As you already know, keeping a balanced, healthy pool or hot tub takes a lot of careful work, maintenance, and at times, troubleshooting. But how often do you need to completely drain your pool and start clean? And how often should you drain your pool vs hot tub water?
How often should you drain commercial pool water?
Properly maintained commercial pools should only require draining and water replacement once annually. Most current pool pumps turn over pool water in 8 hours or less. Even if you see huge volumes of swimmers, the water in your pools is being cycled regularly and treated with chemicals so that it is safe, sanitized, and healthy to swim in. In cases where you are struggling with issues such as algae or calcium hardness, you still want to try to address this through chemicals and other measures first.
The risks of draining pool water
While there are a few reasons you may need to drain commercial pool water outside of annual replacements, first, we’re going to look at all the reasons why you want to avoid draining pool water more than necessary.
For starters, even small pools hold a large volume of water–and volumes of expensive chemicals. Completely draining them and starting over with fresh water and chemicals is expensive.
It’s also time-consuming–for some pools, draining and refilling water takes multiple days–and requires you to shut down your facility, which can lead to revenue loss.
Then there’s the fact that pools are designed to have water in them. If left for extended periods of time without water in them to hold them in place, the pool basin can shift, bow or crack, leading to structural damage. This is particularly true if your area has recently seen heavy rains, and the groundwater levels are high, as they can cause empty inground pools to lift out of the ground. This damage can also extend to the surfaces in place surrounding the pool, such as concrete.
Similarly, pool liners, fiberglass, and other pool materials aren’t designed to withstand direct sunlight, without water, in the peak of summer. They can be damaged both by the sunlight itself and by intense heat, leading to expensive repairs.
When and if you do need to drain your facility pools, even partially, it's best done when temperatures are below 85 degrees and in the evening hours when sunlight is less intense. For this reason, it’s also best done in spring or fall.
That said, there are a few additional instances–typically emergencies–where you’ll need to drain your pool water.
Emergencies that may require pools to be drained
- Glass in the pool: Glass in pools is particularly dangerous, as it's invisible underwater. Because it’s impossible to tell if you’ve removed all of it from the water, in the case of broken glass, you will need to drain the entire pool, sweep it, and vacuum it before refilling. The best defense against glass in the pool is a no glass policy, as beverage bottles are the number one culprit here. But there are still some cases, for example, a broken pool light bulb, where it’s unavoidable.
- Human waste: Even in the case of a poop incident, draining water is a last resort. Depending on if the waste is solid or diarrhea, you want to take the necessary steps to remove as much of it as you can, then test and remediate to ensure the water reaches the necessary Free Chlorine levels. However, because diarrhea is more difficult to remove and also the most common swimming-related disease outbreak, it may be necessary to drain the pool or hot tub as a last resort.
- High TDS Levels: High chemical use, as well as older pool water, can contribute to high total dissolved solids (TDS) levels in your pool. When these levels are high, it causes any chemicals you add to work harder to disperse, decreasing their disinfecting ability–which makes high TDS levels both a safety issue as well as operationally expensive. The only way to remediate this issue however is either to partially or completely drain and replace pool water.
Maintenance or pool repairs may also require you to drain pool water completely–for example, if you need to perform an acid wash to treat stains, repaint, or repair cracks. However, ideally, you’ll schedule these tasks and repairs during your annual drain and water replacement.
How often should you drain commercial hot tub water?
Commercial hot tubs and spas are a bit different than pools, and will require draining more frequently. Particularly if you see a high volume of guests, you will likely need to drain your commercial hot tub every couple of days in order to maintain healthy water. The CDC recommends commercial hot tubs and spas drain water on a weekly to monthly basis, depending on the usage and water quality status.
This is due to hot tubs’ lower water volume combined with high temperatures and “heavy bather loads,” which make continuous water quality more difficult to maintain.
Doing so ensures removal of Total Dissolved Solids (TDS) as well as harmful bacteria that can build up resistance to antibacterial chemicals. Contrary to pool maintenance, draining hot tubs more frequently is also often the preferable method to intense chemical shock treatments which can cause damage to hot tub seals and surfaces over time.
Not draining hot tub water frequently can lead to water contaminated with bacteria, algae, and other harmful microorganisms that can cause skin and eye irritation and disease. It can also cause unbalanced water, which leads to scaling and corrosion of hot tub parts, higher maintenance costs, shorter hot tub lifespan, and poor water quality.
- Hot tub water should be tested for pH and disinfectant levels at least twice per day–and hourly when in heavy use
- Water pH needs to be maintained between 7.0-7.9
- Free chlorine levels need to be maintained at 3-10 parts per million (ppm) continuously, or bromine levels at 4-8 ppm continuously
- Treat hot tubs with a biocidal shock treatment on a daily to weekly basis, depending on water quality status and how often you are draining and replacing water.
- Regularly inspect both hot tub surfaces and the accessible recirculation system components for slime, and clean to remove as needed.
- Cover the hot tub when not in use to both prevent disinfectant loss and contamination from dirt and debris
Other reasons to drain your hot tub water include high TDS levels, cloudy, discolored, or bad-smelling water, scale buildup, or guest complaints of skin irritation or itching. The emergency reasons to drain a hot tub are the same as for a pool: in the case of broken glass, or human waste incident, you may need to drain the hot tub water and fully replace it.
Key takeaways
Maintaining healthy pool water is a bit different than maintaining healthy hot tub water, however, both require regular testing, chemical adjustments, cleanliness, and care. Whether you need to avoid draining your commercial pool, or ensure your hot tub stays clean, it’s critical to use a testing system that’s accurate, documented, and Health Department compliant. This ensures your aquatic facility avoids costly mistakes, from health risks to your guests to chemical overuse.
PoolShark H2O’s simple app can do the complex pool math equations for you automatically, in seconds, making it simple to stay on top of your pool water quality, without overusing chemicals–which can be costly both for health and for your bottom line.
As a digital logbook, it locks pool chemical test results and adjustments, making them 100% Health Department compliant and alerting managers and owners when pools go untested for more than 24 hours or require attention.
In the case of those emergency situations, select the incident you’re managing and from there, the app automatically calculates the free chlorine adjustments needed–then digitally records and locks every test result and adjustment for you, so everything is maintained accurately throughout the entire process and after. Pool or hot tub managers, operators, and owners can access those records to ensure the incident was handled appropriately.