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The ABCs
of Spa Water Chemistry
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By keeping in mind the basic ABCs of spa water chemistry, you'll be assured a pleasant and healthy hot tubbing experience for yourself, your family and friends. If you are new to the wonderful world of hot tubs, start here!

Although similar in one way to bath tubs, hot tub spas are not drained after each use, so we must take measures to ensure clear, clean, sparkling water. This means balancing the chemical properties of our spa water so that it is neither too alkaline nor too acidic. It also means maintaining a sanitizing system to keep the water healthy and free of harmful microorganisms.

After reading this section, go to Preparation & Maintenance for complete directions.

Sanitizers purify spa water

Always maintain your sanitizer.

The warm water of hot tubs would provide an ideal breeding ground for potentially harmful microorganisms if we did not initiate and maintain an effective sanitizer system to control them. Bacteria from our bodies, as well as airborne mold spores, algae, and even viruses can find their way into the water.

Fortunately, we have great sanitizer systems such as: Bromine, Cleanwater Blue, and Nature2 that can effectively destroy these microorganisms and keep the spa water safe and healthy.

Shock oxidizes contaminants

Be certain to shock treat.

Shock treatment is simply the routine of applying a compound to your spa water which oxidizes or breaks-down the dead organic material left behind from your sanitizer system, as well as non-filterable material such as dirt, soap films, hair spray and perspiration. Allowed to remain in the water, these contaminants provide a food source for bacteria and algae. Regular shock treatments eliminate them and the organics on which bacteria feed.

Regardless of which sanitizer system you use, periodic shocking is essential for clear, clean hot tub water. It will also allow your sanitizer to perform at peak efficiency. We recommend OxySpa non-chlorine MPS shock, although dichlor granular chlorine is also a good shock to use at startup and to correct occasional water problems if they occur. (Dichlor should be pre-dissolved by itself in a plastic bucket of water, prior to adding to the spa water).

Note: If using Bromine Tablets as your sanitizer, the MPS compound in OxySpa also activates the bromide ion (which by itself has no disinfecting capability) to become bromine, which then rapidly becomes the active sanitizer: hypobromous acid, in spa water. Upon reaction with bacteria and other contaminants, hypobromous acid is reduced back to bromide ion, ready to be reactivated again by the next dosage of Oxy Spa shock.

Balance your alkalinity and pH

Control your water balance.

When the mineral components of spa water are correct proportion to one another, the result is balanced water. Balanced means that it is neither too alkaline (high pH) which causes destructive scale buildup on equipment, nor too acidic (low pH) which may erode plumbing and cause costly damage to spa pumps, seals and heaters. Balanced water has a more pleasant feel to the skin, and allows your sanitizer to work more effectively. We take periodic measurements of spa water with test strips to achieve balance.

Total Alkalinity (TA) & pH

TA is important. It is the measure of all the alkaline material in the water and really an indicator of the ability of the water to resist changes in pH-- the water's buffering capacity. Too high TA is much less of a problem than too low. Always adjust TA first, then check your pH. Maintaining the proper TA will often bring the pH into line automatically. Water chemistry is balanced by adjusting its TA and pH with compounds such as Alkalinity Increaser, pH Decrease and pH Increase.


The hardness level of spa water-- measured as the amount of dissolved calcium,  is also important. Insufficient calcium hardness can sometimes promote equipment corrosion and also result in water foaming problems. Although there is no practical way to reduce extremely high hardness levels, it is easy to increase levels which are too low by adding Increase Calcium. NOTE: Increasing calcium hardness is not recommended or necessary if using Cleanwater Blue bactericide-algicide.

Stain & Scale Prevention

To prevent problems with spa shell staining and scale formation, when refilling your spa, be sure to add mineral stain & scale preventer. If using Cleanwater Blue, the only compatible stain & scale inhibitor is Cleanwater Purge.

Go to Preparation & Maintenance for complete directions.

PreFresh Filling Filter

Start out with Better Water

The PreFresh Filling Filter reduces impurities including: scale, iron, lead, mercury and other heavy metals, plus chloramines, hydrogen sulfide, even odor-causing organics and pesticide residues. Beginning with pure water reduces demand on your sanitizer while making water balance easier. A must for well water users or where local source water is less than ideal.

spa customers write Consumer Reviews
OxySpaNon-Chlorine Shock
"It's about a 15 mile drive from our home to the nearest spa store, so I thought I would give The Spa Depot a shot since you have free delivery. Wow!! Your Oxy Spa is half the price I was paying here for non-chlorine shock. Works excellent and I want you to know we will be back for our other supplies when we run low."

Ron & Julie Peterson
New Haven, CT

Spa Depot, The, Spas & Hot Tubs - Dealers, Olympia, WA

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