@gwhap - You obviously have some knowledge of science, but apparently not much in nuclear physics. Heavy water IS slightly heavier than regular water because it holds one hydrogen which has a higher atomic mass that normal hydrogen. It requires special (and very expensive) equipment to isolate and separate the heavy molecules from the normal ones. As a rule, only governments have the money to do the job. They do it because heavy water is the thing that turns an atomic bomb into a hydrogen bomb! There are a few “peaceful” uses for the stuff, but it is priced WAY above the price range of the ordinary person. Believe me, if I had enough heavy water to do an enema, I wouldn't be pumping it up my ass!
Actually what you described is semi heavy water (HDO) where on one of the hydrogens is deuterium. Deuterium oxide (D2O), as the reference below notes, is the heavy water. In D2O, each hydrogen is actually a proton and neutron in the nucleus of the atom. Although a stable isotope, the properties of D2O are different enough that, at high concentrations, could cause issues with certain body processes over a long period of time. However, it is difficult to maintain this high level of D2O in the body given the abundance of normal single proton hydrogen in the universe. So, from the standpoint of an enema, it probably would cause much of a problem except to your wallet.
I worked several years at the Savannah River Site (SRS) in the areas where the heavy water was produced and processed (from the Savannah River) as well as the tritiated water coming from the K-Reactor on the site prior to K-reactor being permanently shutdown. Although there was some concern about exposure to heavy water, the safety issue for certain radiation workers like myself was the exposure to and ingestion of tritiated water. Tritium (2 neutrons and one proton) is radioactive with a half-life of about 12.3 years (it decays at an approximate rate of 7% per year). It is a beta radiator (it produces an electron during decay). When it decays, one of the neutrons converts to a proton and “kicks off" an electron and anti-neutrino leaving a helium3 nuclei (2 protons and a neutron atom) behind. From inside the body, this is not good. And what happens to that anti-neutrino? If it encounters matter (and neutrinos stream through us day and night but rarely encounter matter, passing through us and the planet as if we don't exist), it annihilates and produces a short-lived gamma ray burst.
I was routinely tested (urine bioassay) to make sure that I wasn't exposed or that my exposure was at an acceptable level. I had no desire to glow in the dark.
Oh, and I use tap water.