Check the listing for details. Sirona Spa Care Simply Waterline Control - 2 Pack. Condition: New. Listed at 49.98 USD. Sirona Spa Care Simply Waterline Control offers an efficient liquid formula aimed at averting waterline deposit formation in spas and hot tubs. Incorporate this product during spa start-up and weekly as an essential component of the Sirona Spa Care Simply 3-Step System. Product Features: Simply Waterline Control is compatible with biguanide sanitizers Patented formula controls and prevents waterline deposits on your spa shell for clean, relaxing results Use with Simply Oxidizer and Simply Sanitizer to create healthy, healing spa water Add to spa water at start-up and keep adding weekly for waterline deposit prevention Sirona Simply. The bromine-free, chlorine-free biguanide solution. Start Up Dosage: Add 1.5 fluid ounces for every 150 gallons of water. Maintenance Dosage: Add 3/4 fluid ounce for every 150 gallons of water.