Choosing Sediment Filters & Micron Ratings Correctly
The sediment filter is the first and often most important stage of any water treatment. It retains rust, sand, sludge, suspended matter and the finest particles before the water reaches sensitive fittings, heat exchangers or downstream treatment stages. Decisive for its effect is the correct micron rating: if it is chosen too coarse, particles pass through the filter unhindered; if it is chosen too fine, the pressure loss rises and the filter clogs prematurely. This guide shows installers and technically minded end customers how to select the appropriate sediment filter and micron rating for domestic water, drinking water and heating applications.
What the micron rating of a sediment filter means
The micron rating (or micrometre rating) indicates the particle size from which a filter retains. One micron equals one thousandth of a millimetre. The smaller the number, the finer the filtration: a 1-micron filter retains significantly smaller particles than a 20-micron filter. For orientation – a human hair is around 50 to 70 microns thick, fine sand is at about 100 microns, and particles below 35 microns are no longer visible to the naked eye.
Nominal rating vs. absolute rating
When evaluating, a distinction must be made between two specifications. The nominal rating describes that a high proportion of particles from the specified size is retained – a typical guideline value in domestic water treatment. The absolute rating, on the other hand, guarantees almost complete retention from the specified size and is used above all in particularly critical applications. For classic pre- and sediment filtration in a building, nominal ratings are usually used.
Which micron rating for which application?
Staged filter chains are the rule in practice: a coarser filter catches the main load, a finer one protects downstream stages. As a guide for typical use cases:
- 20 microns: coarse pre-filtration for heavily particle-laden water, for example from wells or older pipe networks. Protects the subsequent fine stage from overload.
- 10 microns: universal all-rounder for central domestic water filtration. A good compromise of retention capacity, dirt holding and service life.
- 5 microns: fine filtration for drinking water at the point of use as well as a pre-filter upstream of activated carbon or reverse osmosis stages, since fine particles spare the downstream media.
- 1 micron: very fine filtration upstream of sensitive stages such as reverse osmosis membranes or where there are particularly high requirements for freedom from particles.
The grooved PP sediment filters from GWS are made of 100% pure, chemical-free polypropylene and are available in the nominal ratings of 1, 5, 10 and 20 microns. Their dual-gradient structure offers up to 80% more surface area than a standard sediment filter, which significantly increases the dirt holding capacity and extends the service life.
Keeping pressure loss, flow rate and service life in view
Every sediment filter generates a pressure loss that increases as fouling progresses. A finer micron rating tends to mean a higher initial pressure loss and faster clogging at the same flow rate. Anyone who chooses the fineness without regard to flow rate risks falling water pressure and frequent filter changes.
Two levers compensate for this: a larger filter format and staged filtration. A larger housing with a larger cartridge offers more filter area, keeps the flow rate stable for longer and extends the replacement intervals. The grooved PP sediment filters are available both in the standard design (2.5″) and in the jumbo format (4.5″) – the jumbo format is suitable for higher flow rates and central supply at the building entrance. As a practical guideline for filter replacement, the manufacturer-recommended pressure loss of around 1.5 bar applies; a differential pressure gauge on the housing makes this point visible.
Selecting the right filter housing
The best filter element only works as well as the housing it sits in. Several points must be considered when selecting the housing:
- Size: 10″ or 20″ in standard or jumbo design – matched to the required flow rate and the available space.
- Connection size: from 1/4″ via 1/2″ and 3/4″ up to 1″, matching the existing pipework so that the connection does not become a bottleneck.
- Material and pressure: robust polypropylene housings for high pressures or transparent housings for visual inspection of the degree of fouling.
- Pressure relief valve (PRV): facilitates filter replacement, as the residual pressure can be released before opening.
In the range of Filter Housings you will find suitable standard and jumbo housings in various connection variants, with or without a pressure relief valve. It is important that the housing size and cartridge size match each other – a 10″ element belongs in a 10″ housing, a 20″ element in a 20″ housing.
Practical selection checklist
Before sizing, these points help to determine the right sediment filter:
- Check the water source: mains water, well or spring? Well and spring water usually carry more sediment and need a coarser pre-stage.
- Define the goal: protection of the entire domestic water network (point-of-entry) or fine filtration at the drinking water tap (point-of-use)?
- Stage the micron rating: with a high particle load, first coarse (e.g. 20 or 10 microns), then fine (5 or 1 micron) – this extends the service life of the fine stage.
- Secure the flow rate: choose the filter format and connection size so that the required flow rate is achieved without a strong pressure drop; when in doubt, choose the jumbo format.
- Pre-stage upstream of sensitive media: always protect activated carbon and reverse osmosis membranes with a sediment pre-filter to extend their service life.
- Plan maintenance: monitor the differential pressure and replace the element in good time – not only when the water pressure noticeably drops.
A correctly selected sediment filter is the inexpensive insurance for the entire downstream system. Anyone who matches the micron rating, filter format and housing to one another obtains clean water at stable pressure and with long replacement intervals – the basis for any reliable domestic and drinking water treatment.
Sediment filters and micron ratings compared: PP sediment, GAC and filter housings
Which filter type and which micron rating suits your water? The following overview compares grooved and wound PP sediment filters, granular activated carbon (GAC), carbon blocks and combination cartridges by micron rating, material, function and typical application – so you can correctly combine sediment filters and filter housings.
| Filter type | Micron rating (nominal) | Material & construction | Function & typical application |
|---|---|---|---|
| Grooved PP sediment filter | 1, 5, 10 and 20 micron | Polypropylene, dual-graded grooved structure with large surface area | Mechanical separation of sand, rust and particles; high dirt-holding capacity and long service life as a pre-filter or standalone sediment stage |
| Wound PP sediment filter | typically 5-50 micron | Polypropylene, string-wound with depth filtration effect | Depth filtration for coarse to medium sediment; proven, economical pre-filter for water with higher particle loads |
| Granular activated carbon (GAC) | 1 micron (integrated BLOCKFREE PP filter) | 100% coconut-shell granulate in cartridge | Reduces chlorine, odour and taste; pre- or post-stage in RO and drinking-water systems, not for fine particle filtration |
| Carbon block | 5 micron | Pressed carbon block made from coconut-shell carbon | Combines fine-particle and chlorine/taste filtration; ideal as a final stage before the tap (point-of-use, RO, coffee) |
| Dual-media cartridge (combination filter) | PP grooved pre-filter: 5 micron | Grooved PP pre-filter plus activated carbon in one cartridge | Two stages combined to save space: first sediment, then taste/odour – saves housing space in undersink and POU applications |
| Filter housing (10″ / 20″, standard & jumbo) | depends on the cartridge used | Reinforced polypropylene or clear AS; up to 8.6 bar | Holds the sediment or carbon cartridge at the house or appliance connection; basis for single- or multi-stage filter chains |
Matching products
- Grooved PP Sediment Filters
- Media Cartridges – Granular Activated Carbon (GAC)
- Dual Media Cartridges
- Activated Carbon Blocks
- Standard & Jumbo Filter Housings
- Inline Filters T33 & K33 Series
Frequently Asked Questions
What micron rating should a sediment filter for the whole house have?
For central domestic water filtration at the building entrance, a sediment filter with 10 microns is a proven all-rounder, as it offers a good compromise of particle retention, dirt holding and service life. With heavily sediment-laden water – for example from wells – a coarser pre-stage with 20 microns is recommended, followed by a finer stage.
What does the micron specification on a sediment filter mean?
The micron rating indicates the particle size from which the filter retains. One micron is one thousandth of a millimetre. The smaller the number, the finer the filtration: a 1-micron filter retains significantly smaller particles than a 20-micron filter. For comparison, a human hair is around 50 to 70 microns thick.
Why not simply always choose the finest sediment filter?
A very fine filter (e.g. 1 micron) generates a higher pressure loss at the same flow rate and clogs faster. This can lower the water pressure and leads to more frequent filter changes. A staged filtration is more sensible: first coarse, then fine. This keeps the pressure stable and the fine stage lasts longer.
When does a sediment filter need to be changed?
The filter element should be changed when the pressure loss rises significantly – a practical guideline is around 1.5 bar differential pressure. A differential pressure gauge or a transparent housing makes the degree of fouling visible. You should not wait until the water pressure noticeably drops.
Do I need a sediment filter upstream of a reverse osmosis system?
Yes. A sediment pre-filter protects the sensitive reverse osmosis membrane as well as upstream activated carbon stages from particles and significantly extends their service life. A fine sediment filter with 5 or 1 micron is common here as a pre-stage.