Total Volume
3.2 gal (12 L)
Includes
Tank + Stand + Valve
A compact RO storage tank kit — PAE’s standard 3.2-gallon (12 L) steel tank holds about 2–2.2 gallons of ready-to-use RO water in a slim 8.5″-wide body, and comes with a tank stand and a free 1/4″ ball valve. The easy replacement for a worn-out 3.2-gallon tank, or a fit for tight under-sink cabinets.
What it is
This is a pressurized RO storage tank for under-sink reverse osmosis systems. An RO membrane makes water slowly, so the tank stores it under air pressure and delivers it on demand. You get a steady stream at the RO faucet instead of a trickle.
The RO-122 is the standard 3.2-gallon size that most under-sink RO systems ship with: 12 liters nominal volume, holding about 2–2.2 gallons of usable water depending on your line pressure. At about 15″ tall and 8.5″ in diameter, it fits cabinets where a full-size tank won’t.
It ships as a ready-to-install kit: the tank, a matching stand that keeps it upright and off the cabinet floor, and a 1/4″ ball valve that threads onto the tank’s top port so you can shut it off for filter changes. Made in Taiwan by TankPAC Industries / Global Water Solutions under the PA-E® brand, and listed by NSF to NSF/ANSI 58 as an RO storage tank component.
What’s included
- ✓PAE RO-122 pressurized storage tank — 3.2 gal (12 L) nominal, about 2–2.2 gal usable; steel shell, food-grade butyl bladder, white powder-coated finish, pre-charged at the factory
- ✓Tank stand — keeps the tank upright and stable under the sink
- ✓FREE 1/4″ tank ball valve — threads onto the tank’s top port (1/4″ FPT × 1/4″ tube quick-connect)
Key benefits
- ✓Compact size — about 15″ tall × 8.5″ wide, for tight under-sink cabinets
- ✓Standard 3.2-gallon size — the easy replacement for a worn-out tank; about 2–2.2 gallons ready at the faucet
- ✓NSF/ANSI 58 certified tank component — genuine PA-E TankPAC, made in Taiwan
- ✓Complete kit — tank + stand + free valve in one purchase, ready to install
- ✓Food-grade bladder — keeps stored water separate from the air charge
- ✓Standard 1/4″ NPT port — fits most residential under-sink RO systems
- ✓Rated 100 PSI, factory-tested to 144 PSI — steel shell with a white powder-coated finish
- ✓Double-boxed — the factory box ships inside a second shipping box for extra protection
How it works
The tank uses a pressurized bladder system. The air side (pre-charged to 7 PSI at the factory) pushes against the water side of the bladder. As your RO system makes water, it fills the bladder and compresses the air. When you open the faucet, the compressed air pushes the stored water out, so you get steady flow right away.
The auto shut-off valve in your RO system senses when the tank is full and stops production. When you draw water and the pressure drops, the system starts making water again automatically.
Specifications
| Brand / model |
PAE TankPAC RO-122 (type MTRA-12-7) |
| Tank type |
Pressurized RO storage tank (bladder type) |
| Nominal volume |
3.2 gallons (12 liters) |
| Usable water |
About 2–2.2 gallons (varies with line pressure) |
| Factory air pre-charge |
7 PSI (0.5 bar) |
| Max working pressure |
100 PSI (6.9 bar) |
| Factory test pressure |
144 PSI (9.9 bar) |
| Water temperature (label) |
40–122°F (4–50°C) — for RO water storage |
| Tank connection |
1/4″ NPT male thread (top port) |
| Ball valve (included) |
1/4″ FPT × 1/4″ tube quick-connect |
| Air charge valve |
Schrader valve on the side, near the bottom (under the blue cap) |
| Shell / interior |
Steel, white powder coat / food-grade butyl bladder |
| Dimensions (approx.) |
15″ tall × 8.5″ diameter |
| Certifications |
NSF/ANSI 58 (storage tank component), CE |
| Manufacturer |
TankPAC Industries / Global Water Solutions, Taiwan |
| SKU / MPN |
RO-TANK-122 / RO-122 |
Installation
- Check the air pre-charge first with the tank empty: about 7 PSI on a tire gauge at the Schrader valve (under the blue cap). Adjust with a bicycle pump if needed.
- Place the tank on the included stand under the sink, near the RO system.
- Thread on the ball valve: wrap the tank’s 1/4″ NPT port with PTFE tape (3–4 wraps), then hand-tighten plus about 1/4 turn with a wrench. Don’t overtighten.
- Connect 1/4″ tubing from the RO system’s tank tee to the valve’s quick-connect port.
- Open the ball valve and let the system fill the tank. The first fill can take several hours, depending on membrane size and water pressure.
- Drain the first full tank to flush the system before use.
The manufacturer recommends professional installation.
Maintenance tip
If flow at the faucet gets weak even though the tank feels heavy (full of water), the air pre-charge may have dropped. Close the ball valve, drain the tank through the faucet until it’s empty, then re-pressurize the air side to about 7 PSI through the Schrader valve with a bicycle pump. This restores the “push” that delivers water to the faucet.
Often used with
Under-Sink RO Parts
Fittings, valves & accessories
View parts →
Need more water on hand?
Full-size PAE RO-132 — 4.8 gal, about 3.5 gal usable
View RO-132 →
Please note: This tank stores water made by your RO system; it does not filter or treat water itself. The NSF/ANSI 58 certification applies to this tank as a component, not to a complete RO system. Usable volume is less than nominal volume because the air side of the bladder takes up part of the tank, and it depends on your incoming water pressure. The tank is pre-charged at the factory, but the air pressure may need adjusting after shipping. For RO storage use only — not a well or general-purpose pressure tank. If surface corrosion appears, replace the tank.
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