Why Does Reverse Osmosis Water Tastes Bitter?

Why Does Reverse Osmosis Water Tastes Bitter?

Reverse Osmosis (RO) water, or for that matter water from any other water filtration device, tastes different compared to regular tap water. The removal of contaminants, chemicals, and minerals results in a taste change, but in a good way. However, sometimes the water tastes bitter. Why? Let’s find out.

Bitter reverse osmosis water is an indication of a faulty RO system. The bitterness could be the result of copper corrosion, high pH levels, reduced concentration of minerals, a damaged membrane, or expired filters.

Reverse osmosis is a multifaceted system and there’s more than one problem that can cause the water to taste bitter. Pinpointing the problem can expedite the repair process, and help you get better-tasting water, faster. In this article, we’ll discover some of the main culprits of bitter water and how to fix them.

Read my comprehensive article about reverse osmosis.

Top Reasons Behind Bitter Tasting RO Water

Bitter-tasting water is not only unpleasant to drink but also impacts cooking, brushing teeth, coffee, and bathing. This detailed guide will help you figure out what could be causing your RO water to taste bitter and how you can get it to taste as it should.

Read my other articles about the taste and quality of reverse osmosis water.
Why Does Reverse Osmosis Water Tastes Metallic?
Why Does My RO Water Smell?
Making Coffee with Reverse Osmosis Water: Tasty or Awful

1. Copper pipes corroding

Many reverse osmosis systems are fitted with copper tubes, which impart a metallic taste to the water, making it bitter. Reverse osmosis water is extremely clean and pure and has an affinity to leach minerals from its surroundings, which in this case will be copper. Not only does this create bitter tasting water, but it also means the tubing itself develops pinhole leaks over time.

Read my article about reverse osmosis treated water corroding pipes.


The best type of tubing for RO systems is cross-linked polyethylene (PEX). It lasts a long time and is resistant to corrosion and leaking, caused by water contaminants. Replace your copper tubes with PEX to avoid bitter tasting water now and in the future.

2. Clogged reverse osmosis membrane

Although a reverse osmosis system comprises multiple filters, it is the semi-permeable membrane that gives it a 90% contaminant-free reputation.

The membrane has pores of 0.0001 microns, and it catches large amounts of impurities. As a result, it gets clogged quickly and needs regular replacement.

If your RO system has a clogged membrane then it will fail to purify water, leaving numerous dissolved solids in it, and making the water taste bitter.

Read my article about the importance of maintaining your reverse osmosis system.


Replace the semi-permeable membrane once every 2 years, and replace all the other filters in 6 to 12 months to avoid ever having to deal with bitter water. These are necessary maintenance procedures of an RO system and must be done to ensure high-quality water.

3. Sulfur concentration is high

High concentration of sulfur also leaves a bitter after-taste in the water. In perfect working condition, it is the semi-permeable membrane and the granular activated carbon filter that eliminates sulfur from the water.

If after a water test you find the bitter taste in the water is due to high levels of sulfur, it’s likely that either the filters or the membrane have reached the end of their useful lives and need a replacement.

If this sulfur-induced water is left to sit for a long time, it will start to smell like rotten eggs.


Replace the carbon filter and if the problem persists, invest in a new semi-permeable membrane.

4. Low mineral concentration

The absence of calcium is a common reason behind bitter-tasting water. Since RO eliminates 90% of the dissolved solids from the water, many minerals end up being filtered too. Calcium is one of them.


Numerous minerals in water are good for our health and the taste of the water. To solve this issue, a remineralization filter can be fitted into the system. Many RO systems come with built-in mineralizers that deposit essential minerals back into the water after purification.

Read my article about remineralizing reverse osmosis treated water.

5. Dissolved salts and solids

The dissolved salts and solids in the water add a salty and sour flavor. A functioning RO system should be able to eliminate all types of total dissolved solids (TDS) from the water. If this isn’t happening, there’s something wrong with the filters or the membrane.


Maintain your RO system by replacing the filters at the recommended time. High TDS is usually due to clogged filters or a damaged membrane.

6. Carbon dioxide concentration elevated

Carbon dioxide dissolves in the water and, depending on its concentration, increases or decreases the pH level of the water.

High amounts of carbon dioxide make the water acidic and result in increased pH levels which gives it a bitter flavor.


Ideally, our drinking water pH levels must always be between 6.5 to 7.5. If the RO water continues to be too acidic and bitter tasting, an alkaline filter can be fitted to further eliminate any pH level imbalances.

7. Storage containers leaching chemicals into water

If you store your RO water in plastic bottles then there’s a possibility that the bitter flavor might not be the system’s fault.

When water is stored in regular plastic bottles for a long time, not only does it develop a weird taste but also a bad odor.


Store RO water in food-grade plastic bottles or stainless-steel bottles. It also must be noted that plastic bottles have to be discarded after 3 months of storage or use.

Frequently Asked Questions

Q) What should reverse osmosis water taste like?

An RO system provides pure and clean water, with no contaminants, minerals, or trace elements. The RO water should be tasteless, colorless, and odorless. The reason it tastes so different is because of the dramatic reduction in Totally Dissolved Solids (TDS).

Q) How often should we change the membrane of the RO filter?

Bad-tasting RO water is usually a sign that the membrane has reached its last legs. This is why it is best to replace an RO membrane once every 2 years. If the volume of water usage is less than average, the membrane can be replaced once in 3 years.

Q) Is it harmful to drink bitter reverse osmosis water?

A bitter metallic taste in RO water is an indication that the water isn’t being purified completely and/or has a low pH level. Consuming this water can be dangerous for health and the issue must be addressed immediately. Additionally, bitter water prevents people from drinking frequently, leading to dehydration.

Final Thoughts

If your RO water tastes bitter the first thing you should do is conduct a water test. This might tell you a lot about why this might be the case. If the bitterness persists and you have already checked all possible causes, listed above, it is best to contact the manufacturer or consult with a water treatment expert.

Bitter-tasting water isn’t just unpleasant to consume but can also pose a health risk. The sooner a solution is found the better.

Chief Guru

Richard Boch is a chemical engineer responsible for designing water filtration systems for industrial and residential customers. He has more than 20 years of experience with ion exchange, activated carbon, and reverse osmosis. Richard's expertise has made him a go-to source for municipalities and businesses looking to improve their water quality. When he's not working, Richard enjoys spending time with his wife and two young children. You can also follow him on LinkedIn, Twitter and Facebook.

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