Reverse Osmosis Water Storage Tanks

Reverse osmosis storage tanks hold purified water until it’s needed. Fresh Water Systems carries water storage tanks for homes, cafés, breweries, laboratories, and light industrial use. 

Types of Reverse Osmosis Storage Tanks 

Pressurized Diaphragm Tanks 

Standard residential RO storage tanks are hydropneumatic pressure tanks, with a flexible diaphragm separating purified water from compressed air. When the faucet opens, air pressure delivers water without external power, maintaining steady water pressure. These osmosis tanks provide immediate flow while the membrane filters slowly. Common capacities range from two to 40 gallons; pre-charge pressure and usable capacity vary from model to model. 

Metal, Stainless-Steel and Composite Tanks 

Powder-coated steel tanks are commonly seen underneath sinks, while stainless-steel models suit high-purity applications and fiberglass-reinforced composite tanks work well in corrosive environments. Many reverse osmosis tanks use food-grade diaphragms or polypropylene liners, with select models carrying NSF/ANSI 58 certification. 

High-Capacity Commercial Tanks 

Commercial water storage tanks bridge the gap between slow membrane production and peak demand. Cafés, breweries, labs, and industrial settings need larger pressurized osmosis tanks to power equipment and limit cycling. While atmospheric tanks offer high-volume storage, these vented vessels also require a delivery pump. 

How to Choose the Right Reverse Osmosis Storage Tank 

Prioritize the usable capacity, daily consumption, and peak flow. Listed volume is the total internal volume, so the available water is lower and will change with feed pressure and pre-charge. A common 4.5-gallon model is about 11 inches in diameter and rated for up to 100 psi; a 14-gallon option measures roughly 15 inches wide by 23 inches high. 

Confirm the working pressure, wetted materials, certification, and connection size. Match the threaded inlet and shutoff valve to the tubing, including any 1/4-inch or 3/8-inch quick-connect fittings. Carefully measure the installation area and leave enough room to reach the valve. For commercial reverse osmosis, compare tank drawdown to system production, peak demand, and pressure requirements. 

Installation and Maintenance Tips 

Shut off the feed water and relieve system pressure before installing. Check pre-charge only when the tank is empty; 5 to 7 psi is typical for residential tanks, but always follow the manufacturer’s settings.  

After connecting the valve and tubing, restore the water and inspect the fittings. Continue to check the pressure periodically, and look out for low flow, reduced capacity, or water at the air valve. 

Frequently Asked Questions About RO Storage Tanks 

What is the best tank for storing RO water?  

The best reverse osmosis storage tank has enough capacity for peak demand, compatible pressure and connections, and food-grade wetted materials. Homes usually use pressurized diaphragm tanks; large systems might need composite or atmospheric storage. 

Do you need a storage tank for reverse osmosis?  

Most conventional systems do, considering that the membrane produces water at a low real-time flow rate. With the tank, there’s a buffer between production and use. Tankless systems use different designs, though, so follow the requirements of your system. 

How long does an RO storage tank typically last?  

Many tanks last for a decade or longer, although usage and diaphragm wear affect the service life. Replace the tank when water comes from the air valve, the shell leaks, or repressurizing no longer restores flow. 

Tank Accessories and Support 

Complete your setup with a compatible tank valve, pressure gauge, fittings, or sanitizing supplies. Contact us for help sizing tanks or for custom quotes and bulk pricing.