Chlorine Generators

One of the first alternative sanitizers introduced to the pool and spa industry was the chlorine generator. Chlorine generators are attractive to pool owners simply because they eliminate the need to store, buy, transport and handle chlorine. They are not an alternative to chlorine, but actually make their own chlorine from regular table salt. The pool water passes through a generator cell that creates the chlorine within the pool water.

How Does It Work?

As pool water passes through the chlorine generator cell, pumped through by your filter pump, the salt in the water is turned into Hypochlorous acid. Hypochlorous acid is the exact same component that is produced when any chlorine is added to pool water, whether you use sticks, tablets, granular or liquid. As the water returns to the pool, it will introduce the newly produced chlorine, preventing algae, bacteria and killing micro-organisms, creating a safe and sanitary swimming environment.

OK?  How does it really work?

This mild, pleasant saline water is sanitized through the process of electrolysis, as mentioned above. The electrolytic cell, through the use of a small electric current, breaks down the water into its basic elements, Hydrogen and Oxygen. By adding small quantities of granulated salt (much like household table salt - NaCI), Hypochlorous Acid (common chlorine) is produced. During the process, the Hypochlorous Acid (Chlorine) is ultimately converted back to salt. Thus, the salt does not get "used up". Salt only needs to be "topped off" once or twice a year and only to replace salt lost due to water splash-out, bather drag off or filter backwashing.

Salt in My Pool?

The salt level required to maintain a safe, chlorinated pool is about 2500 to 4000 PPM (parts per million). The human body cannot taste salt until the PPM is around 5000. As a reference point, the ocean is around 40000 ppm. The amount of salt in the pool is usually not noticeable. Once the salt is added to the pool, there is no need to add salt on a yearly basis unless the pool is drained or a significant amount of water is removed. Also, the salt level is low enough so there is no danger of equipment corrosion. Chlorine generator users also report the water is softer, leaving a more refreshed feeling after swimming.

Is There Any Maintenance Required?

Chlorine generators require very little maintenance. We at Poolcenter.com recommend the generator cell be removed and cleaned on a yearly basis, usually at start up. Remove the cell from the pool plumbing and run a plastic brush through the cell. For calcium deposits, a mild solution of muriatic acid and water will do the job, or to be careful, use the Lo-Chlor Green Cell Plus. The power supply unit requires no regular maintenance.

Frequently Asked Questions

What Type of salt do I add?

Avoid Rock Salt as it contains too many impurities! Acceptable salts include Food grade salt, Water softener pellets, Solar salt flakes, Water conditioner salt, or Brine blocks. Make sure that your salt contains no iodine and is as pure as possible. Sure Soft Pool Salt is accepted by all Chlorine Generator manufacturers.

Where do I add the salt?

What is most important when adding salt is to brush it around until it is dissolved. This is accelerated by turning your pump on, opening the bottom drain and adding the salt over the drain, rather than walking around the perimeter while adding the salt. It is recommended that you continue to run the pump for 24 hours so the salt can spread evenly throughout the pool. With Granular salt, 60 - 70% will have dissolved before hitting bottom. The remaining salt can simply be brushed into the drain which will then complete dissolution. With all other forms of salt, it will take longer to dissolve but the same process will accelerate the dissolve rate. Simply brush the salt in a pyramid pattern over the drain to increase dissolution.

How much salt do I add?

Enough for 4000 ppm (parts per million) as a starting point. So depending on the initial salt level of your water, you only add the amount needed to establish 4000 ppm. For new pools or freshly filled pools, the salt level will most likely be zero. In this case, 50lbs of salt per 2,000 gallons of water will establish 4000 ppm. For existing pools, the previous usage of chlorine bleach or tablets will have already introduced a level of salt into the water. Have the water tested first then add the appropriate amount to establish 4000 ppm. You can test the salt level of your pool using salt test strips, or your local pool store may have the ability to test a sample for you.

What happens if I add too much salt?

Over-salting will not harm your chlorine generating system, but will lead to a salty tasting water. For some, this is not undesirable as it will more closely match our bodies natural salinity level, making it more comfortable to swim in. If it is too excessive (over 6000 ppm), you can sustain corrosion damage to metallic equipment such as stainless steel handrails, ladders and filters, light rings, or copper heat exchangers. To reduce the salt level, dilution is the solution. Drain some water and refill with fresh water.

How often will I need to add salt?

After the initial dosage of salt, you will only need to add salt when necessary. The most common ways salt is lost is through leaks, rainwater overflow, filter backwashing, and bather splash-out/carryout. Normal water evaporation does not lose salt, it increases the concentration. The make up water added to bring the water level back to normal will then reduce the salt concentration back to 4000 ppm. Most chlorine generator units have low salt indicators, with Digital Units going further to provide the user with the proper salt amount needed to reestablish 4000 ppm.

Do I eliminate the need to add chemicals?

Chlorine generators do one thing, generate chlorine. However, the purity of this chlorine has less effect on the overall water chemistry balance; therefore, FEWER chemicals are needed re-balance the water. Poolcenter.com recommends periodic (weekly or bi-weekly) testing of stabilizer levels (60 - 80 ppm), Free Chlorine (2 - 4 ppm for pools and 3 - 6 ppm for spas), pH (7.2 - 7.6), and salt levels (2500 - 4000 ppm). Since salt generating chlorine systems do not affect  the Total Alkalinity or Calcium Hardness, a monthly check is sufficient. In some cases, you might still need to add chlorine for shocking purposes due to extremely heavy bather loads, rainstorms, or accidents, (fertilizer, excessive organic debris or human waste). Shocking the pool will not affect your chlorine generator.

Will I have to run my equipment more?

Your chlorine generator does not rely upon a higher salt level AND extended pump run times in order to generate enough chlorine, provided the cell is properly sized to the pool. Most units allows for multiple configuration set-ups so that you can generate sufficient amounts of chlorine during your current pump circulation time. For regions that have short circulation times, you can increase the output power of the generator to compensate.

How long will the cell last?

The residential cell is rated for approximately 10,000 hours of operation. This typically translates to 3 - 5 years, depending on pool volume, cell size and the sanitizer demands of your pool. Water chemistry balance, salt levels and stabilizer levels are all key factors in ensuring maximum cell life. Proper water chemistry is the key here. The harder you use the cell, the more you ask of it, the shorter its life span. Annual inspection and cleaning of your salt cell is one of the best things you can do to help delay cell degradation.

What chemical levels do I need to test for regularly?

The four main tests to perform with a test kit are pH, chlorine (or other sanitizer residual), Total Alkalinity and Calcium Hardness. Cyanuric Acid levels, mineral content, Total Dissolved Solids and Acid or Base Demand tests may also be performed as needed.

How often do I need to test the water?

I should say everyday, but I realize that's a bit much for most people. Commercial pools are required to check chlorine levels every hour and record their findings in a log, however the "backyard lifeguards" should check their pH and chlorine levels at least 2-3 times a week. Chlorine should be fed continuously through a feeder device to maintain a consistent level. Total Alkalinity and Calcium Hardness levels tend to fluctuate less, so weekly testing should be O.K.

What are the recommended levels?

• pH: 7.2 - 7.8
• Chlorine: 1.0 - 2.0 ppm
• Total Alkalinity: 80 - 120 ppm
• Calcium Hardness: 180 - 220 ppm, though some say 200 - 400.
• Cyanuric Acid: 25 - 50 ppm
• Total Dissolved Solids: 500 - 5000 ppm

How long do my reagents last?

Typically one season. Reagents lose their strength over time and can also be ruined by direct sunlight and temperature extremes. Replace your reagents annually.

Can I use reagents from other test kits with my test kit?

No; drop size, concentration and color variation will provide inaccurate results.

Can I use a chlorine test kit for bromine?

If you have a DPD test kit, you need simply multiply the test result by 2.25 to obtain the bromine equivalency. This works because bromine is over twice as dense as chlorine.

My test kit shows no Chlorine, even though I know it's there...

If chlorine levels are excessively high, the content can bleach out DPD, a reagent commonly used for chlorine testing. Either dilute the sample with chlorine free water, or double the # of drops of DPD, and multiply or divide accordingly.

There has been evidence that excessively high levels of stabilizer, or cyanuric acid, can cause a phenomenon called chlorine lock. Levels above 100ppm of cyanuric acid (CYA) may prevent chlorine from registering and possibly sanitizing. Lower CYA levels by dilution.

If you smell chlorine in the water, you are very possibly aware of combined chlorine, known as chloramines. These will not register in a test for free chlorine. A good DPD test kit will allow you to test for total chlorine levels and free chlorine levels; the difference being the combined levels. If trace amounts of combined chlorine is above .3 ppm, you may need to shock the pool to break the bond of chloramines; this shock level is around 30 ppm.

When I test for pH, I get a purple color...

If your reagents are in good condition, a purple color in a pH test is an indication of chlorine levels being too high and interfering with the test. Add a drop of thiosulfate reagent to remove the chlorine from a new sample, and test again.

What type of test kit do I need?

There are many different types of test kits commercially available. If you are concerned about water balance, (and you should be) you will want to spend more for a nice kit. The basic "duo" test kits, available for about five bucks, are usually OTO chlorine and pH testers only. You may wish to spend more for a DPD chlorine kit, which measures free, combined and total chlorine levels (OTO measures only free levels). Also important is the ability to test total alkalinity and calcium hardness. Acid demand and base demand tests will allow you to perform a titration test on your pH sample. Simply count the # of drops to determine, with the help of a chart, exactly how much acid or base is needed to adjust the pH. A "four-way" test kit will test pH, chlorine, alkalinity and acid demand. Test strips are available now with "Litmus test" technology. These are "dip & read" strips of paper that turn colors indicating levels of pH, alkalinity and chlorine in the pool. Fairly simple to use, however, it seems that they may not be quite as accurate. Your pool professional can check the water for metal presence, cyanuric acid levels and TDS (total dissolved solids). If you have a biguanide water treatment system or a chlorine generator, you'll obtain special test kits from these dealers.

A chemical called sodium tetraborate sold under the name Proteam Supreme, this chemical is a EPA registered algaestat that also reduces eye and skin irritation. Proteam also claims to give water a softer feel and prevent pink algae, which is actually a bacteria. ProTeam is a helpful ingredient in a chlorine-free program, utilizing Nature2 Technology.

What the chemical does is prevent organics like algae from processing carbon dioxide. It is added in 2 half doses of 2 lb per 1,000 gallons. Periodic additions of the product are made for backwashed and splashed-out water. A test kit is available for testing levels of potassium tetraborate in the water.

Proteam claims a chemical reduction of up to 50% is obtainable when using the product, and the water's clarity is improved by increasing the water's capacity to hold calcium in solution. This product is a recommended by the Claritec people, and the Pool Janitor.

Originally developed as a pre-surgery anti-microbial scrub, PHMB was patented in 1977, and marketed for pools and spas under the trade name Baquacil. This technology has the distinction and the EPA approval as the only non-halogen sanitizer available for pools and spas. Here's a page if you're looking here to find out how to convert back to chlorine or some other sanitizer.

Now that the patent has expired, Bio Lab has also introduced a line of biguanide products under the name Soft Swim. A full system for complete halogen free water care, these products are a stand alone alternative to traditional sanitation methods. The Biguanide itself is combined with algaecides and hydrogen peroxide for periodic oxidation. The system tends to gum up filters, and of course a product is available to de-gum it. Biguanide are not recommended for spas or aerated pools. As long as you don't add any other chemicals but those recommended by the manufacturer, you'll do fine; but add a small amount of chlorine and your pool looks like orange sherbet! Biguanides are also incompatible with TSP, ozone, detergents, ionizers, and other common chemicals, but is not at odds with any water balancing chemicals you may add.

Biguanides have been reported to be easier to use, with less chemical level testing, and less adding of chemicals. The water doesn't smell of chlorine of course, and the reduced surface tension gives it a smoother feel. It doesn't degrade with sunlight, temperature, or changes in pH levels like chlorine. At recommended concentrations, biguanides won't irritate the skin or eyes and can't corrode pool equipment.