Anny, have you tried putting the waterer up on a tall block atop a plywood platform as mentioned in another thread, and in a CORNER (they cannot knock it over in the corner, unless they try to perch atop it, which you can easily prevent with simple measures).
With four chickens I'd suggest that's your best option (with a 1 gallon waterer).
For completeness though I will show you my compact very small homemade waterer I was using in my tractor last summer, not as the main waterer (that was outdoors) but just so my 2 ISA Browns did not get too thirsty if I let them out a bit late:
This is really too small for 4 chickens though (in principle it could be sized up, but I can't think offhand of what materials you'd use so scrounging just the right things could be a real problem). Seriously, I cannot see why a properly-raised non-roost-on-able 1 gal waterer in the corner should not be quite satisfactory.
(Oh wait... stray brain cell firing... is yours the coop in the garage that we were discussing how to add an extra bit of roost to b/c you got an extra chicken? IIRC, the waterer and feeder are hung right in front of the popdoor? There's your problem, I betcha -- try reversing things, put the roost over on the popdoor half of the coop and the feed and water in the right-hand half (waterer in the corner). Honest, I betcha your problem is just having hanging feeders/waterers in a major traffic route
)
Good luck,
Pat