In Hot Water Spas

May 30, 2014

In Hot Water Spas

Saltwater systems have flooded the marketplace as an alternative or natural way to sanitize your hot tub. However, is it really better? Let’s take a closer look at salt systems so you can make the best decision for your hot tub lifestyle.


Salt water pool systems were developed around 1980. Originating in New Zealand, the use of electrolysis to convert salt (sodium chloride or sodium bromide) to chlorine or bromine requires electrostatically charged plates or electrodes to convert the sodium to a sanitizer. Stated another way Sanitizing generators for the swimming pool environment are a solution for homeowners who struggle with managing granular chlorine dosing and other chemical additives. While salt generation systems may work for pools there are a few reasons sanitizing generators, either chlorine or bromine, may not be as good a fit for hot tubs.

Differences Matter

Factor in the following differences for a hot tub from a large, cool body of water such as a backyard pool:

  1. Hot tubs are much smaller than a pool, typically 400 gallons.
  2. Hot tubs have very warm water, up to 104⁰F.
  3. A hot tub is covered, it does not allow chemicals to vent, no UV from sunlight.
  4. A hot tub has metal components such as heaters, heater elements and jet face escutcheons which will corrode.
  5. A hot tub has more people and less water; which means faster consumption of sanitizer.
  6. A hot tub cannot tolerate calcium build-up which can be a by-product of sodium.

All these differences matter. A smaller amount of water does require less amounts of any sanitizer. So pool and hot tub water maintenance is not the same challenge. Most hot tubs today are equipped with ozone generators, which can mean even less chlorine or bromine usage to properly sanitize. When you add a mineral cartridge to soften water, you have a perfect combination creating soft, heated, sanitized water. However, if instead, you use a salt system in this higher temperature environment and add bathers, it is quite possible these types of generators may not produce enough chemicals to sanitize properly. Some salt system manufacturers even admit you may have to add additional sanitizer to maintain the water properly. At the same time, should the generator continue to run and sanitize without bathers (who ‘consume’ sanitizer) for a period of time, it may over-produce sanitizer. Over chlorination may lead to chemical gasses trapped under the cover, corroding exposed metals. Close extra attention must be paid to balancing water with salt systems.

When metal components such as heaters, heater elements, jet escutcheons (the metal rings around the jets) are exposed to high sodium doses (either sodium bromide or sodium chloride) corrosion may also occur. Just ask anyone living near the ocean about rust issues with metals, or areas in which highways are “salted”. Salt will attack and break down metals, causing rust and corrosion if exposed to metal. In addition, calcium build-up is a by-product of salt generating systems. Calcium results in hard water spots and build-up on internal spa components.

Warranty or Chemical Abuse?

Although there are many “aftermarket” and manufacturer installed sanitizing generators, it’s best to check with the manufacturers what will and will not be covered under warranty. Some manufacturers will decline warranty over an aftermarket addition of a non-manufacturer installed salt sanitizing unit. Often any corroded heaters or elements are not covered and the damage is attributed to “chemical abuse” due to over chlorination and calcium build-up. This can result in costly repair bills. When salt is added to the water, it is not immediately converted or electrolyzed to chlorine, it resides in the water. While many salt system manufacturers claim the amount of salt is at a minimal level, about 1500 parts per million of salt is required for these systems to work, which can be triple the amount of salt in tap water.

Maintenance, What Maintenance?

For something that is supposed to make sanitizing a hot tub easy, you cannot forget about maintaining this “timesaver”. Key factors to keeping the salt system electrostatically charged plates free of debris require a soak in mild acid; the plates or electrodes are not self-cleaning. Maintenance schedules suggest you clean the electrodes or plates in a mild acid solution, every 90 days. Certainly having to remove the electrodes from an electrical component in your hot tub and soak them for a specified time until the calcium build up is dissolved cannot be considered a “no maintenance” system.

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