I'm not sure what you mean about the float valve and RO/DI. I have a float valve in a 30g covered barrel, when it is triggered by low water it triggers a valve that opens and begins pushing water through the RO/DI. TDS going in is around 210, coming out (into the barrel) is 0. I have a 15g container on the top of the cart used for mixing salt water. I usually do it the day before I need it and leave a powerhead running to keep it circulating. Here's a photo of the cart. I have an extra maxijet 1200 I use to pull water from my sump into the container in the bottom, then pump it from the container back out to the yard or toilet. I store my extra 5g RO water jug on the bottom as well.