 20-micron filter by itself?
You can, but it may clog quickly if the water contains a lot of coarse sediment. Using a coarser filter first can reduce the amount of debris reaching the 20-micron cartridge.
Should a 20-micron filter go before or after a 50-micron filter?
The 50-micron filter should normally go first. Filters are usually arranged from coarse to fine, so the 20-micron filter goes downstream.
Will a 20-micron filter remove bacteria?
Do not rely on a sediment filter to control bacteria. A 20-micron filter is intended mainly for suspended sediment and is not a complete drinking-water treatment method.
Is a 50-micron filter good for rainwater?
It can be a useful coarse filtration stage for rainwater, especially for removing larger sediment before finer filters or equipment. The right rating depends on how the water will be used.
Will a 20-micron filter reduce water pressure?
It can. A finer filter usually creates more resistance than a coarser one, and the pressure loss increases as the filter becomes dirty. Housing size, flow rate, cartridge design, and pipe size also affect pressure.
Do I need both 20- and 50-micron filters?
Not always. Using both can be helpful when the source water carries a mix of coarse and fine sediment. Simple irrigation systems may need only coarse filtration, while other uses may benefit from staged filtration.
