Chemicals for Hot Tub Start-Up

Video Tutorials

Once your spa is filled, the next step in the hot tub start up process is adding chemicals to your spa for the first time. In this episode of Master Spas TV, Shane will provide step-by-step, hot tub start up chemical instructions including how to test hot tub water, what chemicals to add to the hot tub, and the importance of adding chemicals in a specific order.

Before adding any chemicals to your hot tub, it is crucial that you carefully review the labels of the spa chemicals you will be using for dosing information. The amount of chemicals needed is based on the gallons of water your hot tub holds, you can find the gallon capacity in your owners manual.

If you haven't filled your hot tub yet, watch our "How to Fill a Hot Tub" video for easy to follow instructions and helpful hints for filling your spa that will make balancing your water chemistry easier.

Steps to Hot Tub Water Chemistry

First, we need to fill the tub if you need help you can check out our video where we walk through the initial fill-up process. Along with our video, you can find information about the initial fill-up in your owners manual and at

Once we've filled the hot tub, now it's time to check the chemical levels. Now it's important to note the quantities to apply can vary based on the size of your hot tub and the chemical concentration of the brand or product being used. You should know how many gallons of water your hot tub holds. This can be found on the model spec page in your owner's manual and make sure you familiarize yourself with the recommended amount for the chemicals you plan to use, these should be directly on the bottle.

The testing strips we're using test all necessary levels at once, but depending on your test strips you may need individual testers for pH alkalinity calcium hardness and chlorine. It will save time if you can have the following chemicals on hand:

  • a pH increaser
  • a pH decreaser
  • sodium-dichlor
  • chlorine granules

Keep in mind it matters in which order we balance our chemicals. First we need to adjust our pH level and total alkalinity. When we're retrieving a test strip make sure that we're not contaminating the remaining strips in the container and once we have the strip in hand simply follow the instructions on the packaging for dipping and discerning the results. Our goal is to find our pH between 7.4 and 7.6 and our alkalinity between 100-120 parts per million. Now my initial test indicated and my pH was a little low so referencing the information on the pH increaser, I know I need to add one capful of pH up to compensate for this low level. It's important that we balance our pH first before moving on to the next step adding a sanitizer if the pH is not balanced it can render the sanitizer ineffective remember when adding chemicals always spread them across the surface of the water with all the therapy pumps turned on.

And now we wait 30 to 60 minutes before retesting. We'll need to repeat this process until our alkalinity and pH levels are within the recommended ranges. And keep in mind that extremely high or low test results can take a while to get properly adjusted, keep working at it until your hot tub has reached the proper levels.

And next, we'll need to sanitize the water and the components of your hot tub. There are two primary types of sanitizers chlorine, which we have here, and bromine. Sodium-dichlor, chlorine granules are what we, at Master Spas specifically recommend for sanitation. They offer the best results with the features of your hot tub; such as the EcoPur and the ozone systems. And do not confuse this version of chlorine with tricor type chlorine tri chloric and damage the components of your hot tub.

However, if you are unable to use chlorine for personal reasons you may opt to use bromine. Bromine doesn't dissolve as quickly and therefore you must wait a little longer for proper testing of the waters levels. Also, bromine can build up over time if you have to use bromine just be careful not to over treat. Adding tablets to a floater or a dispensing device may sound easy, but you must continue to test the water and remove the tablets once a hot tub has reached the proper sanitation levels.

Now for our initial startup of our hot tub, we want our free chlorine levels to be higher than what is best for daily use to ensure for proper startup sanitation of the water and components. You should aim for a level around 5 to 8 parts per million. Wait an additional 30 to 60 minutes before re-checking the free- chlorine level, and do not allow anyone to get in the hot tub until the chlorine levels have dropped between 2 and 4 parts per million, which is a recommended range by the way. One last test and that's it. Once enough time is passed to allow the chlorine to fall to the recommended levels then your water is balanced and ready to enjoy.

For European countries, please refer to this Water Chemistry Guide for appropriate chemical levels per BS EN 17125:2018.