· by Michael Blair, Nashville's Pool & Spa
The common misunderstanding is that saltwater pools do not use chlorine. They do. A cell in the plumbing electrolyzes the salt dissolved in the water and makes chlorine from it, which is why a University of South Carolina study of salt water pools describes them as electrochemically generated chlorine and measures them against liquid chlorine, which it calls the most commonly used pool disinfectant.
What changes day to day with a salt pool?
What changes is where the chlorine comes from. The cell makes it on site, so there are fewer jugs and tablets to buy, store and pour. The U.S. EPA’s consumer guide to pesticide devices lists certain pool and spa electrolysis units among the devices it oversees, and says a generator sold together with salt may be regulated as part of a pesticide product, which tells you how the regulator sees one: equipment for making a disinfectant.
On comfort, the best evidence we found is a survey of 1,001 swimmers at 20 indoor pools in Spain. Swimmers in chlorine-treated pools were more likely to report eye and skin irritation, dry skin and breathing complaints than those in pools using other methods, and salt electrolysis was among the methods linked with fewer complaints and more satisfaction. Those were public indoor pools and what people said they felt, so we read it as a fair hint about eyes and skin and make no promise about how the water feels to the hand or what it does to swimwear.
Testing does not change. We test and balance a salt pool on weekly service the same way as any other, pH, alkalinity, stabilizer and calcium, with the salt level added to the readings. If the water clouds up anyway, our post on cloudy pool water walks through what to test.
What it costs
A salt system is equipment bought on top of the pool: a control unit and the cell that does the work. The cell is the part that wears, and how long one lasts depends on the make and model, so we go by the manufacturer’s manual for the unit in front of us rather than quoting a number of years.
Whether salt works out cheaper to run than buying chlorine depends on the pool, the equipment and how hard it is used, and we have no local figure we would put our name to. Prices for the work itself are in our guide to what pool and spa work costs in Nashville.
The salt deserves a moment’s thought for another reason. The South Carolina researchers followed one indoor community pool before and after it switched to salt: total disinfection by-products rose 15% while their calculated toxicity fell, and bromide impurities in the sodium chloride used to make chlorine led to a 73% increase in brominated by-products. That is a reason to buy salt meant for pool chlorinators and to check what the cell’s manufacturer asks for.
- Saltwater pools still use chlorine, generated on site
- The cell wears out, and its life depends on the model
- pH still needs testing and adjusting
- Metal fittings and stone are worth asking about before converting
- Every other reading still gets tested and balanced
Is salt water hard on metal fittings and stone?
It can be, depending on the part, so anyone converting an older pool should ask whether salty water will be hard on its metal fittings, ladder, light niche or natural stone coping. There is no general rule we would stand behind here. The answer for each part comes from what it is made of and what its manufacturer says about salt water.
On a pool built with salt in mind, those choices were made at the start. On a conversion we look at the materials and the equipment first, and if the coping is due for replacement anyway, a renovation is the time to pick something chosen with salt water in mind.
pH drift
You will often read that making chlorine from salt pushes pH upward, so salt pools need acid more often than chlorine pools. We have not seen a measurement we could cite for that, so we treat it as something to watch rather than a rule: pH gets tested on schedule and acid goes in when the reading calls for it, as on any pool.
The fair summary is that a salt pool means less handling and the same attention. If you are thinking about converting yours, send us a few details about the pool and we will look at the equipment and the materials before recommending anything.
Sources
- Granger and Richardson, University of South Carolina, Do DBPs swim in salt water pools? (J Environ Sci, 2022) — Salt water pools are electrochemically generated chlorine; liquid chlorine the most common disinfectant; one indoor pool: total DBPs up 15%, calculated toxicity down; bromide in the salt led to a 73% increase in brominated DBPs
- U.S. EPA, Pesticide Devices: A Guide for Consumers — Certain pool and spa electrolysis units listed as devices; a generator sold with salt may be part of a pesticide product
- Fernández-Luna et al., Perceived health problems in swimmers according to the chemical treatment of water in swimming pools (Eur J Sport Sci, 2016) — Survey of 1,001 users at 20 indoor pools in Spain; more perceived eye and skin irritation with chlorine; salt electrolysis linked with fewer perceived problems and greater satisfaction
FAQ
Saltwater or Traditional Chlorine — questions
Is a saltwater pool chlorine free?
No. A cell makes chlorine from the salt in the water, so the disinfectant is chlorine either way, and what changes is that you are not buying, carrying and dosing it yourself. The chlorine is the same, though the water is not identical in every respect: a University of South Carolina study of one indoor pool found a different mix of disinfection by-products after it switched to salt.
Does a saltwater pool need less maintenance?
Less chlorine handling, yes. The testing does not go away: we still check and balance pH, alkalinity, stabilizer and calcium on a salt pool, and the salt level as well. pH deserves close attention, since it is often said to creep upward on salt systems. It is easier rather than hands-off.
Will salt damage my pool or decking?
It depends on what the pool and deck are made of. Metal fittings and natural stone coping are the parts worth asking about, and the answer for each comes from its manufacturer’s guidance on salt water rather than a general rule. On an older pool being converted, check compatibility before the cell goes in rather than assuming it.
Can you convert a chlorine pool to saltwater?
Yes, by adding a salt system: a control unit and a cell in the plumbing that makes chlorine from dissolved salt. Before the cell goes in, we check the metal fittings, ladder, light niche and any stone coping against their makers’ guidance on salt water, and we use salt meant for pool chlorinators.