We have a natural gas hookup to our standard water heater in the basement.

There's an issue with the gas right know where there actually is none at the moment.

Anyway, is it safe and possible to connect a portable propane tank (from the gas station) to the water heater?

The natural gas line connections would allow me to thread a connector onto it, after removing the pipe cap at the bottom of the pipe. At the top of the pipe, there's a shutoff valve that can be turned off to prevent the propane from going back up into the other gas lines... the only place it would then flow is into the regulator and out into the burner.

Is it as easy as shutting off the switch at the top of the pipe, connecting the propane tank in place of the endcap, flow the propane and light the pilot?

How long should a standard propane tank from a gas station last before it needs to be switche d out?