Hot Tub Water Chemistry in 10 Minutes

Hot Tub Water Chemistry in 10 Minutes

Possibly the biggest learning curve for new hot tub owners is water chemistry. In this article, we'll break down the essentials in under 10 minutes; by the end, you'll understand what your spa needs and why. These also apply to all-season pools.

This article aims to help you understand water care but doesn't go into a specific care routine - for that, you can check out our free downloadable water care card.

Why do we need to add chemicals to the water?

Unlike a bathtub, hot tubs and other spas stay filled all the time. Without treatment, this water would develop bacteria and algae rather quickly.

The Big 4

There are 4 essential chemicals/measurements for spa water.

1. Sanitizer

The most important chemical, sanitizer is used to kill bacteria. If your sanitizer falls too low your water will develop bacteria and algae, and if it gets too high it can irritate your skin and damage your hot tub.

When it comes to sanitizing your hot tub, there are two options deemed safe by Health Canada: chlorine and bromine.

  • Chlorine

    • Pros:
      • Less expensive
      • More effective outdoors
      • Widely available
    • Cons:
        • Shorter lasting
        • Harder on skin*
        • More likely to smell*
      Note: these last 2 points are common misconceptions. Skin irritation is usually due to low pH (more below). The chlorine smell most of us are familiar with is usually due to low chlorine and organic contaminants: body oils, cosmetics, etc. (more below).
  • Bromine

    • Pros:
      • Longer lasting
      • Less likely to smell*
    • Cons:
      • More expensive
      • Less effective outdoors
      • Harder to wash off skin

We recommend chlorine because it's less expensive and better suited for outdoors due to it's UV resistance. Bromine can be a good alternative if you have concerns with chlorine sensitivity, but keep the above misconceptions in mind.

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Jacuzzi Chlorinating Granules - Hot Tub Store
Jacuzzi Chlorinating Granules
from $22.95 $41.25
Tip: Download the AquaChek Smart app to make water balancing a breeze. Know "what" and "how much" based on your strip colours. Sanitize your hot tub with Jacuzzi Chlorinating Granules Jacuzzi Brand Chlorinating Granules is a stabilized chlorine for your spa that provides effective sanitation as a soluble, quick-dissolving oxidation treatment. Promoting water clarity, eliminating odours and organic waste such as body oils and cosmetic products. This powerful sanitizer is fast dissolving and can be used for both regular daily chlorination as well as super chlorination. Chlorine will not affect pH or total alkalinity nor will it promote scale build-up. The chlorine level in your spa should be maintained between 1-5 ppm. Ideal spa pH: 7.2-7.8 Ideal spa Alkalinity: 100 - 160 ppm  Size: 1.5 kg or 720g Click here for Safety Data Sheet (SDS)
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Jacuzzi Bromine Tablets - Hot Tub Store
Jacuzzi Bromine Tablets
from $38.95 $79.99
Sanitize your spa with Jacuzzi Brominating Tabs Jacuzzi Bromine Tabs provide effective sanitation as a soluble oxidation treatment. Promoting water clarity, eliminating odours and organic waste such as body oils and cosmetic products.   Jacuzzi Brominating Tabs should be used with Spa Shock on a weekly basis to maintain effective levels of sanitizer in your spa. Bromine Tabs require water flow to dissolve and should be placed in a floating dispenser and should not make direct contact with the spa or bleaching can occur. Bromine is an alternative for Chlorine and can be used over a wider range of pH levels making it more forgiving in balancing water chemistry.    The bromine level in your spa should be maintained between 3-5 ppm. Ideal spa pH: 7.2-7.8 Ideal spa Alkalinity: 100 - 150 ppm  Weight: 1.5 kg Click here for Safety Data Sheet (SDS)
Jacuzzi Brominating Granules 700 g - Hot Tub Store
Jacuzzi Brominating Granules 700 g
$29.95
Sanitize your hot tub with Jacuzzi brand brominating granules. Jacuzzi Brand Brominating Granules provide effective sanitation as a soluble, quick-dissolving oxidation treatment. Promoting water clarity, eliminating odours and organic waste such as body oils and cosmetic products.   Bromine is an alternative for Chlorine and can be used over a wider range of pH levels making it more forgiving in balancing water chemistry.    Each capful holds approximately 18 g of Brominating Granules. The bromine level in your spa should be maintained between 3-5 ppm. Ideal spa pH: 7.2-7.8 Ideal spa Alkalinity: 100 - 150 ppm  Size: 700 g    Click here for Safety Data Sheet (SDS)

Although chlorine and bromine serve the same purpose, they should not be used interchangeably. If you'd like to switch from one to the other, you must complete a drain and fill.

2. Shock (Oxidizer)

Sanitizers are great at killing bacteria but struggle to break down organic contaminants like body oils, cosmetics, etc.

Oxidizer, most often referred to as "shock," breaks down these contaminants. As previously noted, it's actually sanitizer (particularly chlorine) interaction with these organic contaminants that causes the "chlorine smell." Shock helps prevent this.

Shock isn't measured on test strips; it just serves as an aid for sanitizer.

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Jacuzzi Spa Shock - Hot Tub Store
Jacuzzi Spa Shock
from $23.95 $63.00
Tip: Download the AquaChek Smart app to make water balancing a breeze. Know "what" and "how much" based on your strip colours.   Jacuzzi Spa Shock removes non-living organics and other contaminants from your hot tub without adding stabilizer, chloramines (which makes that "chlorine" smell) and frees up the chlorine to attack bacteria for a hot tub that is extra clean. More than that, Jacuzzi Spa Shock instantly gets rid of chloramines to make chlorine more effective and your tub smell and feel fresher. Using Jacuzzi Spa Shock will lower the amount of chlorine you use in your hot tub. Spa Shock is used in combination with your choice of sanitizer (bromine or chlorine) to restore water quality and boost sanitizer levels. For the most effective use, add after every use of the hot tub and only add chlorine as needed (when levels drop below 3ppm). For best results, add Jacuzzi Spa Shock before adding chlorine. First, add Spa Shock and run the jets with the cover open for 20-minutes. Then add chlorine and run your jets for 20-minutes with the cover open.     Size: 1 kg or 3kg Click here for Safety Data Sheet (SDS)

3. pH

pH measures the acidity of water. If your pH levels are low, your water is acidic, which causes skin and eye irritation and corrosion. If your pH levels are high, your water is basic which can lead to scale formation and reduced sanitizer effectiveness.

You adjust your hot tubs's pH using a pH increaser or pH decreaser.

Jacuzzi pH Up 750 g - Hot Tub Store
Jacuzzi pH Up 750 g
$9.95
Raise your pH with Jacuzzi pH UP.  Maintain a pH level of between 7.2 - 7.8 Size: 750 g
Jacuzzi pH Down 1 kg - Hot Tub Store
Jacuzzi pH Down 1 kg
$9.95
Reduce your pH and alkalinity with Jacuzzi pH Down. Maintain a pH level of between 7.2 - 7.8 for safe and clean water.  Size: 1 kg  Click here for Safety Data Sheet (SDS)

4. Alkalinity

Alkalinity measures pH stability - the water's ability to resist changes in pH. If it's too low, pH won't stay balanced; if too high, it becomes difficult to adjust.

You adjust your hot tubs alkalinity using an alkalinity increaser or a pH decreaser ("alkalinity decreaser" doesn't exist, but it would be the same thing chemically).

Jacuzzi Alka Up 750 g - Hot Tub Store
Jacuzzi Alka Up 750 g
$9.95
Raise your Alkalinity with Jacuzzi Brand Alka Up Alka-Up will prevent erratic changes in the pH level of your spa water while helping the bromine or chlorine work more efficiently.  Alka-Up also raises the total alkalinity of your spa water, while preventing any corrosion that can be caused by low alkalinity. It is a completely soluble powder that is broadcast into the water as needed. Test regularly and adjust, especially when fresh water is added. The ideal level of total alkalinity is between 80-120 ppm. Total alkalinity should always be balanced before adjusting pH levels. One capful holds approximately 25 g.  Size: 750 g  Click here for Safety Data Sheet (SDS)

Other Important Measurements

These don't need to be monitored as closely as sanitizer, pH and alkalinity, but they're important to keep in mind.

Stabilizer (chlorine only)

If you're using chlorine your test strips will also have a measurement for stabilizer (chemical name cyanuric acid) - this is added to chlorine to protect it from the sun's UV rays.

As you add chlorine over time, your stabilizer will increase; once it gets too high, chlorine becomes ineffective. The only way to fix this is to replace the water - one of the reasons a drain and fill 3-4 times a year is important.

Calcium Hardness

If you fill your spa with water that's too soft, it can lead to corrosion; if it's too hard, it can lead to scale buildup. Both can damage to your hot tub.

You can increase the hardness of your water with a calcium increaser, but the only way to decrease the hardness is by diluting with freshwater.

Most people using hard water use a stain & scale control product that prevents calcium and mineral scale buildup in the hot tub.

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Jacuzzi Stain and Scale 500 ml - Hot Tub Store
Jacuzzi Stain and Scale 500 ml
from $17.95 $50.85
Protect your hot tub or spa from unsightly stains, scale formation, hard water, and rust with Jacuzzi Stain & Scale Control. This powerful formula keeps your shell and equipment looking pristine, ensuring a long-lasting and enjoyable spa experience. Prevents stains, scale, and rust formation on hot tub surfaces Prevents damage from hard water Prolongs the lifespan of your spa equipment Maintains the visual appeal of your hot tub or spa Features: Effective stain and scale control formula Protects against hard water, minerals, and rust Easy to use and apply Size: 500 ml Directions: Add 1 capful of Jacuzzi Stain and Scale Control to your spa weekly When changing the spa water, add 2 capfuls for thorough protection   Click here for Safety Data Sheet (SDS)

Key Takeaways

The 2 most essential measurements for your spa are its sanitizer level and pH. Shock helps improve sanitizer effectiveness and smell (but isn't measured), and alkalinity shows how stable the pH is.

The goal of this article is to emphasize the essentials listed above, but if you're interested in a more complete chemical list, continue reading a bit further.

Other Popular Chemicals

Filter Cleaner

Giving your filter a regular clean is important to extending its life and preserving clean water - a filter cleaner does just that.

Jacuzzi Cartridge Cleaner - Hot Tub Store
Jacuzzi Cartridge Cleaner
$15.95
Increase the life span of your filter with Jacuzzi Cartridge Cleaner Jacuzzi Cartridge Cleaner's twin action is uniquely formulated not only to remove scale but to break down body oils, suntan lotion and grease that build upon the filters. Regular use of Jacuzzi Cartridge Cleaner, plus the use of a Zorbie will assure proper filtration of the spa water.  Size: 1 L   Product Instructions: Rinse the dirty cartridge with clean water to remove loose hair and debris. Add 500 mL (half the bottle) of Cartridge Cleaner to 10 litres of warm water in a PLASTIC pail. Remember to always add chemicals to water (and NEVER water to chemicals). Place cartridge in the cleaning solution and allow to soak for 12 hours. Remove the clean cartridge and rinse thoroughly with clean water.   Click here for Safety Data Sheet (SDS)
Aqua Magic Cartridge Cleaner - Hot Tub Store
Aqua Magic Cartridge Cleaner
$19.95
Aqua Magic Cartridge Cleaner is a powerful cartridge cleaner that eliminates the need for overnight filter baths! Simply spray on and wash off - no more fussing with filter baths, just spray, rinse and then reinsert into your pool cartridge filter or spa. 650ml   Click here for Safety Data Sheet (SDS)

Conditioner

Improves the smell and feel of your water. Some products like Jacuzzi Ultra-Spa also boost chemical effectiveness.

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Jacuzzi Ultra Spa Conditioner 800 g - Hot Tub Store
Jacuzzi Ultra Spa Conditioner 800 g
from $18.95 $56.85
Keep your hot tub smelling clean and maximize the effectiveness of your chemicals with Ultra Spa Water Conditioner. For ultra-soft spa and fresh smelling water add Jacuzzi Ultra Spa in addition to regular sanitizers.  Continued use will make maintaining pH and alkalinity levels easier. Size: 800g  Click here for Safety Data Sheet (SDS)

Mineral Cartridge

A natural sanitizer that can reduce the amount of chlorine/bromine needed.

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Nature2 Spa Stick - Hot Tub Store
Nature2 Spa Stick
from $49.95 $149.85
Description Nature2 Spa Stick works with your spa filter to give you clean, clear water with less hassle. Details Nature2 SPA is perfect for spa owners looking for an eco-friendly, low maintenance solution for keeping their spa clean and clear. Nature2 SPA uses a mineral bed technology that works with your Health Canada approved sanitizer to effectively control bacteria. Nature2 SPA works by automatically dissolving trace amounts of mineral elements into the water. Those elements act as a clarifier to help keep your water clean, clear, and scum-free. Just drop the Nature2 SPA stick into the spa's filter and forget about it for up to four months! Eco-friendly way to remove organics, irritants, and metals. Eliminates chemical odours. Low maintenance; lasts up to four months. Directions The Nature2 Stick sits inside your spa filter, resting in/on the filter pipe. It is very important this pipe is not obstructed. Spa models like the Jacuzzi J-300, J-400 and J-500 series have a grated pipe to prevent this. Assemble Nature2 Stick to needed length - when placed in filter it should sit near top Remove top of filter Place Nature2 Stick inside filter Put top of filter back on
ProClear Spa Sanitizer for Jacuzzi® Brand Hot Tubs - Hot Tub Store
ProClear Spa Sanitizer for Jacuzzi® Brand Hot Tubs
from $49.95
The ProClear Spa Sanitizer delivers a more efficiently sanitized, easily maintained, and odour-free hot tub. ProClear also significantly improves the look and feel of your water by providing a more consistent PH balance. Using trace elements of silver, ProClear kills bacteria more effectively than chlorine alone. It does this through an interaction with your regular dose of spa shock. When the special mixture of silver and minerals come in contact with MPS Spa Shock, a mild sanitizer is released into your spas water. This lowers the demand for chlorine and your spa water is not only brilliantly clear and soft but gives you an alternative to chlorine-intensive treatments. Use in conjunction with the CLEARRAY Water Purification System for clean, clear water. Reduces chlorine demand and requirement by up to 50% Naturally softens water Prevents pH bounce and helps stabilize your water's pH Requires weekly dose of sanitizer Requires Spa Frog Mineral Sanitizer in place of the ProClear Minerals. Compatible with Jacuzzi® J-500, J-400, J-LX & J-300 collection hot tubs. 

Enzymes

Another natural sanitizer that can reduce the amount of chlorine/bromine needed. Enzymes also condition the water, usually giving a "softer" feel.

Spa Solution - Hot Tub Store
Spa Solution
from $54.95
Spa Solution is a proprietary enzyme-based spa conditioning formula. Reduce the effects of harsh chemical additives in your spa. No more skin or eye irritation, rashes, or allergic reaction to spa use. Simply apply once every three months and enjoy your spa! This product is so safe, it requires no warning labels! So easy to use. Pour it in your spa and forget about it. Water so clean and clear you won't need to shower after using your spa. Never again suffer from burning eyes, dried skin, and irritating rashes. Reduce your dependency on harmful chemical additives. No more time-consuming water balancing and chemical adjusting. So economical- A purchase can last three months. 100% Non-toxic to all living creatures.
Waters Choice Pure Enzymes for Spas (monthly) - Hot Tub Store
Waters Choice Pure Enzymes for Spas (monthly)
$24.99
Description Waters Choice Pure Enzymes for Spas reduces the need for chlorine or bromine in your spa. Organics like sunscreen, sweat, and outdoor debris put a high demand on chlorine and bromine; this demand increases over time, causing greater chlorine or bromine use. Waters Choice Spa Enzymes break down organics in your hot tub, which frees up chlorine or bromine, allowing you to use less. The 12oz Pure Enzymes for Spas bottle is good for 1 month per 500 gallons (about 1900L); simply add a bottle each month. Directions: Clean your filters (for best results) Check if water is balanced - adjust if necessary Add 1 full bottle of Pure Enzymes 12oz each month (for spas up to 500 gallons) OR Add 1 full bottle every 3 weeks or 1 1/4 bottles each month (for spas over 500 gallons)

Foam Control

When organic contaminants and detergents (usually from bathing suits) are introduced into the water, it often leads to foam. A quick shower before you enter can help reduce this, but if you're still having issues, there are a couple of options.

The most popular solution is a special sponge that absorbs the contaminants - Zorbie is the most popular.

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Zorbie - Hot Tub Store
Zorbie
from $23.95 $72.00
The original Zorbie does a great job absorbing body oils, suntan lotions, make-up, dirt grime and lots of other stuff that gets into your hot tub water.  PLUS, due to its unique ion exchange capability, Zorbie also helps reduce spa & hot tub odours! Zorbie's tried & true flow-through action lets water pass right through while trapping odours & oils while absorbing about 20 times its own weight in unfilterable debris! Just throw it in the spa (best when used near the filter).  The more stuff it absorbs, the heavier it gets and sinks.  When it's really dirty & sinking, simply throw it away. Lasts 30 to 90 days. DO NOT SQUEEZE OR WRING OUT!
ScumRay - Twin Pack - Hot Tub Store
ScumRay - Twin Pack
$43.95

If you're in a pinch and need to clear up foam fast, there are also defoamer products - they won't treat the underlying issue though.

Jacuzzi Defoamer 500 ml - Hot Tub Store
Jacuzzi Defoamer 500 ml
$14.95
Jacuzzi Defoamer eliminates and prevents foaming in your spa. Hot tub foam accumulates on the surface of the water, which makes for a thick and unhygienic nuisance. You can prevent the buildup of foam by using the best spa defoamer. Jacuzzi Defoamer is a chemical solution that prevents the water from developing the layer of foam. Size: 500 ml   Click here for Safety Data Sheet (SDS)

Next Reading

When you're ready to dive a bit deeper into the specifics, we recommend checking out our free downloadable water care card.

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