A universal saline solution of one teaspoon of salt per pint of pure water is an isotonic solution.
A pure salt solution (NaCl) is isotonic, meaning that is will not draw water out of the body into the colon, nor will water from the colon be absorbed into the body.
A Fleet enema is a hypertonic solution which causes water from the body to be absorbed into the colon to stimulate peristalsis and result in a bowel movement.
If you stick with regular table salt or Sea Salt at one teaspoon per pint, the water you use for your enemas will be neutral with no worry about upsetting the electrolyte balance of your system.