Like apparently a number of people my shower drain is a bit above the floor of the shower and so it leaves 1/8 to 1/4 of an inch of water when I am done. It also like collects dirt.
I have see several threads on this problem in several FGRVs. About half being scamps like mine. And none of the fixes seems doable and very expensive. It looks mine would involve completely replaceing the shower floor. Not reasonable. So I thought I would have to live with it. Until I realized I was defining the problem in terms of the solution and not the problem.
The problem is that the water doesn't all drain, not that the drain is a bit higher thant he floor. Thaat problem causes the key problem. The problem is that I need to get rid of the water and I solved that a totally different way. The scamp
has an additional pump to take water from the shower drain and pump it up into the gray water tank. That means that there is a pump sucking water out of the drain. So there is suction at the drain. If I can suck the water into the drain then my problem is fixed.
All I had to do was harness the existing suction. What I did was got a rubber stopped that would fit the drain. And then I got some clear tubing, in this case 1/2 inch outer diameter. I cut off a short length of it. Then I drillled a 1/2 inch hole in the stopper. Put the stopped in the drain, start the pump and then use the end of the hose to pull all of the extra water off the floor. Works great.