We may be using different methods of filling the water trough. With the motor running, I gradually add water in the trough until I can see it running over the top of the grinding wheel. This is the same way I fill the trough using the Original grinding wheels. The difference is that the original wheels absorb some water, and I have to add some gradually until the stone no longer absorbs water. Diamond and CBN wheels do not absorb, therefore, once the water starts to flow over the wheel, that is enough. I do not pay any attention to fill lines in the trough; the water flowing over the wheel is the indicator.
I have found that this method uses less water and dramatically reduces the amount of spilled water. The other technique which reduces spill is using the turkey baster. I usually have a very small amount of spill, perhaps ten to twenty drops. I use the Tormek Rubber Mat. It is luxurious, although not inexpensive. I like Rick's lipped tray idea, and could happily work with it. With such a tray, I would probably not bother with the rotating base.
Using this fill method, I need 125ml with the T8; 200ml with the T7; and 75ml with the T4. The lesser amount with the T8 is due to the rounded bottom design of the trough which more closely hugs the wheel and the lift, which raises the trough closer to the wheel. These quantities are only for grinding with the edge of the wheel. I do not yet use the side of the wheel. This may change if I decide to change to flat grinding turning skew chisels and possibly other operations. For most operations, I see no need for flat grinding.
Using Sharpco's cost figures ($49.95 for 300 ml), I arrive at $.1665 per ml. Let's be sloppy in our math, and round that to $.17. That works out to $.85 for 3ml (125 ml water) or $1.36 for 8ml (200ml water). Divide that cost into the revenue generated by the knives sharpened. For easy math, let's choose a very slow day and only $100 income. That makes the cost of the ACC used around 1% of the revenue. Reusing it would lower that cost.
In the future, I will certainly stock up on ACC at woodworking shows with the typical unadvertised 20% discount.
Ken