Archive for June, 2011

Chlorine Generators (salt systems)

It can be complicated deciding which pool is best for your family. Many questions revolve around salt-water pools or chlorine free pools. Salt-water pools are NOT chlorine free pools. A salt-water pool is simply one that utilizes a chlorine generator. Chlorine generators have been around for decades. As technology and materials continue to evolve, chlorine generators continue to improve in performance.

Why Salt-Water?

Ocean water has a salt content of around 35,000 parts per million (“ppm”). Humans have a salt taste threshold of around 3,500 ppm. Most chlorine generators require a salt content of 2500 – 6000 ppm in the pool. A unit that needs less than 3500 ppm to operate effectively is optimal. If the salt content is higher, that warm, salty water will be pretty distasteful!

Swimming in a mild saline solution is much like taking a shower in soft water. Generally, when people swim in a non-chlorine generator pool (a pool with no salt water in it) they feel like their skin dries quicker upon exiting the pool. They may feel and/or see a whitish residual, chlorine flaking, on the skin. In a salt-water pool (one with a chlorine generator) the water feels smooth, your skin feels smooth and many people feel more refreshed.

What Does a Chlorine Generator Do?

A chlorine generator’s main function is to produce chlorine for the pool so you do not have to buy it, store it or handle it. These are big advantages for many pool owners. Chlorine generators, when functioning correctly, produce chlorine constantly (when the pump is running) with most units. This keeps a residual of chlorine in the pool that prevents algae from growing. The secret is keeping the cell free of calcium and mineral deposits–the cell itself is made up of precious metals-it must be maintained so it can continue to make chlorine.

Through the process of electrolysis, water passing over the chlorine generator cell produces chlorine that is instantaneously transformed into Hypochlorous acid. When any type of chlorine is added to water it ALL makes the SAME thing: Hypochlorous acid. It does not matter if it is Sodium Hypochlorite (liquid chlorine), Tri-chlor and Di-chlor or Lithium based, Cal-hypo or even gas chlorine–it all makes Hypochlorous acid. Hypochlorous acid is the active sanitizer; this is what kills algae and other harmful stuff in the water. Its effectiveness is totally predicated on balanced water conditions and, more importantly, proper pH. So, with a salt water system or chlorine generator, you still must maintain your water balance (pool chemistry) properly. As long as you do this, a chlorine generator is a good choice.

On the previous pagewe introduced the concept of building salt-water pools using chlorine generators. Here is some additional information for consideration when selecting a chlorine generator for your swimming pool.

Types of Chlorine Generators

There are two types of chlorine generators in use today on residential pools. The first one is a brine unit. This unit does not require the pool to have salt added to it. A tank or chamber at the pool equipment area has a predetermined amount of salt in it. Through electrolysis, chlorine is produced and immediately injected into the pool circulation system. These units are messy and produce by-products that are not simple to dispose of. These are the less common of the two types.

The recommended unit is the type requiring that salt be added to the pool. There are two types of these units. One has the chlorine-producing cell and the electronics installed at the equipment while the other has the cell installed in the deck near the pool with the electronics usually located at the equipment. The deck unit works on the principle of convection. It makes chlorine even if the pump is off while the other more common unit makes chlorine as water is passed through the cell with the circulation system (pool pump on.) In both cases the cell must remain free of mineral deposits or it will not work properly. Of these two units, the inline unit with 24-hour circulation is the preferred choice. (Did you know that every commercial swimming pool in the United States requires 24-hour circulation?)

What About Polarity?

There are non-reverse polarity units and reverse polarity units. A reverse polarity unit reverses the electron flow through the cell causing mineral deposits to flake off. In some instances the now larger particles will get caught in the filtration system. So the claim that the units help keep calcium scum off the tile is partially correct. These cells do not require as much cleaning. (Don’t believe a claim that a unit doesn’t ever need to be cleaned.) A reverse polarity unit will cost nominally more than a non-reverse unit.

Bottom Line

Chlorine generators can help fight against waterline scum build-up. They create a better, healthier swimming experience for most people. It isn’t necessary to handle or buy chlorine, and, if the unit is functioning correctly, chlorine residual will always be present in the pool, eliminating algae. This makes it nearly impossible to get burning red eyes from chloramines, which is usually the culprit. Even with a chlorine generator, you still must maintain your pool. You still must maintain correct water balance, and you must maintain the chlorine generator. The best pool will have 24/7 circulation, correct hydraulic design with an in-floor cleaning system for bottom up cleaning and circulation, a quality ozone system, and a chlorine generator for sanitizer residual. You can expect to pay at least $1,000, and up to several thousand dollars, for a quality chlorine generator unit.

DISCLAIMER: If you do not maintain a chlorine generator or maintain your pool chemistry you can destroy your pool’s interior finish, decking and pool equipment. Chlorine generators and salt-water pools are great but they need care.

You now have the recipe for a low maintenance pool. Enjoy, and swim safe!


  1. M. Hery*,
  2. G. Hecht*,
  3. J. M. Gerber*,
  4. J. C. Gender,
  5. G. Hubert* and
  6. J. Rebuffaud

+ Author Affiliations

  1. *Service Evaluation et Prévention du Risque Chimique, Laboratoire d’Etude Générale de I’Exposition Général, INRS Avenue de Bourgogne, Boite postale No. 27, 54501 Vandoeuvre-les-Nancy, France

  2. †Laboratoire Interrégional de Chimie de I’Ouest Nantes France

  3. ‡Laboratoire de Chimie de la CRAM de Normandie Rouen, France
  • Received December 16, 1994.


Specific sampling and analytical methods were developed to assess the concentration of chloramines in the atmosphere of indoor swimming pools because swimming instructors had complained of irritation (mainly eye and lung). The sampling method is based upon the reduction of chloramines to chlorides which are then analysed by ion chromatography. The chloramine concentration in the atmosphere of 13 swimming pools (including five recreational centres and one reeducation centre) was measured, showing that the concentrations were higher in the recreational centres. The influence of slides, bubbling baths, waves and other activities were demonstrated. A correlation was made between the level of pollutants and the complaints registered, leading to the proposal of a ‘comfort’ limit value.

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Swimming Pool Conversions

Becoming aware of the concept of natural swimming pools, it seemed to me swimming pool conversions were the next logical step. With some 4 million chlorine pools in the U.S alone, surely some pool owners would appreciate an ecological pool design.


Pool conversions gradually turned into my pet project. I set out to design a way to convert existing pools to natural filtration. Chlorine free with no chemicals of any kind. Maintaining crystal clear, fresh clean water.

It turns out that it may be fairly easy to attain. Well designed pool conversions should, along with natural swimming pools, easily meet municipal ‘drinking’ water standards. This with minimal change to the existing pool.

Adding a conversion may require a bit more elbow grease at first, but truly shouldn’t be much more work than the traditional chemical bath of a chlorine pool. A true chlorine alternative.

The building of pool conversions requires a basin equal to 5-10% of the pool by volume, and about 4ft deep.(1 cubic foot=7.48 gallons) Attached is a smaller basin up on the pool deck. This allows for getting around the pool as well as for excellent oxygenation.


Creating a sort of generic ‘flow form’.


Basins may be constructed of concrete, faux stone, adobe/stucco , stone mortared, or even wood.

Covering the pool with ‘Pebble Tech’ plastering will add to an overall more natural feel. You could even cover the basins.

I do like the idea of lining with a pond liner, otherwise. There will be less chance of mineral leaching in the water, plus a pond liner may go years longer without any maintenance. You never want to disturb a filter basin that is working properly. Cleaning out the filter basins with the up-flow filtration should be a rare occurrence.


Fill the basin with some sort of inert gravel, maybe half inch size, haydite, or clay beads. Haydite is especially good due to its incredible surface area for beneficial bacteria to adhere to. Bacteria that is required for biological filtration.

Some water gardeners cringe at the idea of using cinders due to what they’ve seen as a clogging problems. This may be because of large fish loads that the filter simply cannot keep up with, but cinders may also add minerals that you don’t want. So ultimately I can’t recommend using them.

Use a Jandy valve to divert 2/3rds of the water away from the existing plumbing to percolate up through the larger basin. From there the water pours out and down into the second smaller basin, and finally back to the pool.

Within the pool conversions larger basin grow a diversity of aquatic plants. Good choices are aquatic mint, for its antibacterial properties, and reeds. It is of course best to have plenty of diversity. Diversity being the strength of any ecosystem. All combined, the system will complete the nutrient cycle.

When deciding on placement of the filter be aware of the skimmer, a very important piece of the filtering process. Everything floats first and should be removed before they can break down. Good circulation within the pool is essential.

UV Sterilizers could be used for further polishing of the water. This depends on personal preference and tolerances.

Bacteria Culture or Microbe Lift may be used in the filter basin to ‘seed’ the bio-filter, adding diversity and to speed up the bio-filtering process.

There you have it; a naturally filtered swimming pool, with a two-tiered pool waterfall and beautiful water garden to boot. Pool into pond conversions offer a true chlorine alternative.No more chlorine poisoning, chlorine allergy, chlorine irritations or cancer risk. Pure chlorine free pool swimming.


*Scientific American – Chlorinated water exposure may boost cancer risk.

I would like to add, that after discussions with Dr. John Todd of Ocean Arks International and Michael Littlewood of Eco Design Scape and author of “Natural Swimming Pools”, I have added faith and professional support in the design.

If planning any ecological pool conversions of your own, PLEASE let me know and keep me posted as to your progress.



David W. Crimmins Permaculture Design

Available for Consultations in Arizona

For more about converting existing pools See:

* pool conversions

* Wet-Web Media Pool Conversions

* Erik’s Swimming Pool to Pond Conversion

“Natural Swimming Pools: Inspiration For Harmony With Nature” by Michael Littlewood.

How to Build a Natural Swimming Pool

Though fairly common in Europe, natural swimming pools (like the one pictured above in an Austrian family’s backyard), are in their infancy in the United States. Ask most American swimming-pool contractors to build a backyard pool and chances are they’ll roll out a long list of goods, including rebar, gunite, fiberglass, chlorine and an energy-sapping filtration system. But in recent years, a few builders and a growing number of homeowners have learned how to build pools without relying on a mass of manufactured materials and chemical additives. They’ve found it’s possible to construct pools that are more about building with nature and blending into the natural landscape. Natural swimming pools use gravel stone and clay in place of concrete or fiberglass, and aquatic plants instead of harmful chemicals and complicated mechanical filtering systems. The plants enrich the pool with oxygen, support beneficial bacteria that consume debris and potentially harmful organisms, and give habitat to frogs, dragonflies and other water life. The result is a beautiful, ecologically diverse system that is relatively inexpensive to construct. (A natural pool can he constructed for as little as $2,000 if you do it yourself, while conventional pools can cost tens of thousands of dollars.) Natural swimming pools require no harmful chemIcals, are fairly low-tech, and once established call for only a modicum of management. You won’t have to drain the pool each autumn. Except for topping it off now and then, you’ll fill the pool only once.

The cheapest and most ecologically sound way to build a swimming pool is simply to hollow a hole in the ground. You can make your pool as shallow or as deep as you want, but the key is to make sure the sides slope: Otherwise the soil will cave in. The ratio should be a 1-foot vertical drop for every 3 horizontal feet. “It’s not a bathtub effect, but more like a soup bowl,” says Tom Zingaro, partner with Denver-based Blue Lotus Designs, a pool-and pond-architecture company. One of the main reasons traditional swimming pools are constructed with a steel framework is to ensure the walls stay vertical and perpendicular to the bottom surface of the pool. Construct a pool with sloping sides and you’ll eliminate the need for any steel reinforcement.


Reserving at least 50 percent of your pool’s surface area for shallow plants, either at one end or in a ring around the sides, eliminates the need for chlorine and expensive filters and pumps. You’ll want to separate the swimming area of your pool and the filtration area, or plant zone (see the illustration). A rim within an inch of the water’s surface keeps plants in their place but allows water from the swimming area to move to the plant zone for filtering, As water passes through the fibrous root structure of the plants, bacteria concentrated on the plants’ roots act as a biological filter, removing contaminants and excess nutrients in the water. Decomposer organisms, also found in the plants’ root zones, consume the bacteria, effectively eliminating underwater waste buildup.

The BIOTOP Natural Pool.

Pure Pleasure for Body and Soul.

With the first natural pool in Austria in 1985 we had the pleasure of introducing a new world of outdoor enjoyment and swimming pleasure. 25 years in which we and our close-knit team have built more than 3,500 natural pools – for both residential and commercial customers.
Of course, with each new natural pool we increased our expertise and today this forms the most important basis for our product range which we can rightly say is unrivaled – and we intend to continue living up to this claim in the future.

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