count how maney times you use the washing machine to fill the tank the same with the shower.in the shower if it backs up its full.open the valve up in a couple of days mine is leaking some i have a couple sewer tanks to fill also none of my gauges work ive had this big horn for 5 years now once a week i drain the tanks. all is good my washing machine fills my shower tank so i can leave it open all the time. good luck