Updated 12/3/22.

Everyone is familiar with the 3 basic nutrient categories: protein, fat and carbohydrate. But there’s a 4th nutrient that’s just as important (if not more!), yet it is usually overlooked by most guardians and even veterinarians—water! You may know that two-thirds of an animal’s body is water, but in molecular terms, the body actually comprises more than 99% water molecules!

The kind of water your cat drinks can have a major impact on her health, because all water is not created equal. The basic types are: municipal tap water, well water, distilled water, and spring water. (Any water source can be filtered to make it healthier for your cat.)

Cats in sink

Flynn, Puzzle, and Mitty waiting for me to perform the magic trick that makes the water flow. Good thing one of us has opposable thumbs!

I realized the power of water years ago when I had to go out of town for a few days. One of my cats, who had Addison’s disease, stayed at the clinic while I was gone. He ate only the raw diet I provided, but he drank Denver tap water there, which he never did at home—we had a faucet-mounted filter. Marcus developed severe vomiting and diarrhea while at the clinic, both of which cleared up immediately when I got him home and back on his own clean water. Since then, I have noticed many significant health improvements when cats stop drinking tap water.

The quality of tap water varies tremendously from one municipality to another. Denver is far better than most, since there is no upstream agricultural land–but it’s still not great. Municipal water generally contains chlorine by-products, fluoride, and harmful contaminants such as bacteria, arsenic, chemical runoff, toxic herbicide and pesticide residue, heavy metals, rocket fuel… or even radioactivity, as cities downstream from military or nuclear facilities may contain. Some cities’ water tastes bad; but taste is not a reliable indicator of what’s really in there. In fact, some of the yuckier tasting waters are among the cleaner ones.

From a more holistic perspective, the late Dr. Masaru Emoto of Japan developed a technique for photographing water crystals that clearly demonstrates the poor quality—perhaps even danger—of water from many major cities. His book, Hidden Messages in Water, contains many photos showing this, and much more. (For more on Dr. Emoto’s work, which was featured in the movie “What the Bleep Do We Know?” visit Dr. Emoto’s official website.)

If you must use tap water, filter it before your cat can safely drink it. Even a simple Brita filter will remove chlorine, lead, arsenic, bacteria, and some chemicals. Faucet-mount filters are a step up; under-sink or whole-house filters are best. There are many brands and a huge variation in price, but in general, you do get what you pay for. There is lots of info on the Internet about which filters do what. If your city water is seriously nasty, get the best filter you can afford. A reverse osmosis system is the most thorough, but minerals must be added back to the filtered water. My personal favorite is the Berkey, which comes in several sizes, and offers filters that even remove fluoride.

Well water is sometimes wonderful, sometimes really bad. The only way to be sure is to have the water tested. Again, filtration may be the best option if you are on well water.

Distilled water has been purified so that it does not contain any particles at all. While  purity may sound good, you really should not use distilled water for drinking. The reason lies in the fundamental nature of water. Water and solutes (molecules and particles) move by osmosis and diffusion, respectively. You might remember these from high school chemistry class! Basically, water moves by osmosis from where there is more of it, to where there is less of it; and solutes diffuse from an area of high concentration to an area of low concentration. Distilled water contains zero solutes, so when it enters the intestines, diffusion will actually pull solutes out of the body. Drinking only distilled water can ultimately cause deficiencies in sodium, potassium, and important trace minerals. Distilled water also becomes acidic when exposed to air. It may contain higher levels of volatile compounds such as benzenes, trihalomethanes, and trichloroethylene, as well as highly toxic “disinfection by-products.”  In people, exclusive consumption of distilled water is associated with high blood pressure and heart arrhythmias. While distilled water can be valuable when used for a short-term process of detoxification, it’s not safe for long-term consumption.

Spring water, if it’s really from a natural spring, and if the spring itself is good quality, is the best choice for cats (and the rest of the family, too!). According to an NRDC report, 25% of bottled water is simply bottled tap water that may or may not have been further treated. Generic and grocery store brands should be avoided; many of them tested positive for bacteria and chemical contaminants. Designer imports Perrier and Evian tested relatively clean. Calistoga is a natural spring in northern California; most of its samples were okay. Arrowhead Springs is a real spring just outside San Bernardino; but based on test results–and having personally seen the condition of the open pond from which the water is pumped–I’d recommend avoiding it. .

To get your cat to drink more water, try a pet fountain. The best one we’ve ever found is Glacier Point Cat Fountain, which is made of high quality ceramic instead of plastic. This excellent fountain doesn’t have those annoying nooks and crannies that are so hard to clean; it keeps the water cool; and it doesn’t leach harmful chemicals such as BPA into the water like plastic fountains do. It’s a great investment that will last a lifetime.

The bottom line is that you can provide the best food and great supplements for your cat, but if the water is poor quality, optimal health will remain out of reach. Pure, good quality water is an essential ingredient of your cat’s wellness program!