What does a Dirty Salt Cell Look Like?

A dirty salt cell has white, crusty deposits on the plates and in the narrow gaps between them. On a badly scaled cell that crust bridges the gaps, so you cannot see light through the channels when you hold the cell up and look down them. A cell in good shape shows evenly colored plates with channels that stay open end to end. A thin film, or a dull and slightly uneven tone on the metal, is normal and is not a reason to reach for acid.

What a healthy cell looks like

With the cell out of the plumbing and drained, look straight down the channels between the plates. Not at the outside of the housing. The housing tells you almost nothing, and on cells with a clear body it can look cloudy from the outside while the plates are fine.

On a healthy cell the plates are smooth, the color runs evenly along each blade, and every channel is clear from one end to the other. Light passes through the stack. A hose rinse carries off anything loose and nothing is left behind that you can catch a fingernail on.

Plate color varies between cells and over time. Some read dark gray, some look almost black, some have a slight sheen. Color on its own is not a fault. What you are judging is texture and blockage.

What a scaled cell looks like

Scale is white to off white and it has grit. It builds as a crust on the faces of the plates and creeps inward from the edges until the channels start to close up. A badly scaled cell looks like the inside of a kettle in hard water country, and you can usually feel it before you can measure it.

It rarely sits in a tidy pattern. Orenda’s account of the mechanism is that scale forms on the cathode side of each blade during electrolysis, and since the unit reverses its own polarity on a cycle, every blade takes a turn as the cathode. So expect deposits spread across the stack rather than neatly on one face.

There is a second tell that is nowhere near the cell. When polarity reversal fractures that buildup, it releases into the pool as white flakes. Flakes collecting in the skimmer basket or sliding along the floor after the system runs are a good reason to pull the cell and look at it.

Scale, film, or just discoloration

The line that matters most is the second one against the first. A film that rinses off is what a working cell looks like after it has been working. Crust that stays put after a hose, and that you can feel, is the thing acid is for.

The panel often tells you before your eyes do

A salt chlorine generator has no salt sensor. It pushes current across the plates, measures how easily that current crosses, and turns the answer into a salinity number with a temperature correction applied. Scale is an insulator sitting between the water and the metal. Put enough of it on the plates and current crosses less easily, so the display reports low salt while the salt in the pool has not moved at all.

That is why a low salt message deserves to be treated as a question. Poolside’s troubleshooting guide puts it plainly: a LOW SALT warning is frequently not low salt, and scale, cold water, low flow and cell age all produce the same words on the screen. Orenda gets to the same place from the physics: the cell measures conductivity, not salt, and cold water conducts less, so the panel reads low in cool weather while nothing in the water has changed.

So the order of operations runs backward from what most people do. Get an independent salt reading first. Our pool salt calculator is only useful once you have a number you trust, and salt levels covers what that number should be. If your test and the panel disagree, test the salt cell and check whether it wants calibrating before you open a bag of salt. A reading that dropped with no salt leaving the pool has an explanation, and scale on the plates is near the top of the list.

A worn cell and a dirty cell do not look alike, and that is the problem

Scale you can see. Wear you generally cannot.

Cells have a service life, and River Pools covers what to expect from one. An aging cell presents much like a dirty one from the deck: weak chlorine, a low salt message, output that will not hold where you set it. Poolside lists cell age next to scale as a cause of the same warning.

None of our sources publishes a way to look at a set of plates and judge how much life is left in them, and we are not going to invent one. A cell close to the end can look clean. That is the honest answer to a question people ask a lot.

What follows from it is practical. Acid dissolves scale. It does not put anything back on a plate that has worn. If the cell comes out looking clean, gets soaked anyway, and still will not hold output, the next question is age, not another soak. Our page on how long does a salt cell last sets the expectation, and salt cell replacement covers what to do when the answer is that it is finished. This is the single most common way an inspection goes wrong: a cell that is simply old gets acid cleaned every few weeks all season.

What not to do while the cell is out

Do not scrape the plates. Not with a screwdriver, not with a wire brush, not with anything metal. In The Swim is explicit about it in its winterizing steps: never use metal to scrape the generator plates. The plates are coated, and a scratch is permanent in a way scale is not.

Start with water. A hose rinse removes what is loose and shows you whether what remains is actually bonded to the metal. If it is, the acid step, the mix and the fill level all live on our page for how to clean salt cell. We have deliberately not repeated the procedure here, because identifying the problem and fixing it are two different jobs and people get hurt rushing the second one.

If you are still not sure what you are looking at

If the plates look fine, the water tests fine, and the unit still will not make chlorine, the fault may not be the cell at all. Flow, temperature and wiring all sit between the panel and the plates. Start with salt cell not producing chlorine, and if the whole system is new to you, our overview of the salt cell for pool explains what the thing is doing in the first place. Everything in this hub is indexed on the salt cell page, and how we test explains how we check what we publish.

Where to go next