Can You Put Pool Chemicals in a Hot Tub?

Can You Put Pool Chemicals in a Hot Tub?

If you own both a swimming pool and a hot tub you may have experienced the following scenario.  You’ve run out of chemicals for your hot tub and aren’t looking forward to making a run to go out and buy some more.  In fact, you have an abundance of swimming pool chemicals that appear to be the same thing.  Can you put pool chemicals in a hot tub and save yourself from having to drive into town to get the chemicals specifically designed for the hot tub? 

Unfortunately, the answer is “No.”  You’re going to have to make the trip if you want your hot tub to continue to function properly and provide a safe bathing environment.  Your hot tub isn’t just a smaller version of your swimming pool that can use the same chemicals interchangeably.  Putting pool chemicals in a hot tub can alter the pH levels to the point of actually causing damage.  In this article we’ll go over the differences between hot tubs and swimming pools that make using the same chemicals for both a very bad idea.

Volume

It’s not difficult to realize that a hot tub holds much less water than a swimming pool.  Because of this, swimming pools require chemicals that are much more concentrated than those designed for use in a hot tub.  The smaller volume of water found in hot tubs means the chemicals needed to keep the water clean and fresh are much more diluted than those used in a swimming pool.

Temperature

Hot tubs run at a much higher temperature than swimming pools.  The water in most hot tubs reaches a temperature of about 40 degrees Celsius whereas your average swimming pool water runs at around 25 or 26 degrees Celsius.  This difference in water temperatures causes a difference in the chemical reactions that take place when applying the additives.  Using swimming pool chemicals in a hot tub can result in dramatic pH levels changes that can be difficult to rebalance.

Circulation

Hot tubs have many more water circulating jets per square foot than a swimming pool.  This results in the water (and also the chemicals) in a hot tub being circulated much faster than the water in a swimming pool.  This is part of the reason that swimming pool chemicals are much more concentrated than hot tub chemicals.  Using highly concentrated swimming pool chemicals in your hot tub will quickly put the water out of balance.

Evaporation

A combination of the high-water temperature and force of the water jets causes hot tub water to evaporate much faster than that of a swimming pool.  This rapid pace of evaporation means the chemicals in a hot tub quickly become concentrated.  For this reason, swimming pool chemical are far too potent for use in a hot tub.

Capacity

Because hot tubs hold fewer people and typically experiences less rotation in and out of the water by the bathers, hot tub water is more prone to erratic pH level changes.  By using chemicals that are designed for pool use, pH levels in a hot tub’s water can quickly spiral out of control. 

Chlorine Tablets

The acidity of pool chlorine tablets has a nominal effect on a large body of water, but they can quickly knock a hot tub’s total alkalinity buffering capacity out of whack.  Controlling the pH levels become near impossible after using the tablets in such a small volume of water.

Soda Ash

Soda ash, used to raise the pH levels in a swimming pool, can cause a massive pH increase in a hot tub to the point that the water is no longer safe to bathe in.  Restoring the balance will typically require emptying the tub completely and starting afresh.

Download a hot tub buyer’s guide to learn more about maintenance and self-cleaning models.

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