When I take a single 2 quart water with 2 teaspoon castile soap enema I usually do not take a salt water enema but when I take a series of say 3 or 4 soapsuds enemas then I follow with a retention coffee enema followed by a saltwater enema.
I avoid a plain water enema because I do not find them good for cleansing or flushing out soap. I retain them too long and absorb too much water. I prefer to take a salt water /baking soda enema (2 teaspoons of each, salt and baking soda, per quart of water).
This is my personal preference.