Saltwater Pools Guide
What is a Saltwater Pool?
Popularized in the United States during the 1980s, saltwater pools have continued to surge in popularity, with millions of salt pool systems now in operation.
Contrary to popular belief, a saltwater pool is not a chlorine-free pool. Pool salt water systems create their own chlorine by passing slightly salty water through two electrically charged metal plates inside of what's called the salt cell.
Through the process of electrolysis, salt (NaCl) and water (H~2~O), are converted into chlorine (Cl~2~), hydrogen (H~2~), and sodium hydroxide (NaOH), as the water passes through the energized salt cell.
When the chlorine molecule (hypochlorous acid, the same chemical produced by chlorine tablets and shock) is used up, it gets converted back to salt (NaCl), and the process can start again.
A saltwater pool is not necessarily better than a chlorine pool — because it is a chlorine pool. Salt pool systems create chlorine to kill bacteria, germs, and algae, and it's the same chemical produced by tablets, liquid, or granular chlorine.
Benefits of a Saltwater Pool
Saltwater pool owners love the soft and silky feel of the water, due to the approximately 3,000 ppm of dissolved salt in the pool. 3,500 ppm is the point at which human taste buds can start to sense salt, so you may not taste it, but can feel the difference.
Pools with salt water can often be easier to manage, as many salt system owners report reduced chloramine formation. Chloramines are the combined chlorine molecules that smell bad and can irritate your eyes. Indeed, most users of salt systems report much less of a harsh chlorine smell in the water or on their skin after swimming, as well as having no more "red-eye" swimmers. Some users also claim to have a more stable pH and Total Alkalinity, with less frequent adjustment needed.
Saltwater pools may be safer to operate, in that you have less direct contact with chorine products. In theory, you no longer have to buy, store, transport, or handle chlorine products ever again! In practice, however, many salt pool owners use pool shock for opening, closing, and periodic shock treatments.
Pool tablets or shock can also come in handy in case of pump or filter problems, as chlorine cannot be produced unless water is flowing through the salt cell. They can also be needed during cold weather, as chlorine can't be generated when water temperatures are below 60°F.
Setting Up a Saltwater Pool
Setting up a saltwater pool or converting your pool to a salt system involves more than just pouring salt in the pool. If you add salt without using a chlorine generator, then all you'll have is salty pool water.
But essentially, you just pour salt into the pool — a lot of salt. How much salt to add to the pool? To reach the initial salt level recommended by the salt system manufacturer (usually 2,400–3,200 ppm), you will need to add about 200 pounds of pure pool grade salt (NaCl), per 10,000 gallons of water. This dosage will get you to approximately 2,400 ppm salinity.
To calculate exactly how many bags of salt you'll need for your pool, use the following equation: 8.375 x Salinity Increase ÷ 100 = Pounds of salt per 10,000 gallons
Salt stays in the water, so you only need annual boosters to replace salt lost to backwashing or splash-out. You can use the equation above to figure out exactly how much salt to add to keep the pool salinity at an ideal level.
Installing a salt chlorine generator is also fairly straightforward. Most inground salt systems have a wall-mounted control box plugged into an electrical outlet, as well as an inline salt cell plumbed into the return line. The control panel allows you to dial in the desired amount of chlorine output, with indicators for water flow, temperature, and salt level. Salt chlorine generators for above ground pools often either hang on the pool wall or attach to the pool return for an even easier installation.
Turn on the chlorine generator. If the water temperature is above 60°F and water flow is sufficient, low voltage energy is applied to the salt cell. The cell then begins to produce chlorine until the desired chlorine output level is satisfied. Chlorine generators will turn themselves on and off as needed to create a consistent chlorine level. However, you still need to test your pool chlorine level regularly and adjust the output as needed.
Converting to a Saltwater Pool
To convert a traditional chlorine pool to a saltwater pool, you don’t need to drain the pool or do anything special. Besides normal, ideal water balance, all you need for a saltwater pool is a chlorine generator and enough pool salt to raise the level to the salt system manufacturer’s recommendation.
You will still need to maintain good water balance on a saltwater pool. Your pool pH, Total Alkalinity, and Calcium Hardness must be maintained by testing and adjusting the levels as needed, just as with a traditional chlorine pool. You will also still need to use Cyanuric Acid, also known as chlorine stabilizer or conditioner, to control chlorine degradation from the sun's UV rays. This will also prevent overworking your salt cell.
Maintaining a Saltwater Pool
There is very little difference in the day-to-day maintenance between salt pools and chlorine tablet pools. The biggest difference is that you’re not opening a chlorine bucket every week to fill the chemical feeder or floater. You still need to test and adjust your water balance and chlorine levels, you still need to use chlorine stabilizer, and may need other helper chemicals to maintain water quality.
There are some additional tasks that come with a saltwater pool, however. The energized plates of the salt cell attract calcium scale. Calcium deposits on the plates' metal surfaces over time, which ultimately reduces chlorine output and eventually damages the cell. Salt cells need to be cleaned regularly in a mild acid solution to dissolve the scale. Advanced inground salt systems are self-cleaning, accomplished by reversing the polarity to the salt cell, and sloughing off the scale, which is carried away by the water. However, even the most advanced salt cells can benefit from occasional cleaning to prolong their lifespan.
Salt is a corrosive mineral, and can damage soft travertine stone or stainless steel surfaces used on pool ladders and pool lights. Over time, salty water dragged off by swimmers can pit or erode soft stone surfaces on your pool deck. Sealing surfaces around the pool, along with regular cleaning for areas with low rainfall, can help protect soft surfaces from salt deposits. Pool ladders, lights, and other stainless steel items in the pool can also lose their luster as salt slowly oxidizes the steel. Sacrificial zinc anodes can be used in the pool or skimmer to draw the corrosive effects away from other metal surfaces. Salt can also damage the soft rubber used in pump seals and O-rings. Salt-resistant pump shaft seals are available, and O-rings can be protected with pool lube.
In addition to testing your Free Available Chlorine, pH, Total Alkalinity, Calcium Hardness, and Cyanuric Acid levels regularly, saltwater pools should be tested with salt test strips throughout the pool season. Salt does not evaporate, but is diluted by rain and fill water added to the pool, or when lowering the water level during backwashing or for winterization.
Cost of a Saltwater Pool
Salt pools need hundreds of pounds of salt, which is fairly inexpensive when purchased locally. The main cost of a saltwater pool is for the equipment, including the controller, sensors, and salt cell.
The cost of a chlorine generator varies according to the size of the unit. Many small above ground chlorine generators cost anywhere between $600–$1,200, while larger inground chlorine generators are priced from $1,000–$2,000.
More expensive salt chlorine generators have more features, such as the ability to shock — or superchlorinate — the pool. Some have a self-cleaning salt cell, capable of reducing calcium scale buildup through reverse polarity. Some also have an LED display of salt level and water temperature, as well as diagnostic lights for required service.
Over a 3–5 year lifespan, the salt cell will lose the metallic coatings on the electrolytic plates. When this happens, the chlorine output diminishes, and eventually the cell needs to be replaced. Replacement salt cells can be costly, up to half (or more) of the cost of the entire salt system.
Annual booster additions of pool salt are usually required, but only to replace salt lost due to backwashing, splash-out, or lowering the water for winter. If you fully drain the pool for maintenance, you will need to replace all the pool salt and start from scratch when you refill.
Over a 10-year time span, the cost of a saltwater pool vs. the cost of a chlorine-tablet pool can be surprisingly close. In other words, you won’t save a lot of money with a saltwater pool. The cost of the salt equipment offsets the monthly chlorine cost savings fairly closely.
Chemicals for a Saltwater Pool
As previously mentioned, saltwater pools are not chlorine-free, nor are they chemical-free. A saltwater pool is a chlorinated pool, but with an alternative delivery system. As such, you will still need other pool chemicals when using a salt chlorine generator.
Sanitizers: Most of your water sanitization will be taken care of with your chlorine generator. It can be helpful, however, to keep a small supply of chlorine tabs or granular chlorine on hand in the event of problems with the pump, filter, plumbing, or the salt cell itself. Salt pool owners also often use granular pool shock for oxidation, algae removal, or routine superchlorination. Many chlorine generators have a "Shock" feature. However, they are slow to act, and using this function creates a heavy demand on the salt cell, which may shorten its lifespan.
Balancers: Just like any pool, you need to pay close attention to pH, Total Alkalinity, Calcium Hardness, and Cyanuric Acid (stabilizer) levels in the pool. Chlorine-tablet-treated pools tend to gravitate towards the low end of the pH and Total Alkalinity scale, while saltwater pools tend to slowly rise in pH level, requiring pH reducer. Saltwater pools are most stable with a pH of 7.4–7.6, and a Total Alkalinity of 80–100 ppm. Most salt system manufacturers recommend a stabilizer level of around 50 ppm. High Calcium Hardness levels have no effect on saltwater pools, but a lower level in the 180-200 ppm range may result in less scale forming on the salt cell plates.
Other: Algaecides and clarifiers may be needed on occasion, as with any other pool. Algaecides are great helper chemicals for chlorine, as it dissolves protective layers on algae, allowing chlorine to penetrate deep into the nucleus. Clarifiers are helpful for pool filters that are undersized, underperforming, or simply not running long enough each day. They can also be helpful after a spring startup or algae cleanup.
Water Testing in a Saltwater Pool
Just like any other pool, you will need a good test kit to monitor chlorine and water balance levels. Most importantly, the pH and Free Available Chlorine level should be tested at least once per week. Salt chlorine generators can be set to a certain output level, but increased pool usage and changes in weather or temperature can use more chlorine than the system creates. This is why it's important to test the chlorine level in a saltwater pool often, and adjust the output as needed.
In addition to testing a saltwater pool for pH, Total Alkalinity, Calcium Hardness, and Cyanuric Acid, you also now need to test the salinity level, or the amount of salt in the pool. This is measured in parts per million, or ppm. Many inground units monitor salt level, and some display the salt level or have "Low Salt" indicator lights. Even so, testing with salt test strips is still a good idea, in order to calibrate or double-check the salt sensor readings.