First, the enema should be about 103F at preparation time.
Now, regarding tap water for enemas: tap water is fine for an occasional enema (once or twice a month), but if you are using enemas on a weekly or more frequent basis, this can cause an electrolyte imbalance, specifically, a sodium deficiency.
This is not good, despite the initial reaction some people have about sodium levels. The neurons in your brain depend on sodium regulation to open and close openings in the walls of brain cells that allow us to think as well as performing basic life essential functions, such as heart rate modulation, kidney functions, blood volume, and virtually every essential life function.
If you take enemas frequently, you should be using an isotonic (electrolyte balanced) solution, such as can be achieved by a teaspoon of table salt
per pint of water, or better yet, Sea Salt