In Hot Water
on the dangers of and alternatives to

January 2013

Beware of the pool.

The B-52's, "Private Idaho"


I'm sitting on the dock behind my brother's house in South Beach. My father, knowing my habits, comes out and says "don't go swimming out there. You have no idea what's in the water." He asks me why I don't join my nephew, pictured above, in the pool. The problem is, I KNOW what's in the pool.

What I'm about to tell you has not been evaluated by the FDA. I am not licensed to tell you what will or will not cause disease. That said, consider that heart disease is the #1 cause of death in the United States. Many if not most cases of heart disease can be prevented through lifestyle changes. After all, heart disease was virtually unknown before 1900. It hasn't skyrocketed because we live longer, nor just because infectious diseases have been suppressed (source). It's certainly not due to saturated fat. And the main problem may not be trans fat either. There's one thing that we consume a whole lot more of, and that's water. Don't worry about cholesterol; worry about chlorination.

Chlorine is extremely reactive. That's why it's so effective as both bleach and as a disinfectant, i.e., poison. And if it's going to kill things by reacting with organic compounds, it's certainly going to react with your organs. That's why drinking chlorinated water is such a problem. There have been very few studies on relationship between tap water chlorination and heart disease, but for those that have been done, see here.

Worse than putting chlorinated water into you is putting yourself into it. For one, there's usually more chlorine in a spa or swimming pool than in tap water: specifically, 3 parts per million vs. 0.5-2 parts per million, respectively. For comparison, .2 ppm will quickly kill most fish. This brings to mind the tagline from Jaws: "don't go in the water."

Unfortunately, like breathing sidestream smoke, hanging out by the pool isn't much better. Chlorine is highly volatile, and most indoor spas and swimming pools are poorly ventilated, especially in the winter. The same goes for the shower. How many of us bathe with the fan on and the door wide open? Consider that just by breathing the steam coming off a tap water shower, you absorb six to one hundred times more chlorine than if you drank the water. You might want to be less bashful. That's more chlorine from one shower than from a week of chlorinated tap water. And how many hot showers do you take a week?

For all these reasons, I recommend sink and shower water filters, and if you use a dishwasher, a whole-house filter. For drinking water filters, I've used New Hampshire-based Lakota Scientific, run by environmental activist Barry Hanson. The best shower filter, at least according to this chart, is the VitaShower, although their current model has gotten a number of poor user reviews.


This odious detritus is not just nasty; it's unnatural. You may have heard not to mix bleach and ammonia (which is what stale urine turns into) because it creates a poisonous gas. That gas, a chloramine related to chloroform, an anaesthetic abandoned after it killed enough people, is a type of organochlorine. This class of compounds includes the most toxic substances known. The worst of these is TCDD, a.k.a., dioxin. Chlorination does not create dioxin, but war machines do. In 1952, Monsanto let the US government know that their Agent Orange contained dioxin. Ten years later, and over the next ten years, 20 million gallons of Agent Orange was sprayed over Vietnam. The destruction of the World Trade Center released nearly six times the highest concentration of dioxin ever recorded.


Whether for health reasons or just to avoid discomfort, people seek alternatives to chlorinated pools. Some facilities advertise "saltwater" pools. I've had to spoil many a friend's fantasy by telling them that saltwater pools are not, in fact, chlorine-free. Do you remember the formula for salt? Sodium chloride. As we all know, salt dissolves in water. It dissolves because it separates into sodium and chloride. The chlorine liquid or tablets commonly used in conventional chlorination are the same thing saltwater pool systems generate from salt.

Why isn't the ocean chlorinated? Because chloride ions are not the same as chlorine gas. It takes electricity to make the latter, which doesn't naturally occur in appreciable amounts because it so highly reactive. That's why, in 1989, five men dumped fifty pounds of chlorine pellets into the Atlantic ocean so they could go swimming. I would have used jumper cables.

The chlorine level in a saltwater pools is kept at 2-3 ppm. This is the same amount as is recommended for a regular pool. Why then do saltwater pools smell less and feel better? It's not, as some would have you believe, because the chlorine in public pools is kept at higher levels. It's because in conventional pools, the chlorine level often falls too low. For good basic info on pool chlorination, see "Chlorine Chemistry" or "Pool Treatment 101," and for a detailed explanation, see "Chlorine, Stainless Steel Tanks, and Corrosion" here. Finally, there's the PoolSpaForum.



Apparently, with saltwater treatment, chlorine levels are more easily maintained at sufficient levels to prevent chloramine formation. There are other advantages to saltwater filtration as well: the pH is kept near neutral and the water is softer (less calcium). However, the same additional chemicals that are usually incorporated into chlorine tablets may still need to be added separately. In the commentary to "What are the advantages and disadvantages of a saltwater swimming pool?," there is some debate about this.

In conclusion, 2-3 ppm free chlorine in a pool, even a saltwater one, is an unacceptable level for me. One reader asks, "if I have arthritis and the only way they I can get aerobic exercise and maintain healthy range of motion is water aerobics or water therapy, is the risk of swimming in organochlorines worse than frozen joints or obesity? Is there a relatively "safe" exposure?" That goes beyond the scope of this article, but before I talk about other sanitation options, I would ask a similar question:

How much sanitation is really necessary? Where's the proper balance between exposure to germs and exposure to toxins? Keep in mind that at public facilities, liability is a major issue, and if you're a hotel or athletic club, protecting yourself from a lawsuit "is not always about doing the right thing, but rather about doing the typical thing." Sadly, what's typical in this age of antibacterial soap, is pathological biophobia. One time I was taking a group of inner city youth seining. It means wading into a pond to see what you can catch with a big net. One child refused to leave the shore. "I ain't goin' in there," he declared. "There be allergy in there!!"

Here is a list of sanitation options. One popular alternative to chlorine is bromine. For most people, it doesn't cause the same symptoms (bad smell, dry skin, red eyes, etc). But don't judge a pool by its odor. Contrary to popular belief, bromine, with just as many "disinfection byproducts" as chlorine, can be just as problematic. For one, it interferes with thyroid function. Ozone or UV treatment systems are far healthier but can run in the thousands.

Andrew Weil recommends copper-based Cleanwater Blue, but it still requires other chemicals. The Floatron (besides having a more entertaining name) is also copper-based yet the manufacturer claims that it doesn't require any other chemicals besides an occasional "shock," typically with chlorine (see "Routine" here). I wonder if you even need the $250 Floatron unit. Judging from the patent for it and this this evaluation, it generates copper ions the same way saltwater systems generate chlorine, namely, through electrolysis. When I was about 11, I built an electrolysis machine for a science project for about $5. These $4,000-20,000 industrial systems may be no different. You could probably make your own colloidal silver and use it the same way, although copper is surely cheaper. Besides, If you're going to play DIY I would get some knowledgeable guidance. Otherwise, you might turn blue. That's the color of larger, clumping particles of colloidal silver, as you can see at minute 2:20 here.

An enzyme-based product worth looking into is Eco One. Here's one professional's instructions for using it. But I have friend who has been maintaning his homemade hot tub quite easily with nothing but hydrogen peroxide. Whereas chlorine takes hours to dissipate, peroxide breaks down into oxygen and water in minutes. And if, like my friend, you are blessed with plenty of clean water (e.g., a gravity-fed spring) and a cheap source of heat (he burns pallets in a Chofu), you can use less peroxide and just change the water as needed.

The peroxide in question is 27% or 35% strength, not the 3% peroxide sold in drug stores. The amount to use is whatever will achieve at least 50 ppm. It would be difficult to use too much: 3% peroxide is 30,000 ppm. The proper level is typically achieved with 1/4 to 1/2 cup per 100 gallons weekly, depending on frequency of use and how clean the water is kept (see delectable detritus list above). It helps to shower before you get in and to put another 1/8 cup in after you're done. If your water is mineral-rich, then unless it's pre-treated, it will require larger amounts of peroxide, but for a hot tub, this is not a big deal. I don't know further details, including whether peroxide alone will prevent algae (or allergy, for that matter).

Perhaps the oldest and simplest method of water purification is boiling. Pasteurization works at least as well as filtration, chlorine, or UV for bacteria and is more effective against protozoa, worms, and cysts. You can't heat enough water on your stove for your spa or pool, but the sun can! This system is easy to install, runs automatically, and has negligible maintenance costs. Designed "to be used where conventional water treatment is not available or is unreliable" (see sample installations in Samoa, Cambodia, and Tanzania here), it sells for about $2,000 and has a life expectancy at least 15 years. That's more than most $20,000 cars. Poor third-world countries can't afford Chyslers or chlorine!

This particular model can treat 264 gallons a day (a sunny day, that is), so it can treat the average 400-500 gallon hot tub in two days, which may be enough depending on use. And did I mention that it will heat your spa as well? The average swimming pool has about 17,000 gallons in it, which would take about two months. But someone could easily build a larger model, one that sits on your roof. After all, it's just a solar water heater (detailed instructions here).

All of the above "purification" systems only "sanitize" the water. They kill stuff. They don't remove contaminants. That's typically done with filtration. But one thing that does both, and it's the oldest and most effective water purification system on earth, is distillation. That's what happens when seawater evaporates and comes back down as freshwater, i.e., rain. It may or may not be healthy to drink distilled water, but I assume it's safe to bathe in; after all, this site says Einstein and three out of four signers of the Constitution agree!

The above solar pasteurizer raises the water temperature to 175ºF. A machine that raises it above 212º, water's boiling point, is called a "solar still." Stills are used to make alcohol because it is a volatile organic compound (VOC): it evaporates sooner than water. Similarly, some contaminants are also VOCs: they evaporate with the water. But this is easily remedied with gas vents, i.e., tiny holes in the return pipe that allow the VOCs to dissipate after the distilled water condenses but before it cools down. You can also use "fractional columns" or an activated carbon filter.

To evaporate an entire swimming pool of water is very energy intensive, but the sun is free. The question is the rate of filtration vs. the rate of contamination. If people get the pool dirty faster than you can clean it, you have a problem. Again, it may just be a matter of building a bigger system. I couldn't find any online, so there may be a major problem with the concept. One problem I did come across is that the gunk (i.e., scale deposits) that are left behind can be hard to clean up. Here is a patent for an industrial distillation treatment system. Let me know what it says!

For now, since I live in Asheville but I'm from Miami, when winter comes, I just go visit family for a couple months -- and swim when my dad's not looking (shark attacks are extremely rare). The rest of the time, I just throw in the towel (let it get bleached instead of me) and stick with walking. When summer returns, I go jump in a lake. Unfortunately, chemical run off from paper mills, other industries, and home use of chlorinated detergents combined with high natural levels of organic matter have rendered many lakes and even rivers unsafe as well. Basically, you can't escape the world we've poisoned by trying to "clean" it. Better to focus on saving future generations instead. Don't throw the baby out with the bathwater!