We have had good luck with a coyote switch which shuts off the pump when the water level in the well drops below a critical level, then re-starts the well pump when the water rises again. We are in an area with very limited well capacities (about 1 gpm) and this enables us to store sufficient water for 4 families (in 2 large plastic tanks). In addition to the farm supply, why not call the septic tank folks in your area and ask for leads on plastic water tanks. Please feel free to e-mail me with any questions.George: I would like to use a water platic storage tank to supplement my well water in dry seasons. Where can I obtain a tank? Is there a valve or switching mechanism that determines when well water is running low and cuts over to tank water? If anyone else uses or has tried a similar system, was it successful? Many thanks in advance for any assistance you might offer.