Best CTO Under-sink Filters of 2026

Jennifer Fraser Avatar
Jennifer Fraser
Last Updated: 4 Feb 2026

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CTO Under-sink Filters are a type of water filtration system designed to remove impurities and improve the taste and quality of drinking water. These filters are installed under the sink and are connected to the cold water line, providing filtered water directly from the tap. CTO filters are known for their effectiveness in removing chlorine, sediment, and other contaminants from the water, resulting in a fresh and clean taste. They are easy to install and maintain, making them a popular choice for households looking to upgrade their drinking water.

At a Glance: Our Top Picks

iSpring US31 Classic 3-Stage Water Filter System Cover #TOP 1
iSpring US31 Classic 3-Stage Water Filter System
ftb score rating icon 9.8
iSpring WGB21B 2-Stage Water Filtration System Cover #TOP 2
iSpring WGB21B 2-Stage Water Filtration System
ftb score rating icon 9.7
iSpring WGB21B-KS Whole House Water Filter Cover #TOP 3
iSpring WGB21B-KS Whole House Water Filter
ftb score rating icon 9.5

Top 4 CTO Under-sink Filters

#TOP 1

iSpring US31 Classic 3-Stage Water Filter System

US31
iSpring US31 Classic 3-Stage Water Filter System Cover
iSpring US31 Classic 3-Stage Under Sink Water Filtration System for Drinking, Tankless, High Capacity, Sediment + GAC + CTO (Newest Version)

The iSpring US31 Filter System offers a three-stage purification process that effectively removes sediments, heavy metals, and harmful chemicals from your drinking water. With its impressive flow rate, it can meet all your household needs, providing fresh and clean water directly from your tap. The elegant European-designed faucet and clear first-stage housing make it easy to inspect filters, ensuring your system remains in top condition. Designed for simple installation and low maintenance, you can enjoy delicious, healthy water with minimal effort.

What We Like
Effective three-stage filtration
Fast flow rate
Stylish design
Easy installation
Low maintenance
#TOP 2

iSpring WGB21B 2-Stage Water Filtration System

WGB21B
Blue, Black
iSpring WGB21B 2-Stage Water Filtration System Cover
iSpring WGB21B 2-Stage Whole House Water Filtration System, with 10" x 4.5" Sediment CTO(Chlorine, Taste, and Odor) Filter, 1" Inlet/Outlet

The iSpring WGB21B Filter offers two-stage effective filtration to ensure your water is clean and fresh. The first stage captures various particles like dirt and rust, while the second stage removes over 90% of chlorine and unpleasant tastes and odours. With a superb filtration capacity, it can provide up to 50,000 gallons of purified water, which is ideal for a family of four. Additionally, it retains valuable minerals, ensuring that you enjoy healthy water without sacrificing essential nutrients.

What We Like
Highly effective two-stage filtration
Long-lasting filter capacity
Retains essential minerals
Fast water flow
Easy filter changes
#TOP 3

iSpring WGB21B-KS Whole House Water Filter

iSpring WGB21B-KS Whole House Water Filter Cover
iSpring WGB21B-KS 2-Stage Whole House Water Filtration System with 10" x 4.5" Sediment CTO(Chlorine, Taste and Odor) Filter,KDF+GAC filter, Removes Chlorine, Iron, Lead, Odor and More, 1" Inlet/Outlet

The iSpring WGB21B-KS Filter offers a comprehensive solution for your home's water needs. With its high capacity filters, you can enjoy cleaner water by effectively removing up to 99% of harmful contaminants, including chlorine and lead. The system guarantees great water flow, providing up to 15 gallons per minute, ensuring you won’t experience any disruptions during use. Constructed from high-quality materials, the filters are designed for optimal performance and longevity, making your water taste better while eliminating unpleasant odours.

What We Like
Removes up to 99% contaminants
High water flow rate
Durable, quality materials
Easy filter changes
Maintains healthy minerals
#TOP 4

iFilters Whole House Water Filter System

LWH-D
Multicolored
iFilters Whole House Water Filter System Cover
iFilters Whole House Water Filter, 2 Stage, Removes Sediment, CTO, and More, Minimal Pressure Drop, City and Well Water

The iFilters Water Filter is designed to enhance your home's water quality by filtering out sediment, dirt, and rust, ensuring that you enjoy cleaner and safer water. It effectively reduces chlorine taste and odour, making your drinking water more pleasant. By using this filter, you can extend the life of your washing machines and water heaters, saving you money on repairs and replacements. Its easy-to-use design features a 3/4" NPT port with a pressure relief button, simplifying filter changes for your convenience.

What We Like
Removes sediment and dirt
Improves taste and odour
Extends appliance lifespan
Easy filter replacements
Buying Guide Image

Frequently Asked Questions (FAQs)

1. What is CTO in filter?

CTO is an acronym for Chlorine, Taste, and Odor. A filter recommended for CTO removal will produce water that is much clearer in color with a more appealing taste and elimination of odors.

2. What is CTO cartridge?

100% brand new and high quality carbon block CTO water filter cartridges are used in reverse osmosis systems and other water filtration systems, For removal of Chlorine – Chemicals Bad Taste and Odor PCB's – Dirt – Sediment Rust – Algae.

3. How long do under sink water filters last?

When you're considering the overall investment of an under-sink water filter, think of the lifespan of its filters. Some last as little as three months, whereas others can last six to 12 months.

Editor's Notes

During our cto under-sink filter research, we found 15 cto under-sink filter products and shortlisted 4 quality products. We collected and analyzed 69,306 customer reviews through our big data system to write the cto under-sink filters list. We found that most customers choose cto under-sink filters with an average price of £154.52.

The cto under-sink filters are available for purchase. We have researched hundreds of brands and picked the top brands of cto under-sink filters, including iSpring, iFilters.

Written by
Jennifer Fraser Avatar

Jennifer Fraser is a licensed contractor specializing in sales, maintenance, and kitchen, bathroom, and home appliances, tools, and utilities. She owns a store in Leeds where you can get any home and tool appliance. Jenny has a degree in literature, but she combines her knowledge and experience with her degree to publish DIY articles on solving home appliances issues to keep up the family enterprise.