Cartridge vs bag filter — which to choose?

Cartridge filters give tight, absolute micron ratings (down to ~0.1 µm with membrane) for polishing and final clarification. Bag filters hold more dirt and need fewer changeouts, suiting coarser removal and higher solids at lower cost per litre.

When should I use a self-cleaning strainer?

Use a self-cleaning strainer or filter on continuous, high-volume lines where manual changeout is costly or impractical. Automated backflush removes screen-captured solids with minimal downtime and consumable use.

How do I specify micron rating?

Match the rating to the largest particle your downstream process can tolerate — e.g. pre-filter at 50–100 µm ahead of a 5–10 µm polishing stage, or <1 µm membrane for sterile/ultra-pure duty. Tighter ratings raise ΔP and changeout frequency.

KOSA Filter · Application Engineering

Liquid Filtration Selection Guide

Q: What is liquid filtration and what is it used for?

Liquid filtration removes suspended solids from water, chemicals, solvents, oils and food streams to protect equipment, clarify product and meet quality specs. It is used in water treatment, chemical processing, food & beverage, and pre-filtration ahead of membranes/ROI.

A practical checklist for specifying liquid filters across water, chemical and food lines — with a side-by-side comparison, micron ratings and a 4-question selector.

Key Takeaways

Liquid filtration removes suspended solids to protect equipment and clarify product.
Cartridge = tight absolute micron ratings for polishing; bag = high dirt-holding, fewer changeouts.
Self-cleaning strainer = continuous duty with automated backflush, low consumables.
Stage filtration: coarse pre-filter → fine polish → membrane for ultra-pure.
Size by flow, viscosity, target micron and allowable ΔP.

What liquid filtration is — and where it is used

Liquid filtration is the removal of suspended solids from water, chemicals, solvents, oils and food streams to protect equipment, clarify product and meet quality specs.

It is used in water treatment, chemical processing, food & beverage, and as pre-filtration ahead of membranes/ROI. Correct staging protects expensive downstream assets and holds product quality.

Liquid filter types compared

The table compares cartridge, bag and self-cleaning strainers on the criteria buyers weigh — rating, flow and best-fit duty.

Type	Rating	Flow	Changeout	Best for
Cartridge	0.1–50 µm (absolute)	Low–medium	Manual	Polishing, final clarification
Bag	1–200 µm	Medium–high	Manual (fewer)	High dirt-holding, lower cost/L
Self-cleaning strainer	10–300 µm (screen)	Medium–high	Automated backflush	Continuous/unattended duty
Membrane	<0.1 µm	Low	Manual	Sterile / ultra-pure

Ratings are typical; final selection depends on media, housing and certification. Confirm against your process data.

How to size a liquid filter

Flow: size housing for peak m³/h; stage coarse→fine.
Micron: set by downstream tolerance (pre 50–100 µm → polish 5–10 µm → membrane <1 µm).
ΔP: tighter ratings raise ΔP and changeout frequency — balance cost vs purity.
Media: PP/PTFE/nylon/SS; match chemical compatibility.

4-question selector

1. What purity do you need?

Clarify → bag/cartridge. Ultra-pure/sterile → membrane.

2. How much solids loading?

High → bag or self-cleaning. Low/final → cartridge.

3. Batch or continuous?

Continuous → self-cleaning strainer. Batch → bag/cartridge.

4. What chemical class?

Match media and seals to pH/solvent/temperature; request compatibility data.

How we evaluated these recommendations

Based on KOSA Filter's liquid filtration range and typical calls from water, chemical and food teams, cross-checked against common filtration practice. Authored by the KOSA Filter application-engineering team — connect on LinkedIn. Confirm against your P&ID and process data.

Need a tailored filtration quote?

Talk to KOSA Filter engineers about flow, micron rating and duty.

Request a quote