GreenStory Global's CYA remover is the easiest way to end chlorine lock without needing to drain your pool. Simply drop the pouch into your pool skimmer and let it do all the work. The CYA remover pouch works by adsorbing the CYA out of the water as it filters through the pouch. It works at any temperature and will reduce the CYA by around 10ppm per week without any other impact on pool chemistry. GreenStory Global CYA remover is made in the USA. Use 1 lb. bags for general maintenance and small pools up to 10,000 gallons, and 1.5 lb. bags for very high levels of CYA or larger pools.