I have an arts degree and am not an engineer, but I work in technical communications and have an aptitude for problem solving, so I'll give it a go.
Marek makes a good point about the acceptable leak rate. I've seen comments from others posted elsewhere that suggest that the seals have to cause friction, or the crew must be in suits to transfer between sections if the seals are loose. That is not necessarily the case.
In the SF tales I'm developing, I accept the limitations of labyrinth seals for preventing leaks of atmosphere and most ships/stations do not normally have the volumes adjacent to the transfer areas pressurized at all. With the air held behind bulkheads and the robust seals of standard hatches, there is no air to leak out through the seals that protect the juncture of the ship sections.
Here are some options for getting crew through the juncture without them getting into suits.
Use a pressurized tube with appropriate hatches at the ends that can couple to and detach from the rotating and non-rotating portions of the ship. Crew open one end, enter and close that hatch behind them. The tube detaches and its rotation is changed to match that of the other section, to which it is then connected. The crew open that hatch and exit the transfer tube. No pressure suits or major hassle. Power/data is transferred through slip rings elsewhere, or through cables in the transfer tube wall and slip rings.
Instead of just a tube that changes spin, a pod could be transferred through an unpressurized junction and spun to connect with the ship sections as needed, sealing to hatches directly or moving in and out of volumes that can be evacuated and pressurized.
A non-rotating tube extends into the rotating section. The adjacent chamber -- perhaps the size of a small room -- is unpressurized when not in use for transferring crew. When that chamber is in use, it is sealed and air is pumped in. Some will leak out, but at a slow rate, and only from that limited volume. When not in use, the transfer tube volume is pumped out to conserve the atmosphere. Again, no air there means no air to leak out through the seals. Some is lost, but at a much slower rate than if it was pressurized at all times. The small cumulative loss of air from the transfer section is balanced with air from the much larger volumes in the rest of the station/vessel. If you really need to pipe water into and out of the rotating section, a pipe or hose could run through an axial transfer tube, down the center in the case of a larger tube or in the wall of the tube so long as it connected to the rotating section at the actual axis with enough room that crew transfer isn't hampered.
The tube is optional. Instead, have the two sections meet with two hatches that can be sealed, perhaps a meter apart, or even less. The smaller the volume the faster it can be pumped full or evacuated.
In options 3 and 4, the crew start by pumping air from tanks into the transfer tube section, then open the hatches one at a time or simultaneously, move through into the other section, then close the hatches. If they need to go back and forth, they keep it pressurized, but perhaps closed. If not, they pump the air back into tanks, minus what little amount leaked out in the short time it was in use. Just don't have a phobia about not being able to breathe...
Leakage is not a problem if there is nothing there to leak out.