It can be frustrating to invest in a filtration system and still experience unpleasant-tasting water. Although RO (Reverse Osmosis) systems remove up to 99% of contaminants, factors such as maintenance and water chemistry can affect the final taste.
Below is an overview of common reasons for poor-tasting RO water and recommended solutions.
Common reasons for poor-tasting RO water
1. Expired or Clogged Filters
The most frequent cause is filters that have reached the end of their lifespan. Most RO systems include three filtration stages before water reaches the membrane.
- Carbon Filters: These remove chlorine and organic compounds that cause unpleasant odors and tastes. If the carbon is depleted, these contaminants remain in the water.
- Sediment Filters: Clogged sediment filters reduce water pressure, which can compromise system performance and water quality.
- Post-Carbon Filter: This final filter improves taste. Metallic or earthy flavors at the faucet often indicate it needs replacement.
2. A Compromised RO Membrane
The membrane is central to the system. If it is damaged or worn, dissolved solids may pass through, resulting in poor water quality.
- Torn Membrane: Even a small tear can allow salts, minerals, and chemicals to bypass filtration.
- Scale Buildup: In hard water areas, calcium deposits can reduce membrane effectiveness and alter water taste.
3. Issues with the RO Storage Tank
RO water is typically stored in a pressurized tank for extended periods before use.
- Stagnant Water: Infrequent use can cause water to develop a flat or plastic taste due to the tank’s rubber bladder.
- Biofilm Growth: Over time, bacteria can form a biofilm inside the tank or delivery tubes, resulting in a musty or swampy taste.
- Degraded Bladder: A deteriorating internal rubber bladder can cause a chemical or rubbery flavor in the water.
4. The “Flat” Taste (Low Minerals)
RO water may taste unpleasant because it is highly purified.
- Demineralisation: Removing minerals such as calcium, magnesium, and potassium can result in water that tastes flat, bitter, or metallic.
- pH Level: RO water is usually slightly acidic, which can give it a sharper or more sour taste than neutral or alkaline tap water.
5. Foul Odors and Their Likely Causes
In some cases, the specific taste can help identify the underlying issue:
| Rotten Eggs (Sulfur) | Bacteria in the storage tank or a spent carbon filter. |
| Metallic/Copper | Highly acidic water leaching metal from your pipes or an old membrane. |
| Salty | A ruptured RO membrane allowing dissolved salts to pass through. |
| Chlorine/Bleach | Failed pre-carbon filters that are no longer neutralizing chlorine. |
How to Fix It
- Flush the System: If the system has not been used recently, drain the storage tank twice and allow it to refill.
- Sanitise: Use an RO sanitation kit or a small amount of food-grade hydrogen peroxide or bleach, following manufacturer instructions, to clean the tank and lines.
- Check the TDS: Use a handheld TDS meter to test the water. If the reading is similar to your tap water, replace the membrane.
- Add a Remineralizer: If the water tastes flat, install an alkaline remineralization filter after the RO membrane to restore beneficial minerals.
