If you have control of your own database (which may be a bit of an assumption in some cases) then the addition of a single field (especially a simple logical yes/no flag) should be straightforward. But ... will that be enough?
If sensible use is to be made of the data, then surely more statements shall be required. For instance (and off the top of my head):-
1) Uses water internally (eg:- neonatal incubators, humidifiers).
2) Connected to cold water supply.
3) ditto hot water.
4) ditto treated water.
5) Drain considerations.
Surely it is better to look at the water issue from the "other end": asking the question "do your PM procedures take into account tasks such as":-
1) Cleanliness of water containers (cleaning out humidifiers etc.)
2) Cleaning filters.
3) Regular checks of water quality ... surely an "Estates" task?
Also, don't forget the various items in the clinical labs: water baths, and stills, come to mind.
PS: does your database make similar provision for PMG ... O2, MA4, Vac etc.? What about Steam, LPG and what-have-you? Again, what about "Estates" (or, if you like, "Facilities Engineering")? Or have "demarcation wars" now become a thing of the past?