You need to find out exactly what is making the water hard. There are different types of hardness. Calcium, Sulfur, Lime...there are literally dozens of things that can send a PPM meter off the scale without telling you what it actually is.
It may turn out to be great water.
Most local governments provide free water testing. Check your local government to find out the procedures. Typically, you'll go pick up a specimen kit that gives you all the instructions on how to take a sample and return it to the testing facility. You'll normally get your results within a few days.
For all you know at this point, it could simply be lime rich...which is excellent for outdoor watering.