Is Reverse Osmosis Water Good for Cats? A Definitive Answer

Is Reverse Osmosis Water Good for Cats? A Definitive Answer

If you’re a cat owner, then you want to make sure your kitty is getting the best possible water. In this blog post, we’ll discuss whether reverse osmosis water is good for cats.

Reverse osmosis treated water is safe for your cat. RO removes heavy metals, disinfection byproducts, radioactive elements, and many other contaminants that can make your cat sick. Veterinarians and researchers are almost unanimous in their assertion that reverse osmosis water is safe and healthy for cats.

Reverse osmosis water is often thought to be healthier than regular tap water – but is that true for our feline friends? Keep reading to find out.

What Is Reverse Osmosisreverse osmosis filter for chlorine removal

Reverse osmosis is a water treatment method that removes contaminants from water by passing it through a semipermeable membrane. This process is often used to purify drinking water, as it can remove impurities like lead, fluoride, and chlorine.

How reverse osmosis works

Reverse osmosis (RO) is a water purification technology that uses a semipermeable membrane to remove impurities from water. The holes in the membrane, called pores, are very small. When pressure is applied, water can pass through the membrane. The contaminants, which are larger than the pore size, are left behind. The clean water is then collected on the other side of the membrane.

RO systems have a particle filter and an activated carbon filter to pre-treat the water. The particle filter removes any sediment or dirt from the water, while the activated carbon filter removes any chlorine. These additional filters protect the RO membrane and also remove some of the contaminants in the water.

A reverse osmosis system can be sized to treat all of the water in your house or just the water your drink and cook with. If the RO filter treats everything, it is known as a whole-house or a point-of-entry system. This size is very expensive, but it ensures that all of the water in your home is treated.

You can also install a RO filter under your sink to treat the water that comes out of your faucet. Smaller systems like this, known as point-of-use filters, are very common. They remove contaminants from the water that comes out of your faucet. This is much more economical than a whole-house system.

Read my articles on whole house RO systems and under-sink reverse osmosis filters.

Contaminants removed by reverse osmosis

Reverse osmosis is a great way to get rid of all sorts contaminants in your drinking water. It can remove chlorine, disinfection byproducts and fluoride, while also filtering out pesticidesPFAS (per- AND polyfluoroalkyl substances), pharmaceuticals, as well as arsenic.

RO is especially good at removing dissolved solids like chromium, copper, and lead.

The following table lists the removal efficiency for some of the contaminants that RO can remove from drinking water.

Contaminant Removal Rate
Aluminum 93-98%
Arsenic + 3 70-80%
Arsenic + 5 94-99%
Barium 93-98%
Bicarbonate 90-95%
Boron 55-60%
Cadmium 93-98%
Calcium 93-98%
Chloride 90-95%
Chromate 90-95%
Chromium-3 94-99%
Chromium-6 94-99%
Copper 94-99%
Cyanide 90-95%
Fluoride 90-97%
Iron 2 93-98%
Lead 94-99%
Magnesium 93-98%
Manganese 2 93-98%
Mercury 93-98%
Nickel 93-98%
Nitrate3 85-90%
Phosphate 93-98%
Potassium 90-95%
Radioactivity 93-98%
Selenium 93-98%
Silver 93-98%
Sodium 90-95%
Strontium 93-98%
Sulfate 93-98%
Zinc 93-98%

There are many more contaminants that reverse osmosis can remove.

Can Cats Drink Reverse Osmosis Water?Cat drinking RO water

If you own a cat, naturally you want to give them the best water to drink. Many people give their cats the same water that they drink. Many people think that if the water is good enough for them, then it must be fine for their cats as well.

Although this makes sense, it’s important to keep in mind that cats are not people. Some foods that people eat, such as onions and garlic, aren’t safe for cats.

So, the question remains – is reverse osmosis water good for your cat?

Is RO water safe for cats?

You’ve probably heard that reverse osmosis water is the highest quality and safest drinking water. But is RO-treated water safe for cats?

Yes, reverse osmosis water is safe for cats to consume. In fact, reverse osmosis water is probably the best type of water you could give them.

Why? Because reverse osmosis removes a long list of contaminants that might be in your drinking water. By treating the water you give to your cat, you are providing H2O that is both toxin-free and contains no harmful chemicals.

Need more evidence?

The Max Planck Animal Resource Center uses reverse osmosis treated water at their state-of-the-art animal facility. They explain that RO-treated water is the safest and best water for all animals.

Should I give my cat reverse osmosis water?

If you drink tap water, then it likely contains chlorine or chloramine to disinfect it. These disinfectants can cause gastrointestinal problems with your cat. Reverse osmosis can remove these disinfectants.

Another issue with chlorinated water is the formation of disinfection byproducts – these are chemicals that form when chlorine reacts with organic matter in the water. These byproducts can be harmful to cats.

Fortunately, reverse osmosis filters remove up to 99% of these compounds, making the water much safer for your cat to drink.

Concerns over minerals

Reverse osmosis systems remove the minerals that are in your water. Many people worry about their pets not getting enough of these essential compounds if they’re not drinking it.

However, vets tell me cats get all the vitamins and minerals they need from what they eat – just like humans do.

In addition, the amount of minerals in water is considerably lower than what cats need on a daily basis. Cats can’t get all of the essential minerals they just from drinking water. Where do they get them? From the food they eat.

I checked the nutritional information on 5 popular brands of canned cat food to see how much of each essential mineral they provide. It was difficult to get this data because there are no federal reporting regulations for cat food like there are for human food. Some brands report the amount of every mineral. Others only reported 1 or 2.

The table below summarizes the daily recommended allowance for essential minerals that a 9-pound adult cat should eat. It also contains the amount of each mineral found in canned cat foods.

Mineral Daily Recommended Allowance Amount in Cat Food
calcium 180 mg 171 – 310 mg
magnesium 25 mg 100 – 212 mg
iron 5 mg 17 – 250 mg
phosphorus 160 mg 142 – 456 mg
potassium 330 mg 380 – 789 mg
zinc 4.6 mg 14 – 28 mg

As you can see, if you feed your cat just one can each day, they will get all of the essential minerals they need for a healthy diet. You don’t need to worry about your reverse osmosis system removing these minerals from your cat’s water.

Add a remineralizer to your RO system

But, if you’re worried about giving your cat water that doesn’t have essential minerals like calcium and magnesium, you can add a remineralizer to your RO system. A remineralizer adds back these minerals – this also improves the taste for you!

Read my article on how to re-mineralize your water.

What Type of Water Should My Cat Drink

Cats need plenty of clean, pure water every day. Water is essential for their health and wellbeing. It cushions their joints, gives their coats a healthy sheen, and maintains health digestion.

Just like people, cats need clean and safe water. Your feline’s drinking water must not contain any of the following contaminants:

  • microorganisms: Bacteria, viruses, and parasites cause disease and illness.
  • organic chemicals: VOCs, solvents, pesticides and other man-made chemicals cause cancer, organ damage, and other health problems.
  • radioactive elements: Much of the drinking water in the US contains radioactive elements such as radium and uranium. The EPA considers these substances to be carcinogenic.
  • heavy metals: Compounds such as lead, chromium, and arsenic can make your cat sick.

Risks of drinking unfiltered tap water for your catCat drinking tap water

In most cases, it is okay for people to drink water from the tap. Similarly, it is safe for your cat to drink tap water, too. Veterinarians agree that tap water is safe for cats.

However, while tap water may be a viable option, there are several drawbacks to consider.

  1. Chlorine. Disinfectants can cause gastrointestinal problems in some cats. While this isn’t life threatening, it may cause your cat to drink less water, which is a risk factor for kidney issues.
  2. Disinfection byproducts. Water that has been chlorinated may contain byproducts of the disinfection process. These chemicals, called trihalomethanes, have been linked to cancer. Reverse osmosis is very effective at removing THMs and other byproducts of disinfection.
  3. Fluoride. Some municipalities add fluoride to their water supply. While fluoride is considered safe for humans, many people are concerned about consuming it. Reverse osmosis removes fluoride from water.
  4. Contaminants. In some areas, public water has concentrations of contaminants that are a health concern. This is not typical, and most of the levels of these compounds are below drinking water standards. However, PFAS – the so-called forever chemicals, have been found to be in many public water supplies.

All in all, do you want your cat drinking water that isn’t pure and clean?

Should my cat drink well water?

If your household gets water from a well, you are the one responsible for ensuring its quality. Unlike public water supplies, the EPA does not regulate private drinking water wells.

Did you know that your well water may contain harmful bacteria, viruses, and parasites? It could also have high levels of metals or chemicals. You can test your well water to verify that it is safe for your cat – and your family – to drink.

If your drinking water well is “clean” and you want to give it to your cat, then that’s perfectly fine. It is also OK to drink it yourself.

Can I give my cat bottled water?Bottled water for cats

Many people give their cats bottled water – especially when they’re traveling or at work.

Bottled water, while a safe option, is not the most environmentally friendly or economical choice.

I prefer using a refillable water bottle that I fill with filtered water from my house. This ensures your cat is getting clean, pure water. It also helps to reduce plastic waste.

One thing many people may not realize is that most bottled water is just tap water that has been treated using reverse osmosis. Read my article on reverse osmosis treated bottled water.

Benefits of reverse osmosis water for cats

All of the pollutants mentioned in this post can be effectively reduced using reverse osmosis systems. If you want to make sure your cat is drinking the cleanest possible water, then an RO system is a great investment.

Some benefits of giving your cat RO treated water are:

  • No pollutants
  • No chemical odor or taste
  • Reduced microbial count

Under-sink reverse osmosis filter

Here is the under-sink reverse osmosis filter I installed in my kitchen. You may interested in something similar for your home.

Check Pricing on Amazon


Is it safe to use a carbon filter for my cat’s water?

Carbon filtered water is safe for cats and other pets. Activated carbon filters are an effective way to remove chlorine, VOCs, disinfection byproducts, and other toxins from drinking water.

Is soft water good for my cat?

Water softeners use ion exchange to remove hardness (calcium and magnesium) from drinking water. Unfortunately, cats need these minerals for good overall health. Cats, and people too, get the minerals they need from their food and not the water they drink. Soft water is safe for your cat.

Is reverse osmosis water good for my other pets?

Reverse osmosis water is safe for all pets. It is the best way to ensure your pet is drinking clean, pure water.


Reverse osmosis water is the best choice for your cat – and all of your pets. It is safe, clean, and pure. RO systems are designed to remove contaminants from water, leaving you with healthy drinking water for your family – including your furry friends!

Reverse osmosis removes more contaminants than any other filtration method and leaves behind a high-quality product that is perfect for your pup. Not only will they be getting clean, fresh water, but you’ll also be doing your part to keep them healthy and hydrated.

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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