You hold a brown 10 inch cartridge over the sink. The housing sump drips in your other hand. You need to know which micron rating to put back in the line. The 20 micron water filter acts as the coarse first stage that stops sand and rust before the fine cartridge catches the rest. A clean coarse cartridge protects the fine cartridge behind it.

Water Filters FAST stocks the Hydronix SPC-25-1020 pleated cartridge. The store lists it at $7.99 today. This standard replacement fits typical residential housings. It traps heavy grit on a well line or ahead of a reverse osmosis system.

Written by the Water Filters FAST filter experts. Reviewed by Phil McNamara, owner, Water Filters FAST. Updated September 2026.

What a 20 micron water filter stops and passes

The micron rating system gives homeowners a clear way to measure filter performance. A micron equals one millionth of a meter. This tiny measurement defines filter sizes across the industry. A 20 micron nominal rating means the cartridge traps most particles that measure 20 microns and larger. The word nominal means most. It does not mean all.

The cartridge will catch most large pieces. It will let a few smaller pieces through into the water line. A lower micron number means a finer filter. This finer cartridge stops smaller particles. It clogs sooner on dirty water. A higher micron number means a coarser filter. A coarse filter passes fine particles. It holds more total dirt before it clogs. Sand and rust flakes count as sediment. Heavy grit also counts as sediment in a residential system. The coarse cartridge exists to stop these physical pieces before a finer cartridge takes over.

The Hydronix SPC-25-1020 uses four separate layers of filtration. The manufacturer builds these layers from 100 percent pure polypropylene. The listing says this graded density creates outside-in flow. The outer layers trap larger particles first. The inner layers catch the smaller pieces next. This layered design gives the cartridge a high dirt holding capacity.

The Hydronix SPC-25-1020 handles an initial flow rate of 8 GPM at 0.4 psi. It operates in water temperatures from 40 degrees Fahrenheit up to 145 degrees Fahrenheit.

Why the coarse cartridge goes first in the line

Many homes run a two-stage filter system on a well line. A well line often carries heavy dirt loads into the house. The coarse cartridge always sits in the first housing. A fine cartridge sitting alone catches everything in the water. That single fine cartridge clogs fast on dirty water. The water pressure drops off quickly.

A coarse first stage takes the heavy dirt load instead. The 20 micron water filter stops the big rust flakes. It catches the heavy sand. The water then flows to a fine second stage. When looking at a 5 micron vs 20 micron rating, the sequence matters greatly. The 5 micron stops smaller silt. The 20 micron stops the large sand beforehand.

The coarse filter protects the fine filter from early failure. This exact sequence helps a fine cartridge last a long time. It helps a reverse osmosis filter replacement schedule remain predictable. A clean coarse stage keeps the reverse osmosis membrane working well. The coarse cartridge exists to stop sediment before a reverse osmosis membrane has to. You place the coarse rating first to protect the membrane. You place the coarse rating first to save money on fine cartridges.

The housing read for your next cartridge

The physical check takes about two minutes. You shut the water supply to the housing. You relieve the line pressure. You open the sump. You pull out the old cartridge. You look at the pleats in the light. Coarse brown grit on the outside of the pleats tells a clear story. Rust flakes stuck to the polyester mean the filter works well. If the inside remains clean, the 20 micron first stage is doing its job.

A cartridge that clogs in weeks tells a different story. It might show a fine even brown film. This film means the water carries fine silt. That fine silt requires a second housing. A 5 micron cartridge placed after the 20 micron stage belongs in the line. A cartridge that stays almost clean after six months on a two-stage line means the first stage can change. You could move up to a 30 micron cartridge. You could move to a 50 micron cartridge.

The label on the old part overrules any table. Put back what the manufacturer recommends for your exact hardware. A pressure gauge across the housing gives the same answer in numbers. You can watch the gauge drop over time. The Hydronix listing says to change the cartridge when the pressure drop reaches 21.75 psi. The maximum pressure drop sits at 46.4 psi. You want to change the cartridge at the recommended point.

Comparing whole house sediment filter ratings

Water Filters FAST offers a full range of cartridges in the sediment water filters collection. You can match the exact micron rating to your specific water condition. The table below compares the different micron sizes for a standard 10 inch housing. It also includes one option for standard 20 inch housings.

The store lists the 50 micron 2.5 x 10 pleated polyester cartridge at $6.99 today. This cartridge acts as the first stage on gritty well water. The store lists the 30 micron 2.5 x 10 pleated polyester cartridge at $6.99 today. This cartridge also acts as the first stage on gritty well water.

The 20 micron sediment filter acts as the first stage for most homes. The 5 micron cartridge acts as the second stage. It can act as a single stage on city water ahead of a reverse osmosis system.

Pleated sediment filter design versus standard spun

A pleated sediment filter looks like an accordion. The pleats create a large surface area for the water to hit. The water spreads out over the entire polyester sheet. The Hydronix listing says the pleated design results in a much lower pressure drop compared to conventional filters.

The listing says the pleated polyester provides a much higher dirt holding capacity than standard spun polypropylene cartridges. It provides a higher capacity than string wound cartridges. This higher capacity means the pleated cartridge can hold more sand before the pressure drops. The graded layers trap various sized particles layer by layer.

The outside-in flow path keeps the core open longer. This flow path makes the pleated cartridge a fit for point-of-use applications. It suits residential reverse osmosis applications.

How to change a 2.5 x 10 sediment filter

These steps apply to a standard 10 inch whole house sediment filter housing. Follow this sequence to swap the cartridge safely.

1. Shut the supply line to stop the water flow to the housing.
2. Relieve the pressure at a downstream tap to make the housing easy to turn.
3. Unscrew the sump from the main filter head.
4. Lift out the old cartridge and set it in the sink.
5. Wipe the sump out with a clean cloth.
6. Seat the new cartridge directly on the center standpipe.
7. Check the o-ring is seated properly in its groove. Read how to change a whole house water filter for the o-ring trick.
8. Screw the sump back onto the head securely.
9. Open the supply slowly to let the housing fill with water.
10. Check the housing for drips around the rim.
11. Write the date on a piece of tape and stick it to the housing.

Calculating the annual filter replacement cost

Replacing two cartridges twice a year keeps a residential system running well. Clean cartridges keep the water pressure strong at the tap. Water Filters FAST lists the 20 micron Hydronix SPC-25-1020 at $7.99 today. This single cartridge provides an affordable first stage defense. The store lists the 5 micron 2.5 x 10 pleated polyester cartridge at $7.99 today. This cartridge provides an affordable second stage defense.

A 20 micron cartridge at $7.99 and a 5 micron cartridge at $7.99 cost $15.98 for a complete two-stage set. Changing that set twice a year costs $31.96 total. That is less than three dollars a month. A clean coarse filter saves the fine filter from early ruin. This habit saves money over the long term.

Some systems use longer housings to process more water. Standard 20 inch housings require longer cartridges. Water Filters FAST lists a 5 micron 2.5 x 20 pleated polyester cartridge at $14.99 today. This long filter fits 20 inch standard housings. The longer cartridge handles an initial flow rate of 14 GPM at 0.4 psi. The standard 10 inch version handles 8 GPM at 0.4 psi.

Common questions about sediment cartridges

What does a 20 micron water filter remove?

A 20 micron rating removes coarse sediment from residential water lines. The pleated polyester traps sand and rust flakes before they reach fine filters. The cartridge captures most particles measuring 20 microns and larger.

Is 20 micron finer than 5 micron?

A lower micron number means a finer filter. The 5 micron cartridge catches much smaller particles than the 20 micron cartridge. The 20 micron is coarser and lets more fine silt pass through.

Which comes first, 20 or 5 micron?

The 20 micron coarse cartridge always sits in the first housing. The 5 micron fine cartridge goes in the second housing. The coarse stage catches the heavy sand so the fine stage can catch the remaining silt.

How often do I change a sediment cartridge?

A visual inspection or a pressure gauge tells you when to change the cartridge. The listing recommends a replacement when the pressure drop reaches 21.75 psi. A cartridge coated in heavy brown sludge needs a change now to prevent a reverse osmosis slow flow problem downstream.

Does the 20 micron fit a standard 10 inch housing?

The Hydronix SPC-25-1020 measures 2.5 inches in diameter and 10 inches in length. This size fits standard residential 10 inch housings. It suits point-of-use and reverse osmosis lines.

Is the Hydronix cartridge NSF certified?

The listing says the Hydronix SPC-25-1020 is NSF Standard 42 component certified. The filter material uses 100 percent pure polypropylene. The cartridge handles a maximum operating temperature of 145 degrees Fahrenheit.

Order your replacement Hydronix sediment filter

Replace your old cartridge before the heavy pressure drop slows your system. Order the Hydronix SPC-25-1020 pleated sediment filter today. Water Filters FAST lists it at $7.99. Shipping is free over $75, and orders under that carry a $5 flat rate. A 30-day return policy and the Water Filters FAST satisfaction guarantee back every order. Call 855-789-FAST and the filter experts will confirm the match before you buy.