Mixing MetalsDissimilar metals, when separated by

more than 0.2 volts in an electrolytic solution, may be susceptible

to galvanic corrosion. The least noble — or

corrosion-resistant — of the two metals will experience

oxidation and deterioration.
Mixing MetalsDissimilar metals, when separated by more than 0.2 volts in an electrolytic solution, may be susceptible to galvanic corrosion. The least noble — or corrosion-resistant — of the two metals will experience oxidation and deterioration.
  • Homeowners nationwide are embracing the convenience of salt pools, but these systems still need to be monitored by trained technicians.

The most common problem — increased scaling — requires chemical adjustments and old-fashioned elbow grease. In the meantime, a routine check of the salt cell will uncover most other snags.

Even less frequent byproducts of salt pools, such as corroded decks and equipment, come with relatively simple solutions. The key lies in knowing what you’re up against.

  • Scaling in the ECG

Salt-chlorinated pools are vulnerable to scale formation for two main reasons. First, in an electrolytic chlorine generator (ECG), electricity is created by a negative electrode called an anode and a positive electrode called a cathode; the chemical reactions around the cathode produce sodium hydroxide (a strong base) as a byproduct of the electrolytic chlorine generation process, and this leads to scaling on the cathode. Second, not all salt added to pools is 100 percent pure. Within the ECG, tiny chemical impurities in the salt can break down into byproducts, such as orthophosphates, which provide food for algae and can contribute to scaling. Many units come with indicator lights that notify you when it’s time to check the salt cell for excessive scaling. To rid the cell of calcium deposits, use a solution that’s one part acid and either two- or three parts water. Others may opt for a weaker solution. For heavy calcification, experts recommend spraying the cells with water from a hose, to dislodge any scale or debris. In the most extreme cases, multiple acid washes and an overnight soak may be necessary; but this practice risks damage to the cells, so use it only as a last resort.

  • Water balance

Weekly doses of muriatic acid are necessary to keep the water’s pH in balance, and to prevent surface scaling. A chelating agent also may help prevent calcium from coming out of solution. Cloudy water and scaling are telltale signs of high pH and TA levels. If you detect these symptoms, you’ll want to first return alkalinity to its proper range of 80- to 120 ppm. Add muriatic acid or sodium bisulfate to lower the total alkalinity. The higher the TA levels, the more difficult it becomes to change pH. Remember, pH greatly varies when TA is low. Once an ideal TA level has been reached, consider keeping an artificially low pH level of 7.2 to compensate for pH rise until your next service call. A regular dose of muriatic acid should keep pH and TA levels in check.

  • Calcium hardness

Ideal levels are between 200-400 ppm. Higher levels mean more calcium is likely leaving the solution, which will increase scaling — especially in the ECG. To lower the calcium levels, simply dilute the water.
Also, consider adding a chelating agent to combat high hardness. This chemical will bond to the calcium and keep it in solution, adding another layer of protection. However, if the pool is already showing calcium deposits, it’s probably time to deploy the brush.

  • Clean with care

Removing scale or salt residue is often a matter of preference. Some use abrasive media blasting, while others would rather brush with a muriatic acid solution. Either way, avoid causing damage to any rockwork around the pool. Tile soap can take the paint off of artificial rock, and even real rocks can become discolored with acid. When salt comes out of solution, the safest solution may simply be  brushing.

  • Low chlorine

Though a salt system requires minimal maintenance, keep in mind that it is often your sole source of sanitation on this type of pool, and produces a fixed amount of chlorine per day. If a cell becomes scaled and electrolysis fails to generate adequate chlorine levels, water chemistry suffers. What’s more, low chlorine readings could indicate a damaged unit or blown fuse. Thus, regular inspection and cleaning of  the salt cell, while relatively simple, are essential for effective maintenance. Still, some types of scaling, such as phosphate scale, are difficult to detect visually. That’s why it’s important to use an anti-scalant regularly.

  •  Clogged cells

Provided the pool doesn’t show exceedingly high hardness levels, the cell shouldn’t require cleaning more than once or twice a year. Consider adding a water softener as another preventive measure against calcification.

  • Low salt

If you don’t replace the pool’s salt, splash-out or backwashing eventually will lower your salinity levels. If salt levels drop too low, the generator may be unable to produce enough chlorine. Many units will indicate low salt levels, often when salinity dips below 2,500 ppm. When adding salt manually, pour it in the deep end of the pool, and  stir it with a brush to speed up the dissolution. Another technique involves dissolving the salt in a 5-gallon bucket of water, then pouring it in as you walk around the pool. 

  • Corrosion

Galvanic corrosion occurs when two dissimilar metals come into contact through an electrolyte solution, namely saltwater. Though rare, it is seen most often with high levels of total dissolved solids (TDS). The TDS level found in salt pools typically is three times greater than in vessels using traditional chlorine. Also, make sure any metal equipment can withstand higher salt levels.

  •  High TDS

Acceptable TDS in a traditionally sanitized pool is around 1,500 ppm or lower, depending on the type of fill water and the last time the pool was diluted. By contrast, the water in a salt-chlorinated pool contains 3,000- to 3,500 ppm of dissolved salt, in addition to the usual TDS of calcium and other metals. This combination can take the pool above 5,000 ppm of TDS, which is increasingly fertile territory for conductivity and galvanic corrosion.
As a general rule, dilute the pool water as soon as TDS levels exceed 1,500 over source or fill water. Most salt systems operate at a salinity level of 3,000 ppm, so consider dilution at TDS levels above 4,500 ppm. Fortunately, many salt systems include high-salt indicator lights and self-regulating mechanisms. When the unit detects excessive salinity, it shuts down automatically to avoid damaging the pool.

  • Salt check

Several systems display salt levels via a digital readout. However, these readings measure salt content by the amount of electrical conductivity of the water, and the water’s temperature. As a result, you’ll never learn the actual number of chloride ions present. Outside interference can affect the water’s conductivity and produce false readings, too. That’s why it’s encouraged to verify the system’s reading with an independent salinity test. You may also use a test strip, titration test or electronic meter for salt. 

  • Compatible equipment

Some products and equipment, such as aluminum tracks for an automatic pool cover system, perform poorly in high-salt conditions. Certain stainless steel filters also could be at risk because of galvanic corrosion. Check with the manufacturer to ensure each product is compatible with a salt pool.