RO Water Filtration System Expansion Tank 6 Gallon - Compact RO

Our review of this RO water filtration expansion tank finds it to be a practical, no-nonsense upgrade for most under-sink reverse osmosis systems. The tank's biggest selling point is its combination of compact dimensions and sanitary materials: made from 100% food grade components, it stores filtered water without imparting odors or chemicals. Installation is straightforward thanks to the included 1/4' tank ball valve and 1/4' quick-connect compatibility, so homeowners replacing an old tank or adding extra on-demand capacity will see immediate benefits.

Key Features

• Food grade construction: The tank uses 100% food grade materials to keep stored water free from impurities and off-flavors for safe drinking.
• Compact size: With dimensions designed to fit under most sinks, the tank offers useful storage without requiring extra cabinet room.
• Included tank valve: A free 1/4' tank ball valve with quick-connect design simplifies replacement or installation and reduces plumbing time.
• Durable build: Deep-drawn steel domes and precision welding provide long-lasting structural integrity for the pressure vessel.
• Reliable testing and warranty: The tank is rigorously tested for quality and comes with a 1-year warranty for added peace of mind.
• Practical capacity: Although marketed as 6 gallon, the working stored water is about 4.4 gallons, which delivers several fills of standard pitchers or quick top-ups to 5-gallon containers.

Who It's For

This tank is aimed at homeowners with an existing reverse osmosis under-sink system who need a dependable replacement or a compact expansion reservoir. It suits kitchens where cabinet space is limited but consistent on-demand filtered water is required, and for users who value food-safe materials and a simple installation.

It is less appropriate for commercial installations or very large households that require much higher continuous flow or larger storage capacity; those buyers should consider larger, dedicated storage solutions or commercial-grade pressure vessels.

Pros & Cons

Pros

• Made from 100% food grade materials, helping preserve water taste and safety.
• Easy to install with the included 1/4' tank ball valve and quick-connect design.
• Compact footprint fits under most sinks while still providing around 4.4 gallons of usable water.
• Well-built steel construction and a 1-year warranty offer confidence in durability.

Cons

• Advertised as 6 gallon but usable capacity is about 4.4 gallons, which may confuse buyers expecting the full volume.
• Not suited for high-demand or commercial use where larger storage is required.

Specifications

Our Verdict

This expansion tank is a sensible, value-oriented choice for residential RO systems: its food grade construction, compact size and included valve make replacement or upgrade fast and reliable. For typical kitchen use and households seeking on-demand filtered water without extra space, it delivers good performance and durability at a fair price.

Frequently Asked Questions

Will this tank fit under a standard kitchen sink?
Yes; the compact dimensions (17.5 in x 12 in x 12 in) are designed to fit under most sinks.

Does the tank come ready to install?
It includes a 1/4' tank ball valve with quick-connect to simplify setup, though basic plumbing tools may still be needed.

How much water does it actually store?
Usable stored water is about 4.4 gallons, despite the 6 gallon model designation.