One of the most common trends in the swimming pool industry over the last few years has been the popularity of salt water swimming pools. Many of us in the swimming pool industry have been inundated with questions about salt water swimming pools—hopefully the following information will help answer your questions.
What is a salt water pool?

A salt water pool is a pool which has a purification system (also called a chlorine generator) that provides on-site production of chlorine.

Chlorine generators reduce the need to purchase and apply chlorine to your pool on a regular basis. Basically, instead of adding chlorine on a regular basis, you add salt periodically which is converted to chlorine.
How does it work?

The way it works is this: Salt is added to the pool and the salt water passes through an electrolytic cell, where electricity is used to separate the sodium and chlorine molecules. This, in turn produces hypochloric acid, the killing form of chlorine. Once the chlorine is used it combines with sodium molecules and returns to salt and the whole process begins over again.

Often times, pool companies tend to omit the cons when selling a salt water system—and it is important that consumers understand the pros and cons of salt water systems. Based on our experience, following is a list of pros and cons of salt water systems:
Pros of salt water pools
The feel of the water on the skin

This is probably the biggest advantage of a chlorine generator. Owners of chlorine generators talk about how soft and smooth the water feels.
Better water quality

Better water quality is maintained because the unit is chlorinating continuously when the pump is in operation.
Less eye irritation

Most report less eye irritation when using chlorine generators.
No need to purchase chlorine

Other than rare situations, there is no need to purchase chlorine. The exceptions to this are: chlorine generator is not producing enough chlorine (due to extremely high water temperature, heavy swimmer load, rain, etc.), chlorine generator is not working, chemical imbalance, etc.
No need to store and handle chlorine

Other than the rare situation listed above, storing and handling of chlorine will be limited.
Cons of salt water pools
Initial cost

Chlorine generators are often sold as a cost-savings system, which is not a true statement in most situations. The installed price for a high quality residential chlorine generator is typically $1,500-$2,000. True that you no longer have to buy chlorine, and salt is less expensive than chlorine, but at $1,500-$2,000, you could buy chlorine for 5-8 years.
Cell replacement cost

Chlorine generators are mechanical devices, and as with any mechanical device—they can break down. The most common failure of chlorine generators is the salt cell, which typically last 3-5 years (depending on use and maintenance) before needing replacement at an average cost of $600-$800.
A salt water pool is not chlorine-free

A “salt water pool” is still a chlorine pool. The chlorine production in a salt water pool is essentially sodium hypochlorite (liquid chlorine). If you are truly allergic to chlorine, then this is not the system for you.
Increase in electrical costs

A chlorine generator only produces chlorine when the pump is operating, so it is important to operate your pump a sufficient amount of time to produce the amount of chlorine that is needed for your pool. This amount of time will increase under the following conditions: high water temperature, heavy swimmer load, pets that swim, rain, chemical imbalance, etc.

Running your pump for longer periods of time will result in an increase in electrical costs.

Example: A conventional 2hp pump in the Denton area costs approximately 25 cents per hour to operate. If you have to increase your pump run time from 8 hours per day to 16 hours per day, that is an increase in your electrical costs of $2 per day, or $730 per year.
Salt can be corrosive

Salt can be corrosive to coping (especially flagstone), stone waterfalls, decks, and any metal (such as diving board bases, pool ladders, slide legs, poolside furniture, stainless steel filters, etc.). To help slow down this corrosion process, the application of a penetrating sealer to coping and stone waterfalls seems to help. This penetrating sealer needs to be applied at a minimum of once annually. In addition, we recommend rinsing off your coping/decks/metal with fresh water after using the pool.
Not environmentally friendly

Due to the salinity of the water and its potential harm to sensitive plants and fish, many municipalities have restricted the backwashing or draining of salt water pools into the storm sewer system.
They do not provide complete pool care

Often times owners of salt water systems depend on the system to provide complete pool care—they do not. Water testing and cell cleaning/replacement are very important.

Water testing

Chlorine generators only produce chlorine, they do not maintain the water chemistry of the pool. The pool water must still be tested and balanced as needed. We recommend the following testing regularity and ranges:

Test weekly

chlorine—2.0 to 4.0 ppm
pH—7.2 to 7.6
total alkalinity

80 to 100 for calcium hypochlorite, salt, and liquid chlorine pools
100 to 120 for dichlor and trichlor pools

salt level—2700 to 3500 (check with the manufacturer of your chlorine generator to confirm)

Test monthly

calcium hardness—200 to 400 ppm
cyanuric acid

30 to 90ppm on chlorine pools
70 to 90 on salt pools

It is also important to note that salt raises pH—which means more muriatic acid will be needed to keep the pH in the proper range.

Cell cleaning/replacement

Like any mechanical device, chlorine generators must be maintained—most manufacturers recommend that the system’s cell be cleaned every six months. Salt cells typically last 3-5 years, depending on use and maintenance. Salt cell replacement typically costs approximately $600-$800, depending on the brand.
Can cause scale forming deposits on the tile/spa spillways/waterfalls

The use of salt can cause scale deposits to form on tile/spa spillways/waterfalls. Frequent brushing of these areas and use of a scale inhibitor are both recommended to prevent this scale build up.
Does not work in cold water

Chlorine generators do not produce chlorine when the temperature reaches a certain level (approximately 55 degrees). When this occurs, the use of chlorine will likely be necessary in order to prevent problems.

What is our overall opinion of chlorine generators? Like anything, it has pros and cons and if you are aware of them and take them into consideration, a salt water system can be a very good alternative in the right situation.