How does a salt chlorine generator work?

A salt chlorine generator makes chlorine from the salt dissolved in your pool water. Water flows through a cell that holds electrically charged plates, the current splits the salt into chlorine, and the chlorine sanitizes the water and goes back to being salt. Pentair's IntelliChlor guide says the unit uses a process known as electrolysis to produce chlorine from a low concentration of salt added to the pool water.^[1] A salt pool is still a chlorine pool; the chlorine is simply made on site rather than poured in.

The parts

A typical system has two pieces. The cell sits in the return plumbing after the filter and heater. The control box, or power center, supplies the current and sets the output. Pentair describes the cell as containing bipolar electrodes that electrically produce chlorine when energized with DC current.^[1] Other brands arrange the parts differently, but the idea is the same.

What happens in the cell

Pool water carrying dissolved salt passes between the plates while the current is on. The reaction releases chlorine, which dissolves into the water. After the chlorine kills bacteria, oxidizes organic material and kills algae, it reverts back to salt, and the generator then reuses the salt.^[1] That is why you add salt rarely, mostly to replace what is lost to splash-out, backwashing and rain, and not to keep feeding the system.

The control board does more than switch the cell on. Pentair says its unit measures the water temperature and salt level to produce chlorine at the defined output.^[1] If the salt level in the pool water is too low, the cell is turned off until salt is added to the pool.^[1] Pentair recommends 3000 to 3500 ppm of salt for optimum water conditions and says its salt sensor reading is within +/- 500 ppm accuracy,^[1] so a handheld meter or test strip is a good cross-check.

Why the cell wears out

Chlorine production leaves scale, mostly calcium, on the plates. To fight it, the controller reverses the cell polarity, reducing calcium buildup, and Pentair notes that this self-cleaning cycle tends to reduce the life of the cell.^[1] Hard water speeds up scaling, and Pentair says high-hardness areas may need more frequent cleaning.^[1] Pentair says its cell is designed to operate for approximately 10,000 hours before replacement is needed or roughly five (5) years of average use.^[1] Treat that as that model's design figure, not a promise for every brand or pool.

What it does not do

A generator is not a complete water-care system. Pentair says its unit is designed only to produce chlorine and does not monitor or control chlorine levels in the pool or spa water, and that it is the owner's responsibility for monitoring and maintaining free chlorine levels at 1-3 ppm for pools.^[1] You still test the water, balance pH and alkalinity, and keep stabilizer in range. Salt itself also needs respect: the manual states that salt is an inherently corrosive material,^[1] so metal ladders, light niches and nearby stonework deserve attention.

When to call a licensed pro

The cell and plumbing look simple, but the power supply and the pump interlock are what make this equipment unforgiving. Never operate the generator without proper flow or water circulation, because a build-up of flammable gases will result in hazardous conditions.^[1] The power center must be wired so that it receives power only when the pool pump is on, because otherwise dangerous chlorine gas buildup can occur.^[1] The same manual says service should only be performed by a qualified pool service professional.^[1]

In Virginia no individual may work, or offer to work, as an electrical tradesman without a tradesman licence, unless working under the supervision of a tradesman licensed in that specialty.^[2][3] DPOR also says that if the work is valued at $1,000 or more, a valid Virginia contractor's licence is required for the licence category in which the contractor is to work.^[4] Check the licence before you hire.

To see what a bad cell costs, read how much a salt cell replacement costs in Virginia, or decide between fixing and replacing with should I repair or replace my salt chlorine generator. If you use a tablet feeder instead, see how to clean a clogged pool chlorinator. Browse pool and spa equipment answers or pool and spa businesses.

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