You're supposed to do water with Sea Salt when doing cleansing/flushing enemas, that takes care of the electrolyte problem and hard water problem. The colon is where we absorbe a lot of our minerals and electrolytes, so enemas are actually more balancing to PH/minerals than not! :)
As long as you do them on an empty stomach, avoid them when suffering from diarrhea, occasionally supplement with probiotics, use good Sea Salt in the water, enemas are perfectly fine. :)