Dealing with Scaling and Staining

pool scaling

Stains and scale are two words often used together because they typically happen at the same time. Saturated pool water, choked with calcium and other minerals, can turn cloudy when normally dissolved solids come out of solution. When this happens, the calcium bonds rapidly with surrounding particles, attaching to your pool surface as an ugly scale stain or as a sheet of dirty calcium film.

It might start as just a simple error in pH levels or an innocent shocking of the pool. Next thing you know, the water is cloudy, or scaly pool stains appear days or weeks later.

For those of you battling waterline pool scale or all-over calcium film stains, do not despair. There is hope! Read on to learn how to deal with swimming pool scale and stains.

Step on the Pool Scale

Recent blogs on the topic of pool scale problems have popularized the notion of two types of pool scale. In actuality, there could be half a dozen types of calcium scale found in a pool. But in the majority of cases of calcium scale and stains, calcium carbonate is the culprit. Nearly every pool is susceptible to cloudy water, stains and scale deposits when not managed properly.

Calcium Carbonate – This type of scale often deposits a fine sheet of film over the entire pool, but can also produce stalagmite-like residue that builds up in layers. Calcium carbonate will scrape off easily and dissolves with muriatic acid or other strong acids. High calcium, minerals and total dissolved solids coming out of solution will cause pool scale. It can also come from moisture behind tile and raised walls, which leaches out as efflorescence.

Calcium Silicate – As the name suggests, this is calcium mixed with a form of sand. It creates sharp nodules and crystals as it is deposited on pool surfaces, and it’s sharp enough to abrade skin and snag swimsuits. This alarming result is often caused by high pH combined with high calcium levels. New pool plaster is susceptible to this during the first year, but you can fight back by carefully monitoring pH and alkalinity levels during the first summer and winter.

Pool Scale and Stain Removal

The easiest and best way to remove pool stains and scale from concrete, plaster and pebble pools may be to drain the pool and acid wash the surface. You could also have the tile line bead blasted. But if you’d rather save time, money and water, read on. For manageable amounts of pool calcium deposits, scale or stains, less drastic (and less expensive) solutions are available. The most popular methods of removing calcium or mineral scale and stains in pools include:

Pumice Stone – A pumice stone is a natural volcanic stone used on ceramic tile, concrete or plaster surfaces to rub away both types of scale. It’s effective and fun to use (it floats!). However, it wears thin quickly. When using a pumice stone, make sure to keep both the stone and the surface you are cleaning wet at all times to prevent scratching.

Stain Erasers – Stain erasers are made of softer abrasives that are effective on any pool type—even vinyl and fiberglass pools. They’re made for removing calcium scale at the water line or any other place in the pool. True to its name, the stain eraser will rub off stains and scale while you scrub, similar to a pencil eraser. Simply attach to a pool pole or use as a handheld pool stain scrubber.

Descale-It – Descale-It is a safe to use, bio-friendly pool stain removal chemical that works without harsh fumes or rough abrasives. Scrape off the big stuff first, then spray directly on pool scale and efflorescence. This powerful natural solvent dissolves calcium scale of all types. It is safe to use with all pool types and is also great for spas, sinks, tubs and showers.

Leslie’s Ultimate Scale and Stain Remover – This amazing stain removing chemical is safe for all surfaces to remove scale and stains from calcium carbonate. Better than a no-drain acid wash, this proprietary blend of polymers cleans and protects your pool without the use of acids or phosphates. It removes mineral film scale, waterline marks and scale stains in just weeks, but continues to work for months. Apply a maintenance dose every two weeks to a clean pool with good water balance. Leslie's Ultimate Scale and Stain Remover offers excellent summer and winter pool stain protection.

Pool Scale and Stain Prevention

There are specific ways you can prevent scale and stains (or scaly stains) in your own pool. This simple three-step pool stain and scale prevention program will keep your pool in top shape:

  1. Keep a clean pool to keep organic waste levels to a minimum. Bio matter in the pool, including algae, coagulates to form dirty stains during scaling events.
  2. Keep the pool water balanced with proper pH, alkalinity and calcium hardness levels. Maintain a constant and consistent chlorine level of 2-3 ppm at all times. This becomes more important with water temperatures above 70°F, as warmer water makes it easier for pool water to precipitate calcium scale.
  3. Add a maintenance dose of high quality sequestering agent every few weeks to maintain a residual level and keep the calcium locked in solution. Stain and scale chemicals naturally degrade in sunlight and should be replenished regularly.

Leslie’s Ultimate Scale and Stain Control – Our chemists took our popular Ultimate Scale and Stain Remover, mentioned above, and added a sequestering agent to control minerals and metals. Leslie’s Ultimate Scale and Stain Control keeps both locked in solution with strong molecular bonds. This powerful pool descaler even controls high levels of calcium and silicates while actively dissolving films and deposits. It’s a one-step proprietary blend of polymers to remove and prevent pool stains. Just apply every few weeks to a clean pool with good water balance, and our Ultimate Scale and Stain Control will do the rest.

Natural Chemistry Scale FreeScale Free is a powerful yet all-natural scale sequestering agent that creates strong bonds with mineral and metal ions, keeping them from coming out of solution. It works without resorting to acids or phosphates, just natural ‘chemical magnets.’ Scale Free stops mineral scale and metal stains by preventing calcium from precipitating and being deposited on pool surfaces. Regular use effectively prevents stains and scale buildup. Simply add one quart per 10,000 gallons for an initial treatment, then five ounces per 10,000 gallons each month to maintain the chemical lockdown.

For extra pool scale prevention, analyze your pool water with the Langelier Saturation Index to measure your pool water’s propensity to scale based on five known variables. The math is a bit complicated, but Pentair makes it easy with the Pentair LSI Calculator. For prevention of pool stains, stay on guard with high quality chemicals that you can rely on for control and removal of pool scale and stains. Add your own effort with good water balance and a clean pool, and you can stop the pool stain cycle.

If you are truly committed to a practically stain-free pool, follow these three guidelines to have the best chance of reducing the conditions where pool scale and stains can occur.

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If you have any questions about removing or preventing stain and scale, contact a local Leslie’s professional or visit

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