Salt water pools have become popular over the past ten years. The main reason for this is the belief that salt water is a healthier alternative to chlorine treated pools. This is a myth.
Salt water pools use a device called a salt chlorinator to convert salt in the water into liquid chlorine. In reality, salt water pools have the same amount of chlorine as pools treated with chlorine directly, which is typically 1ppm to 3ppm.
Pool Ionizers release microscopic mineral ions into the water that control bacteria and algae. This allows you to lower the chlorine concentration to 0.6ppm. According to the EPA and Health Canada, ionized pools or ‘mineral pools’ are the only types of pool where you can safely reduce the chlorine concentration.
This post compares salt water pools with mineral pools that use a pool ionizer.
Salt water pools use a device called a salt chlorinator. The salt chlorinator consists of a salt cell and a control box. The salt cell is plumbed into the pool plumbing on the line that returns filtered water to the pool.
The salt cell is connected to an electrical control box which is mounted near the cell and close to a power outlet.
Pool ionizer configurations are very similar. A mineral cell is plumbed into the return line of the plumbing and is connected to a control box.
The figure below illustrates the installation of a pool ionizer system. The blue tee houses the mineral cell which is threaded into the bottom of the tee. The mineral cell is then connected to a control box which is plugged into a regular wall outlet.
With a salt chlorinator, you add salt to the pool, rather than chlorine. Several large bags of salt are required to kick off the chlorination process. The salt cell then converts the salt to liquid chlorine, effectively creating a mini chlorine factory. Once the chlorine is used up, it is then converted back into salt, so you will only need to top up the salt occasionally.
Most salt chlorinators also have a ‘burst’ function which is like a shock, so you typically don’t need to use a chlorine or non-chlorine based shock. However, you can use shock with a salt chlorinator if required.
Since liquid chlorine has a high pH, you will need to use a pH balancing chemical to bring the pH down on a regular basis. This is critical because chlorine does not work effectively if the pH is high. Salt chlorinator manufacturers and pool professionals typically recommend testing and adjusting pH every week.
It is also important to keep the chlorinator settings low if your pool is going to be covered for a long period of time. Chlorine burns off in the sun, so if your pool is covered, the chlorine level can get extremely high which can damage your cover, liner, pool edges, and anything else in the water.
With salt chlorinators, it is important to clean the salt cell regularly. The fins on the cell get scaled up over time and need to be cleaned with muriatic acid. Generally, once per season is enough. However, if your water is really ‘hard’ meaning there is a lot of ‘dissolved solids’ or sediment, you will need to clean the salt cell more frequently.
Pat from Leisure Industries explains the difference between pool ionizers and salt chlorinators
Pool ionizer systems add microscopic mineral ions to the water. It takes up to two weeks to build up the ions, so this can be a tedious process at first. However, once they have reached the desired level, which is typically 0.2ppm to 0.4ppm, they are very stable so you don’t have to test it very often. Also, modern pool ionizer controllers make it easy to ramp the ions up if you follow the directions.
Mineral pools also require a residual of 0.6ppm of chlorine. This is used to burn up organic material that gets into the water from bathers (lotions, skin, hair, etc.) and the environment.
The easiest way to deliver chlorine in a mineral pool is with an inline chlorinator. The chlorinator hooks into your plumbing and provides a reservoir for adding several chlorine tablets at once. There is a dial that allows you to set the chlorine output. Since the chlorine requirement is so low on a mineral pool, this can usually be set at 2 or 3 out of 10.
Mineral pools also require the occasional shock, usually after heavy usage or after a rainstorm washes organic materials into the pool.
If you have ‘hard’ water, or a large amount of dissolved material in the water, the mineral cell plates may get scaled up. This is usually not a problem because the microscopic ions can still get through. However, if there is a large amount of scale on the plates, you can file it off with a metal file.
Salt chlorinators cost between $500 and $2,000 to set up, depending on the manufacturer. The brand name Hayward and Pentair systems are at the higher end of this range.
If maintained properly, the cell that converts salt to chlorine will last 4 to 5 years. The replacement cells cost between $300 and $1,000, depending on the manufacturer.
Apart from the system, you will have to factor in the cost of chemicals. This is primarily the salt, pH balancing chemicals and acid for cleaning the salt cell. Since the salt is very stable in the water, you should not need to add much after the initial start-up. However, pH balancing chemicals are used frequently.
Pool ionizers cost between $300 and $2,000 to set up, depending on the manufacturer.
On a larger pool (above 25,000 gallons), you will have to replace your mineral cell every season. You can get two or more seasons out of a cell on a smaller pool. The replacement mineral cell costs about $90 to $150.
Mineral pools also require a low residual of chlorine. The amount of chlorine required depends on the size of your pool, usage, sun, rain, etc. We typically recommend adding one 3” tablet every week or two which is less than half of what you would need without an ionizer.
If you are converting a chlorine-only pool over to a mineral pool, a good rule of thumb is to divide last years’ cost of chlorine in half. You should use less than that, but this is a good estimate.
The biggest risk with salt chlorinators is corrosion to pool surfaces and equipment from the salt in the water. Some manufacturers of above ground pools and equipment will void your warranty if you use a salt chlorinator, so it’s important to check that before you go with this system.
If you are having a new pool installed, it is important to have it ‘bonded’. This means that all of the metallic components like pumps, heaters, ladders and light fixtures are connected together with a wire. This helps divert the stray electrical currents generated by the chlorinator which can cause corrosion.
If you have an older pool where the components are not bonded, you are likely to get rusting and corrosion to your equipment, which can be very costly to fix. Also, if your liner has a leak and your inground pool uses steel panels, like most do, you could get rusting of the panels which is extremely costly to fix.
Salt water can also be corrosive to stonework. If you have stone on your pool deck, you may need to apply a special sealant to make sure it doesn’t get damaged by the salt water.
The biggest risk with pool ionizers is discoloration of your pool lining from the minerals in the water. This is very rare with modern systems which are computer controlled. However, it is important to test the mineral level in the water regularly to make sure it is in the recommended range. It is also important to test the pH regularly because when it goes out of the typical range, the minerals collect on surfaces more easily.
With salt chlorinators, you don’t need to add chlorine to the water. The electronic chlorinator generates this for you by converting the salt in the water to liquid chlorine.
The continuous generation of chlorine is great at eliminating the chlorine byproducts that arise when chlorine attacks organic matter. These byproducts are what cause most of the chlorine smell in pools, so usually salt water pools have less chlorine smell.
The salt in the water also gives it a soft feel.
Pool ionizers add natural minerals to the water which control bacteria and algae. This allows you to reduce the chlorine concentration to around half of what you would need in a salt water or traditional chlorine pool.
Since chlorine is linked to asthma and other respiratory illnesses, this chlorine reduction is the biggest benefit for pool ionizers.
Mineral pools are usually less maintenance than chlorine or salt water pools. This because the minerals are always active in the water controlling algae and bacteria. The algae in particular is what usually gives the water a cloudy look. Pools with ionizers stay crystal clear all summer, even if you forget to add chlorine, because the minerals are always in there working.
Mineral pools usually stay within the typical pH range which means you don’t need to store harmful muriatic acid used for balancing pH.
To give the water a ‘softer’ feel, you can use a borates-based product which provides that salt-like feel without the salt.
Finally, with mineral pools there is no risk of property damage or corrosion.