Take the guess work out of knowing if your waste tank is full with our over-flow-indicator. This water tank overflow indicator lets you know when the waste-water tank is full and needs to be emptied. When the red tip is low, that shows the tank has plenty of space left. When the red tip is at the top – that shows it is full. Simply peek under the cabinet of your portable sink and easily tell whether it’s time to empty and refill tanks – or not! Call us today to order 1-800-513-8562.