Can You Put Pool Chemicals In A Hot Tub?

By Jon Filson

Hydropool Hot Tubs and Swim Spas

Can You Put Pool Chemicals in a Hot Tub?


If you own both a hot tub and a swimming pool, you’ll surely also own a hefty stack of chemical additives.  If you’ve casually looked at these chemicals, you might think there’s no difference between hot tub chemicals and swimming pool chemicals.  However, if you look closer, you’ll notice that the swimming pool chemicals come in much higher concentrations than those made for the hot tub.  For this reason, if you’re asking the question, “Can you put pool chemicals in a hot tub?” you’ll understand why the answer is an emphatic, “No.” To expand on this subject, we’ve come up with a list of differences between swimming pools and hot tubs that underline this point.


Water Volume


It’s quite obvious that a swimming pool holds much more water than a hot tub.  And it’s for this reason that swimming pool chemicals are manufactured to have much higher chemical concentrations than those made for hot tubs.  These higher concentrations allow swimming pool owners to avoid carrying and storing massive quantities of chemicals.  But these same highly concentrated chemicals can cause wild fluctuations in the pH levels, total alkalinity measurements and chlorine levels in the small volume of water found in a hot tub.


Water Temperature


Hot tub water can run a good 15 degrees Celsius higher than that found in a swimming pool.  The higher water temperatures found in a hot tub accelerate chemical reactions and cause more of them to occur compared to those taking place at the lower temperatures found in a swimming pool.  Because swimming pool chemicals are already manufactured in higher concentrations, their use in a hot tub can cause rapid and uncontrollable fluctuations in the various levels that need to be kept in balance.


Water Circulation


The fact that hot tubs have a higher concentration of water jets per square foot than a swimming pool means water is circulated much faster in hot tubs.  This faster mixing of the water causes chemical reactions to occur more quickly.  Combined with highly concentrated swimming pool chemicals, this will also cause uncontrollable fluctuations in the water balance levels.




The high temperatures and churning waters of a hot tub will inevitably lead to water evaporation.  This evaporation, in turn, causes the levels of chemicals in the water to become more concentrated.  Hot tub chemicals are manufactured to take this level of evaporation into account.  Swimming pool chemicals, which are more concentrated, to begin with, can become super concentrated if used in a hot tub.  This can result in skin irritation and/or equipment damage.


Water Usage


Because of their greater capacity and the way that swimming pools are used, there is typically much more activity found in a swimming pool than a hot tub.  The reduced water usage in a hot tub makes it more vulnerable to dramatic changes in pH, total alkalinity and chlorine levels.  If swimming pool chemicals are used in a hot tub, these changes can be especially unmanageable.


Chlorine Tablets


Chlorine tablets made for a swimming pool are too acidic to be used in a hot tub.  They can reduce the water’s buffering capacity which can cause a severe drop in pH.  Rebalancing the water to allow bathing could possibly take days.


Soda Ash


Swimming pool soda ash, used to raise pH levels, is much too concentrated to use in a hot tub.  The combination of a small volume of water and high temperatures can cause pH levels to skyrocket to such a point that the only way to rectify the situation is to empty the tub and refill it with fresh water.


To learn more about caring for your hot tub, download a hot tub buyer’s guide.

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