Forget what the user manuals says, I know it states water based fluid is compatible and technically it is, however using water based fluid in either of these machines is not recommended. Using water based haze fluid in these machines will dramatically reduce performance and output by up to 50%. That being said you can go back and forth between oil and water if you choose but not very easily. Each change of fluid types requires deep cleaning of the system by following the steps below;
1. First, drain the haze liquid inside the tank.
2. Add a small amount (about 50~100c.c.) of pure alcohol (not the kind in your bar!) into the tank, and run the hazer for 3~5 minutes or until all the alcohol has filtered through the system.
After running the hazer please drain the tank again and make sure there is no alcohol residue left inside the tank.
3. Open the upper and side cover of the hazer and use a clean cloth, dipped in alcohol as well, and wipe down and clean the fluid filter connected to the tank outlet.
4 Also, Remove the filter inside the air compressor, open it up and wash out the filter gauze with alcohol and let dry.See attached picture
5. Reassemble in reverse order when all components have dried.
By the cleaning steps involved you can see why most people choose to stick with one type of fluid.
Hazers are really designed for larger shows in arenas and outdoor venues. If you want to look at a good water based hazer look at the HZ-400: http://www.elationlighting.com...Id=1&Category=Antari
But, my best suggestion would be to retire the HZ-100 and HZ-300 and move to a machine designed for water base fluid like the X-310: http://www.elationlighting.com...Id=1&Category=Antari
or even better the new F-3 Fazer: http://www.elationlighting.com...Id=1&Category=Antari
The F-3 uses the latest fog machine technology and works almost exactly like a haze machine with two exceptions; 1) It has a 3 minute warm up time and 2) It strictly uses water based fog fluid.
Hope this helps.