How Do I Clean a Salt Cell?

Pull the cell, look inside, and clean it only if you can see white crusty calcium scale bridging the plates. If the plates look clean and dark, put it back. Acid cleaning a cell that does not need it strips coating off the plates and shortens its life.

When cleaning is warranted, the standard solution is 4 parts water to 1 part muriatic acid, soaked for 10 to 15 minutes maximum, then rinsed well.

Safety first, and this part is not optional

Muriatic acid causes serious chemical burns and its fumes damage lungs and eyes.

• Work outdoors, upwind, never in a garage or enclosed space.
• Wear chemical splash goggles, acid resistant gloves and long sleeves.
• ALWAYS add acid to water, never water to acid. Reversing it can cause a violent exothermic splash.
• Never mix acid with chlorine, shock or any other pool chemical. That combination releases toxic chlorine gas.
• Keep a hose running nearby for immediate flushing.
• Have baking soda on hand to neutralize spills and the spent solution before disposal.

If any of that gives you pause, this is a reasonable job to hand to a technician.

Step by step

1. Turn off the pump at the breaker and shut the generator off. Close any valves isolating the cell.
2. Disconnect the cell cord from the control box, then loosen the unions on both ends and remove the cell.
3. Rinse the inside with a garden hose. A surprising amount of light debris and soft deposit comes off with water alone, and if the plates look clean afterward you are done.
4. If scale remains, cap one end with the cell’s cleaning cap or stand it upright in a bucket so it holds liquid.
5. Mix the solution in a plastic bucket. Pour in 4 parts water first, then slowly add 1 part muriatic acid.
6. Fill the cell with the solution until the plates are covered. Expect immediate foaming and fizzing.
7. Soak 10 to 15 minutes. When the fizzing stops, the acid has finished working. Do not leave it soaking longer hoping for a better result.
8. Pour the spent solution back into the bucket, neutralize with baking soda until it stops reacting, and dispose of it per local rules. Do not pour it into the pool.
9. Rinse the cell thoroughly with fresh water, inside and out.
10. Reinstall, hand tighten the unions with the O-rings seated and lightly lubricated, reconnect the cord, open valves, restore power and check for leaks.

Never scrape the plates

The plates are titanium with a thin catalytic coating, and that coating is the entire working surface of the cell. A screwdriver, wire brush or pressure washer will take it off and permanently reduce output. If a deposit will not dissolve in acid, it is not coming off safely.

A soft plastic tool can be used gently on the mouth of the cell for loose debris, but nothing rigid should touch the plate faces.

How often, and what scaling is telling you

Inspect every three to four months. Clean only as needed, which for many pools is once or twice a year and for some is never.

Frequent scaling is a chemistry problem, not a cell problem. Look at pH above 7.8, total alkalinity above 120 ppm, and calcium hardness above roughly 400 ppm. Fix the water and the cell stops crusting up. Many newer units have reverse polarity cycling that self-cleans to a degree, but it cannot overcome persistently unbalanced water.

Why cells scale faster in the Keys

Our fill water carries a healthy mineral load, and combined with year round evaporation in this heat, calcium concentrates in the pool steadily. There is no winter dilution and no seasonal shutdown, so the cell is under load twelve months a year and scale has more opportunity to build.

Add the pH climb that every salt system produces, and Keys pools drift into scaling conditions faster than pools in cooler, softer water regions. Checking the cell quarterly here is realistic, not excessive.

Look before you soak, because the cheapest cell cleaning is the one you correctly decided not to do.