valerie_cct
Hi, it's not that you will get plugged up with tap water, just that sometimes much of the water will be absorbed into the body from the colon. This can cause uncomfortable bloating and dilution of normal body electrolytes such as Sodium and Potassium.
If you are otherwise in good health and using a standard enema bag full of water there are seldom any serious consequences other than the bloating. Sometimes you will experience a release an hour or more afterwards that will provide welcome relief.
The reason this happens is that the body contains higher concentrations of electrolyte solutions than does the plain water in the colon, and by a process of osmosis water will pass through the wall of the colon into the body. Look up osmosis on Wikipedia.
Essentially, water will cross a membrane (like the colon lining) in an attempt to equalize the concentrations. This is the opposite of the way a Fleet disposable enema works. The Fleet contains a highly concentrated solution of Sodium Phospate that draws water out of the body into the colon to provide the water to stimulate a movement.
Hope that helps, Valerie