Your hot tub must stay at a Ph level of 7.2 to 7.8. If it's 7.2 or lower, your water is overly acidic, which might make your sanitiser less effective and cause eye burn and itching. High acidity can also cause extensive damage to the components of your hot tub. When buying a hot tub for your home, you must consider these Hot tub test strips a must-have accessory.
https://www.thehottubsuperstore.co.uk/water-testing/