Although pools and hot tubs both require sanitizers and balanced water chemistry, it’s important to remember how much the conditions in these bodies of water differ.
Many in the industry hold the misconception that pool and spa water can be managed and maintained similarly. This is true in broad terms: The correct amount of sanitizer residual must be maintained, water tested regularly, shock added to restore balance and help oxidation, and the filter cleaned on an ongoing basis. But that’s mostly where the similarities end. A spa should not be considered a small pool or treated as such.
To treat spa water correctly, service technicians should understand these differences and why they matter.
1. Master Your Hot Tub Chemistry
A hot tub is a much smaller body of water than a pool, so each bather can alter the water’s chemistry. And the higher temperatures create an environment for rapid bacteria growth, alter the rate at which sanitizer is processed, and even change certain chemical reactions.
Even the jets in a spa can change the water chemistry. When water shoots through the pipe and bubbles out of the jets, it causes carbon dioxide to evaporate. This loss increases pH and decreases alkalinity, potentially throwing off the chemical balance. The lack of carbon dioxide causes an increase in the formation of calcium. In hotter water, the solubility of calcium decreases, causing excess calcium to deposit as scale or to cloud the water. Scale build-up on heaters, jets, and spa plumbing can damage the equipment.
Higher water temperatures also cause hot tubs to more quickly burn through sanitizers, leaving chlorides and bromides that add to the water’s total dissolved solids.
To manage these dynamics, continuous sanitation with chlorine and bromine is the goal. Recommended sanitizer levels for spa water are 3 to 5 ppm for chlorine and 4 to 6 ppm for bromine. Additionally, pH levels should fall in the 7.4 to 7.6 range, alkalinity between 80 to 120, and calcium hardness between 200 and 400.
The mineral makeup of well water can have even more impact on the chemistry in spas, says Mike Peacock, owner of Atlanta-based CES Services. Sanitation formulas may need to be specialized for some areas.
When choosing sanitizers, technicians must consider how they will respond to the special conditions of a spa. For instance, some pros avoid stick chlorine, worrying that the very low pH in this form will drive the pH out of normal range in the small body of water.
Foaming poses another unique issue for spas. Contaminants from bathers, such as lotions and soaps, create foam when mixed with aerated water. The wrong type of algaecide can also create foam. In spas, techs should avoid foaming algaecides.
2. Increase Safety Inspections
Regular safety checks in spas should be done at each service visit, and go beyond chemistry checks. Check drain covers to make sure they’re intact.
“Safety is much more critical in spas,” says Howard Weiss, a Certified Pool Operator instructor and general manager with Gaithersburg, Md.-based Contemporary Watercrafters. “We have a lot of spas out there without proper VGB covers.”
Some parents allow their children to play in their hot tubs, Weiss says. A child is more likely to come in contact with a drain cover in a spa than a pool because it’s so shallow. This could become an incredibly dangerous situation if drain covers are damaged, missing or otherwise not VBG compliant. Homeowners should be educated about these safety precautions.
Professionals also should check to make sure that all jets are open and the water is circulating properly. Jets and diverter valves that are blocked or closed create areas for bacteria to thrive.
3. Learn Manufacturer Differences
Years ago, spas had similar parts and systems, no matter the brand. But most of today’s models use proprietary components.
Manufacturers also have responded to consumer demand by developing ways to reduce chemical usage, with some incorporating UV, mineral sticks or other proprietary systems.
Often, these systems determine the correct formula for sanitizer use. “It’s important for service techs to be current on some of the alternative sanitizers that are becoming popular,” says Jeff Brooks, retail sales manager at Seattle-based Aqua Quip.
4. STEP UP Water Changes
Unlike pools, spas need their water replaced regularly — not just when the pH has gone beyond restoration. In addition to regular testing, techs should know when to dump and start fresh.
There is a formula to determine when the tub should be drained and the water replaced. Weiss says the replacement interval in days is equal to spa gallons divided by three, divided by the average number of users per day. So, if there are three users per day in a 300-gallon spa, the water should be replaced every 33 days.
5. Clean Components MORE FREQUENTLY
Some spa parts need more maintenance than their pool counterparts.
Filter cartridges clog much faster in spas, because more body oils are released as bathers sweat. Because of this, cartridges must be chemically cleaned with a filter-cleaning formula on regular weekly service visits, says Weiss.
Buildup and bacteria also can thrive in the pipes. Brooks recommends using a liquid formula designed to clean pipes that can’t be accessed — often called a purge product — to clean plumbing lines before emptying the spa. This reduces biofilm and scale buildup, which can flake out into the hot tub.
