Hot Tub Water Chemistry FAQ
Hot tub water chemistry can feel like a mix of science, routine maintenance, and a little bit of mystery. The questions below cover common water chemistry issues, including pH, alkalinity, sanitizers, foaming, cloudy water, scaling, odors, and chemical storage.
For a more complete overview, visit our Hot Tub Water Chemistry Guide. You can also visit our Online Knowledge Base for additional maintenance and replacement product information.
Common Hot Tub Water Chemistry Questions
Why do I need to correct my pH or alkalinity constantly?
Almost everything can cause pH and alkalinity levels to change. Spa usage can raise pH, while adding chlorine can lower it. Alkalinity can also change when fresh water is added to the spa.
Why is the pH level higher in my spa than in my pool or source water?
Warm water naturally tends to maintain a higher pH level than cooler water. Because hot tubs operate at higher temperatures than pools, pH behavior can be different.
Is it better for pH to read on the low or high side of 7.2 to 7.8?
Chlorine generally performs better at a lower pH range, around 7.2 to 7.5. Bromine works well throughout the broader 7.2 to 7.8 range.
What is the benefit of using potassium monopersulfate?
Potassium monopersulfate is a non-chlorine shock that helps oxidize contaminants. This can reduce sanitizer demand by allowing chlorine or bromine to focus more on sanitizing the water.
What is scaling in the water?
Scaling is a mineral buildup that can form on spa surfaces and internal components. It is often caused by high calcium, high pH, high alkalinity, high mineral content, or excessively high water temperature.
Will too much mineral agent hurt my spa or water chemistry?
Overusing most mineral agents usually will not affect water chemistry or harm the spa, but it is best to check the instructions from the manufacturer of the product you are using.
How often should I change my hot tub water?
A common guideline is every 90 days, but it depends on spa usage and how many chemicals have been added. If the water becomes oversaturated with total dissolved solids, chemicals may become less effective.
What causes foam in spa water?
Common causes include laundry soap residue on swimsuits, filter cartridge cleaner that was not fully rinsed, deodorant, body lotions, hair products, waiting too long to change the water, high pH, or poorly formulated chemicals.
What causes milky water and how do I correct it?
Untreated cloudy water can become milky water. Adding pH increaser to spa water with very low pH can also create a temporary cloudy reaction. A natural enzyme clarifier and a clean or new filter can often help.
Why do jets create a foul odor after the spa or jetted tub has not been used?
This is common in jetted bathtubs and some hot tubs because water can remain stagnant in the plumbing lines, allowing bacteria to grow. A jet-line cleaner can help clean the internal plumbing and reduce odor.
Do chemical products have a shelf life?
Most spa chemicals last well when kept in a temperature-controlled, dry environment. Liquid products that have frozen and granular products that have hardened should be disposed of according to the product instructions.