The Manual shows you what hose to pinch off,
I bought a 3/4" plastic valve and 2 - 3/4" threaded hose barbed fittings at Lowe's and cut it into that hose. It has the same I.D. as the hose and I can shut it off if needed to tow. I leave it open normally and would only need to close it if I had to in case of an issue where I had to pull it.
I also added a small automatic bilge pump that is direct to the battery and discharges out the back under the tow hook. I put an in line fuse in an accessible area under the seat to disconnect it if needed. Also fused it at the battery.
I tie the ski at next to my boat on the weekends and gives me peace of mind if anything starts to leak. so far dry as a bone inside after 2 -3 days in the water.
I can try to get a picture of both if you need it.