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Hot Tub Chemicals: The Four Elements Of Spa Chemistry

There are so many joys to owning a hot tub, it’s difficult to count them. From romantic, late-night spa sessions to energizing morning soaks to family fun with games and light shows, your spa is a near-endless source of relaxation and entertainment.

But owning a hot tub isn’t all fun and games: In order to keep your water clear, clean, and inviting, you’ll need to do a little chemistry. Don’t worry: It’s easy once you know what to do. In fact, there are only four things you need to do to ensure that your water is healthy and balanced:

1. Alkalinity

What is it?

Alkalinity is what neutralizes the acids in your spa, and alkalinity that’s too high or too low can lead to a wide range of issues, from minor skin irritation to algae growth and cloudy water.

How do you test it?

Begin by dipping an alkalinity test strip into the hot tub water and then comparing the results to the color chart on the bottle or on the product insert. Your hot tub’s alkalinity level should be somewhere between 80 ppm and 120 ppm. If your alkalinity is too low, use an alkalinity increaser to get the levels right. If it’s too high, you may have an issue with calcium hardness and should call a professional for guidance.

2. PH

What is it?

When your PH levels are too high, other chemicals lose their effectiveness and that can lead to algae, scales on the spa, mineral buildup, and even eye irritation. When they’re too low, the water will corrode the metal components of your hot tub, reduce the efficiency of other chemicals, and could cause skin irritation.

How do you test it?

Use a PH test strip. Dip it into the spa water and compare it to the color chart that came with your test kit. You want your PH to be somewhere between 7.2 and 7.8. Levels below 7.2 mean your water is acidic and will need to be brought up. To reverse this, use a PH increaser to balance the water. If your PH is above 7.8, you can add a PH decreaser.

3. Sanitizer

Because spa waters stay consistently warm, some viruses and bacteria would love to make it a home, and that’s why your next step is to add sanitizers such as bromine or chlorine to your tub. Both types of sanitizers will do the job, but people tend to prefer one over the other:

  • Chlorine is relatively inexpensive and does a good job of removing contaminants, which makes it a popular choice among many spa owners. One potential drawback of chlorine, though, is that it has a high PH, so you’ll need to use a PH decreaser to keep things stable
  • Bromine is a little pricier than chlorine — but many hot tub owners prefer it because it’s super-effective at killing bacteria and it doesn’t affect things like PH or alkalinity.

4. Shock Treatment

What is it?

A shock treatment breaks down organic contaminants in your tub, preventing the development of cloudy water, algae, bacteria, and odors. You can choose between a chlorine shock and a shock oxidizer.

How do you test it?

A shock oxidizer is an oxygen-based shocker and is used for routine maintenance. A chlorine shock can help clear up, say, a sudden outbreak of algae or a persistent layer of film.

If your water is still cloudy after shocking it, it may be that your fill water has an excess amount of small particles in it. If so, you can use a spa water clarifier to clear it up. This works by coagulating the small particles so they can flow through the spa filter.