What we had were two separate water systems.
One was directly from the well which feeds the house (and fills up the 5000 gallon water tank). The other is the 5000 gallon water tank that has a booster pump on that system. The water tank system feeds the lawn sprinklers and tree water around the house, but the well fed the house and Loretta's garden. I wanted to have her garden also connected to the water tank system so the house would always have good pressure, even if the sprinklers or garden watering was going on at the same time.
What I did was connect the well system to the water tank system by adding a couple large valves.
Now, by turning a couple valves, we can:
a) water the garden with either the water tank system or the well system.
b) use water to the house via either the water tank or well, in case one of the pumps ever failed.
c) we can even turn the valves so BOTH systems feed the house and garden(s) together if we wanted.
d) continually purge the 5000 gallon water tank with fresh water daily so if we have to live off it, it will be good water.
Here is a photo of those valves and the two system pipes connected.