From a clogged or defective circulation pump, or dirty spa filter. For Model: Compatible with 09/2020+ 680 Series, 03/2020+ 780 Series, 04/2017+ 780, 10/2016+ 980 Claremont/, 2016+ 880 Series. For Sweetwater & Spas Models: Compatible with All 2003-2004 Sweetwater Models, and 2015+ J-500 Series, 09/2015+ J-400 Series, 2016+ J-300 Convertible Models, 02/2020+ J-300 Models, 10/2020+ J-200/J-100 Models, 2002-2003 J-320, J-330, and J-340 Models, 2004+ J-335, J-345, 2007+ J-355, J-365, J-375 Models, 2007+ J-230, J-270, and J-280 Models with the Circulation Pump Option, 2002-2015, J-300 LED Series (With Curled Finger Connectors), 2011+ JLX, models.