For people who have been around swimming pools and hot tubs long enough, they may have noticed that although there are distinct categories of swimming pool chemicals and hot tub chemicals, the ingredients in these water additives are nearly the same. Does this mean these chemicals are interchangeable regardless of whether you’re adding them to a hot tub or swimming pool? Are hot tub and pool chemicals the same? To clear up any confusion between hot tub and swimming pool chemicals we’ve come up with an article explaining the differences and why you shouldn’t swap between the two.
Different Chemical Concentrations
Although swimming pool and hot tub chemicals may contain the same ingredients, the major difference between the two is the concentration of those active ingredients. Swimming pool chemicals are much more highly concentrated than hot tub chemicals. This is the major reason why you shouldn’t switch between the two. Using highly concentrated swimming pool chemicals in your hot tub can radically alter the water chemistry to the point of having to empty and refill your hot tub. Conversely, adding weakly concentrated hot tub chemicals to your swimming pool might not create any change in the water chemistry whatsoever. This difference in chemical concentration is only exacerbated by other differences swimming pools and hot tubs as we’ll see below.
Differences in Temperature
Chemical reactions occur much more quickly and more robustly when you increase the temperature in which they’re taking place. Chemical reactions are the result of colliding particles. And when the temperature is increased, the particles move faster and collide more frequently. This results in faster and more vigorous reactions. Of course, hot tub water can be as much as 15 degrees hotter than a swimming pool. And partly for this reason, hot tub chemicals have lower concentrations compared with swimming pool chemicals. If you add swimming pool chemicals into hot tub water, the chemical reactions may be so robust that your water chemistry becomes radically altered and impossible to properly control.
Differences in Water Volume
Another reason that swimming pool chemicals are so highly concentrated is due to the large volume of water they have to affect. Hot tubs, on the other hand, have relatively small volumes of water and don’t need high concentrations of chemicals to effectively change the water balance. By adding highly concentrated swimming pool chemicals into the small volume of hot tub water you’ll find your water chemistry quickly becomes uncontrollable. Similarly, if you add hot tub chemicals with low concentrations into a swimming pool, you’ll find they have barely any effect whatsoever.
Differences in Water Circulation
Water circulates in a hot tub much faster than it does in a swimming pool. This is a consequence of the smaller volume of water and the higher power of the water jets. The rate of water circulation also affects the rate of chemical reactions. The quicker the water circulates, the quicker the chemical reactions will take place. If you add to that the relatively high concentration of swimming pool chemicals into a hot tub, you’ll have chemical reactions taking place much faster and more robust than they really should be. Not a good thing when you’re trying to achieve a fine balance.
Differences in Water Evaporation
Even though swimming pools have a much larger surface area than hot tubs, water typically evaporates from hot tubs much faster. This is a result of the higher water temperature and faster rate of water circulation. As water evaporates, the remaining chemicals become more concentrated. This can be problematic if you try to add already highly concentrated swimming pool chemicals to the hot tub water. You can expect the water chemistry to swing widely and erratically.
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