I did an internet search to find info on installing yard hydrants. Dean asked a question in Sept. '07 which was very similar and the answers he received were helpful, but I am still confused.
One of the answers said that a hydrant or spigot can be connected in the main water line between the pump check valve and the pressure tank. I want to make sure that is correct. It seems to me that any outlet installed before the tank would cause the pump to run constantly to supply the open faucet. Is that true or am I all wet with that thinking?
Does the water at the faucet actually come back in the line from the pressure tank?

Yes, the water from the tank will return to the hydrant by the tank supply line. The pump will come on when the pressure in the tank (which includes the supply line) reaches the preset low pressure. If the pump comes on while the hydrant is open, the water will flow to the tank and/or the hydrant depending on which has the least pressure. If the pump can supply more water than the hydrant is letting out, the tank will refill while water is flowing out the hydrant. If the pump cannot provide more water than the hydrant is capable of letting out all of the water will flow to the hydrant. However, this is no different than all of the water flowing into the tank and immediately flowing out to the hydrant.

Thanks Harold! That pretty well answered my question. I'm still wondering if that hydrant being opened for extended periods (it will be used for watering a garden) will cause problems with pump wear. I guess it depends on how much water gets past the hydrant to fill the pressure tank back up and switch off the pump?