I've seen where the tank top is a handwashing station. There is a faucet on top and a small basin in the tank top, when you flush, the inlet is connected to the

I've seen where the tank top is a handwashing station. There is a faucet on top and a small basin in the tank top, when you flush, the inlet is connected to the faucet. You wash and the soap water goes into the tank for use on the next flush.