RO Water Holding Tank | 12L | Plastic

A 12L plastic permeate holding tank for residential reverse osmosis systems — the standard format for storing RO-purified water between membrane production and tap demand. Rust-free plastic shell (no metal corrosion concerns), pre-charged internal bladder, and includes the valve needed to connect to standard 1/4" RO tubing.

Why a Holding Tank Is Necessary for RO

Reverse osmosis is a slow process. A typical residential RO membrane produces 50-75 gallons per day (about 8-12 L/hr) — far slower than the rate at which you draw water from a tap.

Without a holding tank, every time you turn on the RO tap, you'd get a thin trickle straight from the membrane. With a holding tank, the system fills the tank in the background between uses, then the tank delivers water at normal tap-rate when you open the dispenser. The tank decouples production rate from demand rate.

Plastic vs Steel Holding Tanks

Most residential RO holding tanks are steel with internal bladders. This plastic alternative offers two distinct advantages:

• No external corrosion — humid under-sink environments don't rust a plastic tank shell
• Lighter weight — easier to handle during installation or replacement

The trade-off is lower pressure rating (100 PSI vs 125+ PSI on steel tanks) and smaller capacity at the same physical size. For most residential RO installations with under-50 PSI mains and household-scale demand, neither of these matter.

Specifications

• Total tank volume: 12 L (3.2 gallons)
• Actual water-holding volume: 9 L (2.4 gallons) — the remainder is air-side pre-charge
• Diameter: 24 cm
• Height: 35 cm (excluding fitting)
• Maximum working pressure: 100 PSI
• Construction: rust-free plastic shell with internal bladder
• Included: 1/4" valve for connection to 6mm (1/4") tube

The 9 L actual water-holding volume is the practical number — that's how much purified water sits in the tank ready for instant delivery. For most households, that's 4-6 jugs' worth, more than enough buffer for daily drinking and cooking demand.

Water-holding volume depends on supply pressure. Higher supply pressure compresses the bladder less, leaving more space for water; lower supply pressure leaves more bladder-side compression and less water capacity.

Where This Tank Fits

• Residential RO systems at 50-75 GPD production rate
• Replacement of a failed or punctured steel tank where plastic is preferred for corrosion resistance
• Compact installations where the 24 × 35 cm form factor fits available under-sink space
• Coastal and high-humidity homes where steel-shell tanks corrode externally over time