Taking care of your water filter — whether it’s a jug, a triple-housing system, or a reverse osmosis system — involves regular cleaning to remove biofilm and other contaminants. You can use a sponge and dishwashing detergent for this process.

Why does biofilm form

Even though municipal water is disinfected with chlorine, it can still contain certain bacteria as it travels through the pipeline. These bacteria are not harmful but can cause biofilm formation by attaching to the surface of filter components.

This explains why a water filter may turn black over time.

At the initial stage, biofilm appears as a green or rust-colored slimy layer, which can be easily removed with water and a sponge. If the buildup does not wash off this way, stronger cleaning agents may be required. For water filter pitchers, it’s usually best to replace the filter.

If mold or buildup forms on the outside of the filter, this is likely due to high humidity and mold growth in your home. The filter should be thoroughly cleaned externally using chlorine-based agents and/or baking soda.

Now, let’s discuss how to care for different types of filters.

Jug filter maintenance

The recommended lifespan of a pitcher filter is 5 years. To ensure optimal performance, replace the cartridges regularly and wash all components with dishwashing detergent every time you replace the filter element. The filter is dishwasher-safe.

With proper use, biological buildup should not be an issue.

Triple-housing filter maintenance

In flow-through filtration systems, biofilm can often form inside filter housings and tubing because these provide a favorable environment for bacterial growth. The lifespan of such systems is 5 years. Cartridge replacement should be done every 6 months, and the housings should be washed with dishwashing detergent during each replacement.

To ensure safety, it is recommended to disinfect the system by following these steps:

1. Turn off the water supply valve to the filter.
2. Open the faucet to release excess pressure.
3. Remove the used cartridges from the housings.
4. Screw back the second and third housings (without cartridges).
5. Add a disinfectant tablet or 50–60 ml of chlorine-based cleaner into the first housing, then screw it back.
6. Turn on the faucet first, then reopen the water supply.
7. When you detect a chlorine smell, turn off the water and faucet.
8. Let the system sit for 2–3 hours for disinfection.
9. Open both the drinking water and supply faucets and flush the system until the chlorine odor disappears.
10. Turn off the water supply again.
11. Wash your hands thoroughly and install a new set of filter cartridges.
12. Monitor the system for 2 hours to check for leaks.

Reverse osmosis filter maintenance and disinfection

Just like triple-housing filters, reverse osmosis (RO) systems can develop microbial biofilm, particularly in pre-filter housings, waste drain tubing, and, less commonly, on the membrane surface or storage tank after prolonged use. Mineralizers and post-filters are rarely affected since they receive already purified water.

To prevent such issues, disinfect the system every six months by following these steps:

1. Shut off the water supply to the filter and storage tank.
2. Drain the remaining water from the system and remove the pre-filter cartridges.
3. Use pliers to carefully remove the reverse osmosis membrane and store it in the refrigerator.
4. Reinstall the second and third filter housings (without cartridges).
5. Disconnect the post-filter tube and attach it directly to the system’s T-connector.
6. Add a chlorine tablet or 50–60 ml of chlorine-based bleach to the first housing, then screw it back.
7. Wait 15 minutes, then turn on the water supply and faucet.
8. When you detect a chlorine odor, turn off all faucets and let the system sit for 2–3 hours.
9. Flush the system by opening the faucet and waiting until the chlorine smell disappears.
10. Reinstall all filter elements and turn the water supply back on.
11. Flush 14–20 liters of water (at least two full tank cycles).

Storage tank disinfection

The storage tank can be disinfected together with the whole system or separately. To disinfect it alone:

1. Turn off the water supply to the filter and drain any remaining water.
2. Shut off the tank valve.
3. Remove the pre-filter cartridges and reinstall the second and third housings.
4. Disconnect the tank tube from the T-connector and attach it to the outlet of the third filter housing.
5. Add a chlorine tablet into the first filter housing, wait 15 minutes, and then turn on the faucet for 5–7 minutes.
6. Shut off the tank valve and let it sit for 2 hours.
7. Disconnect the tube from the third housing and drain the tank completely.
8. Reassemble the system, reinstall the cartridges, and restore normal tubing connections.
9. Flush 24–50 liters of water (at least three full tank cycles).

Besides regular six-month disinfection, the system should also be sanitized after more than two weeks of inactivity.

By performing timely disinfection and replacing filter cartridges as needed, you can prevent biofilm buildup on filter components and ensure clean, safe water.