Should cats drink purified water?

Common sense informs me that in an ideal world the best water for cats is free of all harmful substances. This means that, in theory, it is neither tap water nor bottle water nor softened water. In short, purified water is possibly better for your cat than any other water but tap water sustains most humans and is safe to drink in the USA because of the regulations in place by the US Environmental Protection Agency with respect to public drinking water under the Safe Drinking Water Act. If tap water is safe for people it is obviously safe for cats. It is a question of quality at the end of the day and although tap water is of very good quality it is not of the very best quality.

But the important point to make is that tap water is good enough for domestic cats and this is a complex topic. There are complications with purification systems. And there is nothing in the cat health literature that I have at my disposal which tells me that cat owners should dispense with using tap water. There are no recommendations by veterinarians, to the best of my knowledge, that cat owners should use purified water and not use tap water. Purification systems are installed at home and they may go wrong and they may inject into the water substances which a cat owner may not be aware of and which may harm their cat. Plus they are expensive.

Below I also discuss briefly reverse-osmosis purification systems, bottle water, soft water and tapwater.

Associated: How much water do cats need daily?

Reverse-osmosis Purifiers

People also ask whether “reverse-osmosis water is good for cats”. Reverse-osmosis water is purified water. It removes the large majority of contaminants from water. It removes up to 99%+ of ions, particles, bacteria and pyrogens from the water. My first impression is that reverse-osmosis water is good for cats because it purifies the water. However, my earlier research on this subject is that this water could be described as “superclean” and although it sounds fantastic it is no good for cats. Water produced by reverse-osmosis has been described as “hungry water” or “death water”. It contains positive ions and not negative ions and is acidic rather than alkaline (a higher pH). Therefore, I do not think that reverse-osmosis water is good for cats.

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Bottled Water

The ironic aspect of bottled water is that a lot of people drink it instead of tap water but studies indicate that bisphenol A (BPA), a substance in plastics, is linked to hormone disruption. The thyroid gland produces thyroxine, a hormone. We are told that the BPA molecule is similar to the thyroxine molecule.

When I studied this subject many years ago, I said that bottled water is a product of marketing over substance. Studies indicated that 30% of bottled water has some chemical contamination such as neurotoxins and carcinogens in it (styrene, toluene and xylene). Antimony used in the manufacture of the plastic leaches out into the water especially when it is warm.

The point being made is that there is some doubt about the safety of bottled water and that being the case it can’t be said to be better than tapwater which is certified to be safe for humans. This removes bottle water from this discussion.

Associated: Do cats prefer cold water?

Tap Water

Tap water in the USA as we know is obviously drinkable but is not an ideal and the objective of this article is to find the best water for cats. There is chlorine and fluoride in tap water. On balance chlorine is beneficial it is said but some people disagree. It kills bacteria. But it reacts with other substances to form toxins. Fluoride, as you know, helps prevent tooth decay. I’m told that 70% of people use fluorinated water in the USA. Potentially and probably actually there are also dioxins, inorganic poisons, parasites, pathogens, viruses and fungi in tapwater. Purifiers remove these unwanted items.

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Energized Water

What is energized, alkaline and toxin-free water? it is claimed to be the best water for cats. It can be produced at home using a machine called an alkaline ionizer. The water is a powerful antioxidant. However, these machines sell for US$1,795 (as at several years ago). I’m sure the price varies but that is the price I obtained online. An advantage of these machines is that they produce alkaline water and disease thrives in an acidic environment.

However, there is another caveat which is that drinking alkaline water may not be all that it is cracked up to be. There appear to be inherent dangers. One expert online says that the ideal water to drink has a pH range of 7.4 to 7.6. This is very neutral in alkalinity or acidity. In addition, alkaline ionizers do not adequately filter water. Further, if the tap water contains metals they will be concentrated in alkaline water which may be 2 to 3 times higher than the levels found in untreated tap water. There are probably other issues which I will let you research online. I would not recommend this water for cats.

Associated: Water fountains for cats.

Soft Water

There is a big question mark about soft water. My distinct impression is that cat should not drink softened water. I have written on the subject in full so I won’t go over it again here. In short, an ion-exchange water softener uses salt and results in an increase in sodium in the water and salt in excess in water is not good for cats. If you can add some further information to that it would help me tremendously.

Note: there is a connection between hard water and urinary tract crystals. Another complication.


To return to the question in the title, “should cats drink purified water?” I believe that the answer is that there is no requirement or pressing need for domestic cats to drink purified water so you cannot say that they should drink it bearing in mind the complications described on this page.

Rain Water

Although purifiers remove unwanted substances and organisms, it is my experience that sometimes cats like to drink water out of puddles in the back garden or where rainwater lies on the ground. It is natural water from the heavens. It may not be a good idea to remove all organisms from water as it may make it unnatural. Exposure to certain organisms and pathogens may help boost the cat’s immune system. Superclean water is unnatural.

Perhaps the best water for a cat is rainwater from a water butt. However, you cannot presume that it is safe to drink because it might not be collected properly. And the rain might pick up contaminants in the air if the air is polluted. And if it comes off a roof the water might pick up substances from the roof which are hazardous to a domestic cat.

If rain water is captured in stainless steel buckets or glass containers and poured through a filter system of some sort it is arguably the best water for cats to drink because it is the most natural.

This is a complex subject. I welcome the input of others.

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Michael Broad

Hi, I'm a 74-year-old retired solicitor (attorney in the US). Before qualifying I worked in many jobs including professional photography. I love nature, cats and all animals. I am concerned about their welfare. If you want to read more click here.

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4 Responses

  1. M E King says:

    Thank you Micheal without blogs like this on the internet it would be hard to find good information on cat care. The subject of water came up at our house a few weeks ago when my hubby bought some distilled water by mistake.

  2. M E King says:

    We do not drink our well water it is simply too hard. Our cats drink purified water and the well water. They have 24/7 access to both and often migrate between one of the other. We are more concerned about what holds the water. I use high quality stainless and no plastic or ceramic. Often I leave the tub tap dripping slightly and that is their absolute favorite place to drink. They had a fountain but the Tabbinese Tigers kept taking it apart.

    • Michael Broad says:

      Nice comment ME. You are a very concerned, enlightened cat guardian. I hope you, your family and your cats are well.

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