Being that I have some Italian in me and I talk with my hands, seeing it in person would be better for me to explain it.
Also, I have not done a WC yet, so the process is still new to me. But I think it goes something like this:
I have a dedicated Iwaki 40 RLT pump for WC. It is connected to the sump and when I want a water change, i would turn off the main return pump and then turn on the Iwaki 40 pump. it will empty the tank water to the drain system that is under the crawl space ( I believe I have a pic of that on my blog site). Once I have removed 35-40 gallons of water from the tank, I will turn off the Iwaki 40 and then turn on a value that is connected to the mixing vats..it will automatically fill the sump, once the sump is filled, i will turn on the main return pump..WC is done..
I was thinking about oscillating them on/off with timers, but then Jan made a point about possibly wearing out the pumps by doing this, so I am considering to have them both go 24x7. the way the are laid out I will get a full circle motion in the tank.
As far as the barrel, I used 3 gallons of white vinegar each barrel and filled them with water. It still needs to be rinsed some more, but I am going to wait until Jason cuts a hole on the top of them, so I can get my arms in their to work. BTW, did you know that one of the barrels has a hole in it?? I filled one to the rim, and the rim has a small hole which leaked on the garage..no biggie, but I know now not to fill them to the rim.
If you are free this weekend, you are welcome to stop by.