Total Dissolved Solids (TDS) are the measure of everything that has dissolved in the water over time from numerous chemical dosages. High TDS contributes to cloudy water, makes balancing chemicals more difficult and can lead to increased chlorine usage. Test the TDS to find out if it is time to drain and refill a hot tub.Get test results in seconds with just one dip! Dip an AquaChek TDS strip in your pool or spa water for one second and remove it immediately. For a clean and healthy pool, test the water at each end a minimum of twice a week!Features:Measure totally dissolved solidsAquaChek TDS is the only test strip on the market that measures Total Dissolved Solids in pools and spas!One easy dip gives you accurate results in seconds.Checking TDS frequently helps you prevent hazy water, scale buildup and corrosion caused by high levels of TDS. Product information Product Dimensions 3.5 x 1.5 x 1.5 inches Item Weight 0.634 ounces Manufacturer AquaChek ASIN B00JH42VRA Item model number 561683