You should NOT use softened water on your garden or houseplants. Here’s what an ag agent at Texas A&M about it. “Softened water is not recommended for watering plants, lawns and gardens due to its sodium content. Care must also be taken that water used in recharging a water softener be disposed through a storm drain or sewer due to its damaging effects. If you are on a septic tank, the logical method of brine disposal is to discharge the brine into the septic tank and soil absorption field where some leaching of sodium salts will occur. Other alternatives include a separate holding tank which could be evacuated by a vacuum truck or a separate disposal field or discharge point that does not affect neighbors’ property.” Get a bypass installed and use that hard water. The plants may benefit from the minerals in the water but will suffer from the sodium in the water softened water.