Salt Cells, Chlorine Output and Water Care

The cell is the expensive part of your pool. Everything on this page exists to help you keep it alive longer than the three to five years most people get.

River Pools puts a well-maintained cell at three to seven years and $700 to $1,100 to replace. Retail prices at Leslie’s run from $699 for a small Hayward unit up to $1,949 for a Jandy AquaPure 1400. That spread between three years and seven years is mostly down to water chemistry and how often anyone looks at the plates.

The question this hub answers

Almost every salt pool problem arrives as one of three things wearing the same costume: a LOW SALT light, no chlorine in the water, or a reading that disagrees with a test. In each case there are three candidate causes, and people reliably guess the wrong one.

1. The salt really is low. Least common in an established pool, because salt does not get used up.
2. The cell is degraded or dirty. Very common, and it produces both low-salt warnings and low chlorine.
3. The reading is wrong. Also very common, and it comes from scale, cold water, low flow, or the wrong cell model set in the menu.

Work them in that order and check the cheap things first. A sequence that takes fifteen minutes:

• Read the displayed salinity, then run a titration test on a fresh sample. Note both numbers.
• Check the cell type configured in the control panel against the label on the cell you actually own.
• Look at the plates with a flashlight. Scale looks like white crust. Clean plates are dark grey and smooth.
• Note the water temperature. Below roughly 60°F most systems cut output, and many stop near 50°F.
• Check your flow. A dirty filter, a closing valve or air in the line all starve the cell.
• Only then consider adding salt.

Owners who skip straight to step six are the ones who end up at 5,000 ppm with a dead cell and a drain hose. The comment thread on Inyo’s guide to reducing salt has the pattern in the owners’ own words, including one who wrote: “I added to much salt to my 15000 gallon pool because I did not realize my T-cell was going bad.”

Cleaning the cell

Scale is the main thing that shortens a cell’s life and the main thing that produces false low-salt readings. It builds faster when calcium hardness or pH run high, which is why the chemistry pages below matter more than they look.

Inspect every two or three months during the season. Most self-cleaning cells reverse polarity on a schedule to shed scale, and that works until it does not. The job itself is a dilute acid soak, not a scrub with anything metal, and the dilution ratio matters more than the soak time.

One Intex owner described the false-alarm version exactly: “plates are crystal clean, tons of salt in the pool but still after running for 15 mins get the low salt error so frustrating!!” (intexpoolsite). Clean plates plus a persistent low-salt error points at flow, temperature, the cell setting, or plate wear you cannot see.

Detailed pages in this hub:

• How to clean a salt cell
• Acid washing a cell: dilution, timing and what it costs you
• Cell replacement: when to, and when not to
• How long does a salt cell last

Cyanuric acid, which behaves differently here

This is the part that catches people converting from a chlorine pool.

Cyanuric acid shields free chlorine from sunlight. In a manually chlorinated pool the usual range is 30 to 50 ppm. In a salt pool, the widely used range is higher, around 70 to 80 ppm, because the cell produces chlorine slowly and continuously rather than in a daily slug. More CYA means less of that chlorine burns off in the afternoon, which means the cell can run at a lower output percentage and last longer.

Run CYA too low and you will chase chlorine all summer and wear the cell out trying. Run it too high and your chlorine stops being effective at normal levels, which produces the classic complaint: salt is fine, the cell is running, and the water still goes cloudy or green. One PoolForum poster had salt at 3,100 and free chlorine “practically zero,” with CYA pushed to 70 by stabilizer tied in a sock in the skimmer.

Pages in this hub:

• Cyanuric acid in a salt pool: why the rules are different
• CYA levels for a salt pool, and the ideal range
• How to lower cyanuric acid
• How to raise cyanuric acid
• Symptoms of high cyanuric acid

pH, and why it always climbs

Salt pools drift upward in pH, reliably, and it is not a fault. The cell generates hydrogen gas as a by-product, and that aeration drives dissolved carbon dioxide out of the water, which raises pH. The electrolysis itself is close to pH neutral; the off-gassing is what moves the number.

The practical consequence is that you will add acid more often than a chlorine pool owner does, and that letting pH sit high is what grows scale on your cell plates. High pH is therefore not a cosmetic problem in a salt pool. It is a cell-life problem.

Pages in this hub:

• Why pH creeps up in every salt pool
• pH in a salt pool, and how to bring it down
• Salt water pool chemicals: what you actually need

Chlorine output and run time

Two dials control how much chlorine you get: the output percentage on the generator and the hours the pump runs. A cell only makes chlorine while water is moving through it.

If chlorine is low, raising the output percentage is the obvious move and often the wrong one, because it works the cell harder for the same hours. Usually the better fix is more pump hours at a lower percentage, or getting CYA into range so less chlorine is lost. One owner’s “no chlorine” problem on the Inyo forum turned out to be neither: “It was a scheduling issue on our control box.”

Pages in this hub:

• Optimal chlorine levels in a salt pool
• How to increase free chlorine in a salt water pool
• Can you shock a salt water pool

Water problems that get blamed on salt

Green water, cloudy water, algae and stains are chemistry problems, not salt problems, but they show up in salt pool searches because the salt system is the thing the owner can see. Each has a likely-cause order, and in a salt pool that order is slightly different from a chlorine pool because of the CYA relationship above.

Pages in this hub:

• Cloudy salt water pool: causes in order of likelihood
• Salt water pool gone green
• Algae in a salt pool

Cold water and the off season

Below roughly 60°F most generators reduce output and many stop entirely near 50°F, which produces low-salt and check-cell warnings at exactly the moment owners are opening the pool and already adding salt blind. One owner reported hitting 4,800 ppm in a 35,000 gallon pool “after adding six extra bags at spring opening.”

If you are opening a pool and the panel complains, note the water temperature before you believe it.

Pages in this hub:

• Winterising a salt water pool
• How to close a salt water pool for winter

Where to go next