How to Clean a Reverse Osmosis Storage Tank

Essential Steps for Tank Sanitization and Bacterial Prevention

Regular cleaning of your reverse osmosis storage tank is crucial for maintaining water quality, preventing bacterial growth, and ensuring your system operates at peak performance. Whether you have a pressurized bladder tank under your sink or a large atmospheric storage tank for whole-house systems, this comprehensive guide walks you through the complete cleaning process step by step.

When to Clean Your RO Storage Tank

• Annually: Sanitize both bladder and atmospheric tanks once a year for routine maintenance
• After Repairs: Always clean your tank after system maintenance or if it has been left unused
• Signs of Contamination: Clean immediately if you notice odd smells, bad taste, cloudy water, or visible sediment
• Extended Downtime: Clean before restarting if the system has been inactive for more than 2 weeks

Safety Precautions Before You Start

• Always wear gloves and safety goggles when handling cleaning chemicals
• Use only unscented household bleach (5-6% sodium hypochlorite) or NSF-certified sanitizers
• Ensure adequate ventilation when working with bleach solutions
• Never enter large tanks without proper confined space safety training
• Disconnect power to pumps and electrical components before cleaning

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Cleaning an Atmospheric RO Storage Tank (Large Capacity Tanks)

Atmospheric storage tanks, commonly ranging from 165 to 1,000+ gallons, are used in commercial, industrial, and whole-house RO systems. These open-to-atmosphere tanks require thorough cleaning to prevent sediment buildup, scale formation, and bacterial growth. View Crystal Quest's complete water storage tank collection to find the right size for your needs.

1. Prepare for Cleaning

1. Turn off the water supply to the tank and RO system
2. Drain the tank as much as possible using existing valves or a sump pump
3. Power down any connected pumps or electrical components for safety
4. Gather necessary supplies: wet/dry vacuum, long-handled brush, bleach, and clean water source

2. Fully Drain and Remove Debris

Use a wet/dry vacuum or sump pump to remove all remaining water and any sludge or sediment from the tank bottom. This step is crucial as debris can harbor bacteria and reduce the effectiveness of sanitization. Remove as much physical contamination as possible before proceeding.

3. Physically Clean the Interior

If your tank has an inspection port or access hatch:

1. Scrub interior walls and bottom using a long-handled brush or pressure washer
2. Pay special attention to corners, seams, and areas around fittings where biofilm tends to accumulate
3. Rinse thoroughly with clean water and vacuum out all rinse water

4. Disinfect the Tank

Proper disinfection is critical for eliminating bacteria, viruses, and other microorganisms. Use this bleach calculation for effective sanitization:

Fill the tank with clean water after adding bleach, ensuring the solution contacts all interior surfaces. Let the solution sit for at least 6 hours, preferably overnight. Open outlet valves periodically to circulate chlorinated water through connected plumbing lines.

5. Rinse and Flush Thoroughly

1. Drain all chlorinated water away from landscaping, gardens, or septic systems
2. Refill the tank with clean water and drain completely—repeat at least twice
3. Continue flushing until there is no detectable chlorine smell
4. Flush all connected pipes, valves, and distribution points
5. Consider using chlorine test strips to verify complete removal (should read 0 ppm)

6. Reconnect and Restart

Once thoroughly rinsed, reconnect all plumbing connections and restart the RO system. Allow the tank to fill completely and run through one or two full cycles before resuming normal use. Test the water quality to ensure proper system operation.

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Cleaning a Pressurized Bladder Tank (Under-Sink Systems)

Bladder tanks, typically 3-4 gallons in residential RO systems, contain a flexible diaphragm that separates water from compressed air. While enclosed, these tanks can still harbor bacterial growth and should be sanitized annually to maintain water quality.

1. Shut Down and Drain the Tank

• Turn off the water supply valve to the RO system
• Open the RO faucet and keep it open until water stops flowing
• Ensure the tank is completely depressurized and empty

2. Remove Filters and Membrane

To protect sensitive filtration components from bleach damage:

1. Remove all pre-filters (sediment and carbon)
2. Carefully remove the RO membrane from its housing
3. Remove the post-carbon filter if present
4. Store these components in a clean, dry place during sanitization

3. Add Sanitizing Solution

For a standard 3-4 gallon bladder tank, use one of these sanitizing options:

• Bleach Method: Mix 1-2 teaspoons of unscented household bleach with 1 gallon of water
• Commercial Sanitizer: Use an NSF-certified sanitizer specifically designed for water storage tanks, following package directions

Pour or inject the solution into the system through the filter housing or tank valve opening. For precise application, use a funnel or large syringe.

4. Circulate and Let It Sit

• Turn the water supply back on briefly to allow some water to enter and mix with the sanitizer
• Turn off the supply once you hear water entering the tank
• Let the sanitizing solution sit for 15-30 minutes to disinfect all internal surfaces
• Rock or gently shake smaller tanks to ensure complete coverage

5. Flush and Rinse Thoroughly

1. Open the RO faucet to drain the sanitized water completely
2. Turn on the water supply to refill the tank
3. Drain and refill at least 2-3 times until no chlorine odor remains
4. The final rinse water should taste and smell completely neutral

6. Reinstall Components and Resume Use

Once thoroughly flushed:

1. Reinstall all filters in the correct order
2. Carefully reinstall the RO membrane, ensuring proper orientation
3. Turn the system back on and check for leaks
4. Allow the tank to fill completely before first use
5. Discard the first tank of water as an extra precaution

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Troubleshooting Common Tank Issues

Problem	Likely Cause	Solution
Musty or swampy odor	Bacterial growth in tank	Sanitize tank immediately following procedures above
Low water pressure	Low air pressure in bladder tank	Check and adjust air pressure to 7-10 psi when empty
Tank won't fill	Ruptured bladder or faulty check valve	Replace tank or check valve as needed
Cloudy or milky water	Air in system or bacterial bloom	Flush system; sanitize if problem persists

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Maintaining Your Complete RO System

Tank cleaning is essential, but it's only one component of complete RO system care. To maintain peak performance, you'll also need to replace your RO membrane(s) every 2-4 years, clean your membrane(s) when flow rates decline, and replace pre and post filters every 12-24 months to protect your entire system.

For a detailed maintenance schedule and troubleshooting tips, explore our complete RO maintenance guide. Whether you're sanitizing a compact under-sink bladder tank or maintaining a large atmospheric storage system, regular cleaning prevents costly repairs and protects your investment in clean water.

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Keep Your Water Pure with Regular Tank Maintenance

A clean storage tank is the foundation of a healthy reverse osmosis system. By following these cleaning procedures annually—or whenever you notice signs of contamination—you'll ensure your RO system continues delivering the pure, fresh-tasting water your family depends on. Remember, the time invested in proper tank maintenance pays dividends in system longevity, consistent water quality, and peace of mind.