Rainwater Storage Gauge

Not only on ecologically grounds but also economically it makes sense to collect rainwater for use in the garden and increasingly for `grey water` domestic use. People who take rainwater collection seriously use large underground tanks for storage. The problem now arises, how can the water level be determined without lifting the tank hatch and peering in? One solution is to use float switches mounted at different heights in the water tank, and to use a row of LEDs mounted remotely to show the water level in the tank.