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Spa Chemical Start Up Guide

Balancing your spa chemicals after draining and refilling the water is an important step for many whose tap water is less than perfect. Doing it in the right order is even more important, to prevent problems, make adjustments, and balance something that takes just a few hours, not days.

Many of our customers have fill water that is very hard (or very soft), very acidic (or basic), and loaded with metals or metals, phosphates and nitrates, or silt and sediment. Not good spa water. Here's our 3 step process for refilling a spa, balancing the chemistry, and starting sanitization.

Pre-Filter the Water

City water often contains high levels of chloramines, ammonia and phosphates. If you have a DPD pool or spa test kit, test the water sometime, you may be surprised! Our Pre-Filter removes all types of chlorides and sulfides, minerals, metals and contaminants. Filters down to below 1 micron in size, it even softens hard, scaling water and removes odors! Just connect it to a garden hose and fill your spa. It's good for 3-4 fills before the filter clogs.

Balance the Water

Balance Total Alkalinity and pH before other spa chemicals

When balancing your spa chemicals, the first step is to test the water with a reliable test kit or test strips. Test kits are more accurate, but most people test the spa water with test strips.

Alkalinity first! Add Alkalinity Increaser first, to bump it up to around 100ppm. This helps hold your pH level steady when several hot tubbers jump in the water, so don't neglect your Total Alkalinity level.

Second is the pH adjustment. Add a pH decreaser (acid), to lower the pH to around 7.4, or between 7.3 and 7.5. A high pH can cause calcium scaling, and it also causes the sanitizer to work harder, and makes it easier for bacteria and other pathogenic stuff to grow. A low pH, below 7.2 is equally troublesome, and below 7.0, the water becomes acidic and can corrode finishes, damage wood, or harm sensitive spa components.

After adjusting Total Alkalinity and pH, let the spa circulate for about 10 minutes or so, and then adjust the Calcium Hardness. A range of 200-400 ppm keeps spa water from becoming aggressive in its desire for calcium, which can lead to corrosion and staining. Again, let the spa circulate for about 10 minutes before starting sanitation.

sanitize the water with chlorine

Sanitize the Water

Boost the bromides in the water by shaking in some Brom Booster, about two tablespoons. This is an important first step if you use bromine tablets in your hot tub. If you don't add sodium bromides, it can take days or weeks to build a bromine residual, which leaves your spa vulnerable to bacteria.

Immediately after the bromides are added, shock the spa with chlorine granules. After a refill, use a chlorine shock to kill anything in the fill water and to activate the bromides.

Keep the spa cover open for a few hours after shocking, to allow gas to escape. The spa is not ready for use yet, not until the sanitizer level has fallen below 5 ppm. Check and balance in the right order and you can make quick work of spa and hot tub start-ups!

Recommended Products

Spa & Hot Tub Chemicals


Leslie's - Chlor Brite Granular Chlorine Spa Shock


Spa Aromatherapy


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Leslie’s makes every effort to provide accurate recommendations based upon current ANSI/APSP/ICC-5 2011 (R2022) standards, but codes and regulations change, and Leslie’s assumes no liability for any omissions or errors in this article or the outcome of any project. You must always exercise reasonable caution, carefully read the label on all products, follow all product directions, follow any current codes and regulations that may apply, and consult with a licensed professional if in doubt about any procedures. Leslie’s assumes no legal responsibility for your reliance or interpretation of the data contained herein, and makes no representations or warranties of any kind concerning the quality, safety, or suitability of the information, whether express or implied, including, without limitation, any implied warranties of merchantability or fitness for a particular purpose.