Cartridge Filter Size Guide: 5 Micron, 10 Micron, 10-Inch & 20-Inch Filters Explained (2026)

By Pearl Water Technologies | Updated June 2026 | Water Treatment Expert Guide

If you own an RO water purifier, you already depend on a cartridge filter every single day. These small cylindrical filters are the first line of defence for your RO membrane. They trap dust, dirt, rust, sand, and microscopic particles before the water ever reaches the sensitive membrane inside your purifier.

Choosing the right cartridge filter micron size is one of the most important decisions you can make for your water purifier. Get it wrong and you risk clogged membranes, poor water quality, and costly repairs. Get it right and your purifier runs efficiently for years.

In this complete guide, Pearl Water Technologies — a leading supplier of RO spare parts and filtration solutions across India — explains everything you need to know about 5 micron filters, 10 micron filters, 10-inch and 20-inch cartridge sizes, pre-filter cartridges, prices in India, and how to choose the best option for your water source.

What is a Cartridge Filter?

A cartridge filter is a cylindrical filtration element placed inside a filter housing. Water flows through the outer surface of the cartridge and exits through the hollow centre, leaving suspended particles trapped in the filter material.

In an RO water purifier, cartridge filters are installed as pre-filters — they protect the RO membrane by removing sediment before it can clog or damage the membrane. Without them, the membrane would fail within weeks.

The most common materials are polypropylene (PP) spun fibre and activated carbon block. PP cartridges remove physical sediment; carbon cartridges additionally remove chlorine, odour, and organic compounds.

• Traps rust, sand, silt, and sediment particles

• Extends the life of the RO membrane significantly

• Available in multiple micron ratings for different water qualities

• Easy to replace — typically every 3 to 6 months

Understanding Cartridge Filter Micron Size

A micron (also called a micrometre) is one-millionth of a metre. The micron rating of a cartridge filter tells you the size of the smallest particle it can reliably trap. The lower the micron number, the finer the filtration.

For reference: a human hair is about 70 microns wide. Bacteria range from 1 to 10 microns. Dust particles typically fall between 1 and 100 microns.

Most domestic RO purifiers use a 5 micron filter as the first or second stage pre-filter, followed by an activated carbon cartridge to remove chlorine and odour.

5 Micron Filter Explained

The 5 micron cartridge filter is the most widely used pre-filter cartridge for domestic RO systems across India. It strikes the ideal balance between fine filtration and adequate water flow for household use.

Benefits of a 5 Micron Filter

• Removes fine sediment invisible to the naked eye

• Protects the RO membrane from physical damage

• Suitable for both municipal water and mild borewell water

• Available as spun PP or carbon block in 10-inch and 20-inch sizes

• Affordable — one of the lowest-cost filtration components

Best Use Cases

• Domestic RO water purifiers (first or second stage)

• Areas with fine silt or rust in water supply

• Apartment complexes with overhead tank storage

• Small commercial RO systems

10 Micron Filter Explained

The 10 micron cartridge filter is the preferred choice when water is relatively clean and the priority is maintaining a high flow rate. It is less restrictive than a 5 micron filter, so water passes through faster, which matters for high-volume applications.

Benefits of a 10 Micron Filter

• Higher water flow rate than 5 micron filters

• Longer cartridge life in areas with moderate sediment

• Ideal as a first-stage coarse pre-filter before a 5 micron stage

• Lower initial pressure drop across the system

Best Use Cases

• Municipal water supply with low turbidity

• First-stage pre-filter in a dual pre-filter RO setup

• Commercial RO systems where flow rate is critical

• Areas with only coarse sediment (sand, debris)

5 Micron Filter vs 10 Micron Filter: Complete Comparison

Cartridge Filter Sizes Explained

Cartridge filters come in standard sizes designed to fit universal filter housings. The two most common sizes in India are the 10-inch and 20-inch cartridges.

10 Inch Cartridge Filter

The 10-inch cartridge filter is the most common size used in domestic RO water purifiers across India. It fits the standard slim-line filter housing found in most wall-mounted RO units. The actual length is approximately 9.75 inches (24.8 cm) to allow easy insertion and removal.

20 Inch Filter Cartridge

The 20-inch filter cartridge is used in commercial RO systems, industrial water treatment plants, and high-flow domestic setups. It offers twice the filtration surface area of a 10-inch cartridge, which means longer service life and higher flow capacity. It fits the standard big-blue housing used in most commercial pre-filtration systems.

Standard Dimensions

Pre Filter Cartridge for RO Water Purifiers

A pre-filter cartridge is any filter placed before the RO membrane in the water flow path. Its sole job is to protect the RO membrane from physical damage and chemical fouling.

Why Pre-Filtration Matters

The RO membrane is the most expensive component of any water purifier. It operates by forcing water through microscopic pores — pores so small that even dissolved salts are blocked. These pores are extremely vulnerable to physical particles, chlorine, and biological fouling.

• A good pre-filter extends RO membrane life from 1–2 years to 3–5 years

• Reduces system pressure drops and improves water output

• Prevents sediment from coating the membrane surface

• The carbon pre-filter removes chlorine, which chemically destroys the membrane

Standard Pre-Filtration Setup in Indian RO Systems

1. Stage 1 — PP Spun Sediment Cartridge (5 or 10 micron): removes large particles

2. Stage 2 — Granular Activated Carbon (GAC) Cartridge: removes chlorine and odour

3. Stage 3 — Carbon Block Cartridge (5 micron): fine pre-filtration before membrane

4. Stage 4 — RO Membrane: removes dissolved salts and heavy metals

Micron Cartridge Filter Price in India (2026)

Disclaimer: Prices listed above are approximate market estimates for 2026 and may vary based on brand, material quality, micron rating, quantity purchased, and supplier. Contact Pearl Water Technologies for current pricing and bulk discounts.

How to Choose the Right Cartridge Filter

Use this decision guide based on your water source and quality:

How Often Should You Replace a Cartridge Filter?

Cartridge filter lifespan depends on your water quality and usage volume. As a general rule:

• PP Spun Sediment Filter: every 3 to 6 months

• Carbon Block Filter: every 6 to 12 months

• Big Blue 20-inch filters: every 6 to 9 months (commercial use)

Signs Your Cartridge Filter Needs Replacement

• Reduced water output or slow filling of the storage tank

• Visible discolouration or brown/black colour of the filter cartridge

• Return of bad taste or odour in purified water

• Increased TDS reading in output water

• RO membrane pressure drop or frequent tank refills

Maintenance Tips

5. Mark the date of installation on the housing or a sticker

6. Check and replace filters every 3 months in areas with high sediment

7. Always use filters that match the housing size and thread type

8. Use a water quality test (TDS metre) to monitor output regularly

9. Do not over-tighten the housing — hand-tight is sufficient

Frequently Asked Questions (FAQs)

Q1. What is a 5 micron filter?

A 5 micron filter is a cartridge filter that traps all particles larger than 5 microns in diameter, including fine sand, silt, rust, and sediment. It is the most commonly used pre-filter in domestic RO water purifiers in India.

Q2. Is 5 micron better than 10 micron for RO purifiers?

Yes, for most Indian homes a 5 micron filter provides better membrane protection by catching finer particles. A 10 micron filter is suitable for cleaner water sources or as a first-stage pre-filter before the 5 micron stage.

Q3. What size cartridge filter do I need for my RO purifier?

Most domestic wall-mounted RO purifiers use the standard 10-inch (slim) cartridge. Check your existing cartridge or filter housing dimensions before purchasing. Commercial systems typically use 20-inch cartridges.

Q4. How long does a cartridge filter last?

A PP spun sediment cartridge lasts 3 to 6 months under normal use. Carbon block cartridges last 6 to 12 months. If your water has high sediment, replace more frequently — every 2 to 3 months.

Q5. What is the price of a 10-inch cartridge filter in India?

A 10-inch PP spun sediment filter cartridge costs approximately Rs. 35 to Rs. 100 in India, depending on brand and micron rating. Carbon block variants range from Rs. 100 to Rs. 250.

Q6. What is the difference between a sediment filter and a carbon filter cartridge?

A sediment filter (PP spun) removes physical particles like sand, rust, and silt. A carbon filter removes chemical contaminants including chlorine, taste, odour, and volatile organic compounds (VOCs). Both are used as pre-filters in RO systems.

Expert Recommendation from Pearl Water Technologies

Based on over a decade of supplying RO spare parts and filtration solutions across India, here is our expert guidance:

Always buy cartridge filters from a reliable supplier to ensure consistent micron rating accuracy, correct dimensions, and food-grade polypropylene material. Sub-standard filters may be labelled 5 micron but provide only 20–30 micron actual filtration — rendering your entire pre-filtration stage ineffective.

Conclusion

Choosing the right cartridge filter is not complicated once you understand what micron ratings mean and what your water quality demands. A 5 micron filter is the go-to choice for most Indian homes, offering reliable fine sediment removal and excellent RO membrane protection. A 10 micron filter works well for cleaner water sources or as a first-stage coarse pre-filter. For system sizing, the 10-inch cartridge handles domestic needs while the 20-inch cartridge serves commercial applications.

Key points to remember:

• Lower micron number = finer filtration = better membrane protection

• Replace PP spun filters every 3 to 6 months, carbon filters every 6 to 12 months

• Always match cartridge size to your housing — 10 inch or 20 inch