Two things: your health and your equipment.

• Germs. Warm water breaks down sanitizer quickly. In a poorly maintained tub, a germ called Pseudomonas can cause “hot tub rash,” an itchy, bumpy rash that often shows up a few days later. Legionella bacteria can grow in hot tub water and, when breathed in as mist, cause Legionnaires’ disease, a serious type of pneumonia, or a milder illness called Pontiac fever.
• Equipment. Water with low pH or too little calcium is corrosive to metal parts like the heater. High pH or too much calcium leaves scale on the heater, plumbing and shell, which can shorten equipment life.

The CDC recommends keeping free chlorine at least 3 ppm (or bromine 4–8 ppm) and pH between 7.0 and 7.8.

Source: CDC, Preventing Hot Tub Rash; CDC, Protecting Yourself from Legionella in Hot Tubs; Coast Spas owner’s manual; Arctic Spas owner’s manual

Neither. What matters is the right amount and a balanced pH. Too little sanitizer lets germs grow. Too much chlorine, or pH that’s out of range, can irritate skin and eyes.

That strong “chlorine smell” usually isn’t too much chlorine. It’s chloramines, which form when chlorine reacts with sweat, lotion and skin oils, and they’re a sign the water needs attention. A properly treated tub has little odor. Showering before you soak helps too.

Source: CDC, Stay Healthy in Hot Tubs; CDC, Preventing Eye Irritation from Pool Chemicals; Poison Control

It varies widely with tub size, sanitizer type, how often you soak and how carefully the water is kept. We haven’t found a reliable published average, so we won’t quote one. Many owners under-treat, and others over-buy and let products expire. Ovastra’s model is designed to estimate your tub’s actual usage, so you buy what you need.

Public hot tubs are expected to test sanitizer and pH at least twice a day. At home, test regularly and more often after heavy use. Your Ovastra schedule tells you when to test and which packet to add.

Source: CDC, Protecting Yourself from Legionella in Hot Tubs

Pre-measured, single-dose packets in four color-coded chemicals: Sanitizer (slate), Shock (orange), Balance (green) and Hardness (gray). The mix and quantity are based on your tub’s estimate.

You answer a few simple questions: tub size, sanitizer type, how often you soak, and so on. Our adaptive model uses those to estimate how much of each chemical you’ll use. As you log test results or your habits change with the seasons, the estimate adjusts.

Not in the usual sense. Instead of a fixed box at a fixed price, Ovastra estimates what your tub will use and charges the card on file for that. Pricing will be announced at launch.

Ovastra is coming soon. Shipping details and areas will be announced at launch. Packets are flat and light, so they fit in a mailbox-sized package.

Yes. You can pause, change or cancel anytime, with no long-term contract.

Use them as the label directs. Keep packets sealed, dry, and out of reach of children and pets. Never mix chemicals together; add each packet to the water separately. Single-dose packets mean no scooping and less handling.

Source: Poison Control

The CDC advises keeping water no hotter than 104°F (40°C), not letting children under 5 use hot tubs, avoiding alcohol before or during use, and showering before you get in. If you’re pregnant, talk to your healthcare provider first.

Source: CDC, Stay Healthy in Hot Tubs