BigK, I'll give you that.. if you don't know the water, don't use the water.
Single story motels, at least all the ones I've ever stayed at, don't have roof-top tanks - they're closed water systems on either a well or on city water. Municipal water supplies are pretty tightly regulated here in the USA, and even private wells are now. (I know, as I recently needed to fix the pump in my well, and while looking for well contractors found out that what used to be a pretty casual industry is now VERY tightly regulated). High-rise hotels, I couldn't tell you though.
The risk of becoming infected from an enema at home is extremely low, unless your water comes from a shallow well and you weren't too careful about where you put your septic system.
Norovirus - previously known as Norwalk Virus, but we didn't want the fine folks in Connecticut to feel bad - is just one of many possible things BAD water can transmit, but you can get this just as bad from drinking it as from taking an enema with it.
So I think we agree.. although I think you missed the most important part of my post:
".. if the water is safe to drink, it's safe to give from the other end. Now, if your tap water ISN'T safe to drink, it's also not safe for your bottom end.. but in that case what to use in your enema is the LEAST of your worries." as in DRINKING the water isn't safe. Norovirus infected water isn't safe for either end.. why would you drink it?
Sounds to me the water you're talking about in hotels and cruise ships isn't so safe to drink.. and I will REALLY think twice about drinking the water when I stay in a large hotel.. never mind taking an enema with it! In that case, bottled water for EITHER end, no?
On a cruise ship, by the way, the water is desalinated. While technically that's "filtered", the pore size is such that even the salt can't migrate.. bacteria and viruses from the sea really aren't the issue. It's what's introduced in the REST of the system that's the issue.