Is there secret bacteria building up in your hot tub water? If you haven't drained and cleaned your hot tub in the last 3 to four months, you've got bacteria and contaminants building up inside your hot tub pipes and it's completely resistant to your regular chemicals. That means as the water circulates through your pipes, that nasty buildup will cause cloudy water, scum lines, and slime. So every 3 to 4 months, use a hot tub plumbing cleaner to purge that hidden scum in your pipes. Follow us at Swim! University for more hot tub care tips throughout the year.