Our water here is very, very hard (city water, very hard). We have a water softener for the house, but the exterior taps used to fill the inflatable 200GAL tub are unsoftened (so the grass doesn't die, etc). Can I add some of the large pieces of softer salt from the softerner into the pool? How do I measure the amount I should put in? Any thoughts, or is this as ghetto as an idea as it reads as I type it out...