Having “hard water” means you have a lot of calcium in your water, and “soft water” means you have less, as it comes out of the tap. Minerals like calcium and magnesium naturally occur and dissolve into water over time and can be present at different levels depending on where you live and where your water comes from. Both hard and soft water can negatively impact your hot tub water and components, so it’s important to understand how to keep your water chemistry balanced no matter what type of water you’re dealing with.  

Does Hard Water Affect a Hot Tub?

Hard water contains a high concentration of minerals, primarily calcium and magnesium. When hard water is used in a hot tub, it can lead to problems. If you live in an area with hard water, you’re likely already familiar with scaling. You’ll see it on your shower head, faucets, dishwasher, etc. As the water in your hot tub evaporates, the minerals can precipitate and form scale deposits on the hot tub’s surfaces, interior shell, plumbing, and heating elements. Scale buildup can reduce the efficiency of the hot tub’s heating system and circulation, leading to increased energy consumption and potential damage. Hard water can also clog the jets and filters of the hot tub, reducing their effectiveness. 

Calcium hardness and water hardness are the same thing. Minerals like calcium and magnesium exist in all water sources, and this presence of minerals is what makes water “hard.” Even though it’s not a caustic chemical like chlorine or muriatic acid, calcium can cause significant damage to your hot tub if it’s not managed properly. Depending on where you live, your water may be softer or harder. If you’re not sure how hard the water in your home is, you can get a kit to test it. Most spas and hot tubs will be fine with calcium hardness levels of up to 400 parts per million (ppm), otherwise you may begin to see signs of scaling and cloudy water conditions.

The best time to test your hot tub for calcium hardness is immediately after it’s filled and while the water is still cold. Most treatment products for increasing calcium levels work more efficiently in cool water than they do in hot, so we recommend you test the calcium levels every time you freshly fill your tub. High calcium levels (common in water abstracted from ground sources) can lead to scaling and scale deposits forming, as well as cloudy water. Low calcium levels can cause foamy water and corrosion of metal surfaces within your hot tub. Calcium levels should be maintained at an ideal level of between 200 mg/l – 400 mg/l (or parts per million).

How to Deal With Hard Water in a Hot Tub

Dealing with hard or soft water in a hot tub requires some specific steps to prevent and address the issues associated with high or low mineral content. Start by testing the hardness of your hot tub water using a water testing kit.The amount of both calcium and magnesium dissolved in the water is called total hardness. Some kits only measure total hardness, and not calcium hardness alone which isn’t a big deal, it’s enough to go by the total hardness to adjust calcium levels. The measurement is typically expressed in parts per million (ppm) or grains per gallon (GPG). A water hardness level above 150 ppm or 8.5 GPG is considered hard water.

Before filling your tub, consider using a pre-filter or a water softener system to reduce the hardness of the water. These devices remove minerals from the water before it enters the hot tub, helping to prevent scale buildup and other issues. Some hot tub owners use scale inhibitors to prevent the precipitation of minerals and the formation of scale. If you notice scale buildup on the hot tub’s surfaces, you can use a descaling product or a mixture of vinegar and water to dissolve and remove the scale. Be sure to follow the manufacturer’s instructions for descaling your specific hot tub model.  If you live in a soft water area and need to increase your calcium levels, you’ll need a hardness increaser.

Regular testing and adjustments are key to managing both hard or soft water effectively and keeping your hot tub in good condition. When balancing the calcium levels, we would suggest waiting two to three days before retesting, as these products can take a while to fully dilute. Proper water chemistry and keeping up with routine maintenance can help prevent scale buildup, maintain water clarity and keep your tub running safely and smoothly.

Remember that maintaining proper water chemistry is essential not only for preventing scale but also for ensuring the safety and comfort of hot tub users. If you’re unsure about any aspect of hot tub maintenance, give us a call at 970-879-4390 or contact us here.