Thanks to Tau on Discord (eww) for the answer!
Turns out you can split fluids using a multiple pipe and single pipes, if you make sure it’s completely full before you begin using it. The other key is to have multiple single pipes from the multiple pipe to the valve.
The valve only outputs when the pipe is full. Having two single pipes means when the pipe with the valve is emptied into the drum, the other single pipe fills it partway to help keep the fluid locked. Initially I had only one single pipe with a valve, and when the valve emptied the pipe I had the first fluid fill both sides.
When building this, just use some drums with fluid to fill the pipe network, and then connect and proceed. I recommend small pipes, as large pipes didn’t work for me.
I also solved it using Railcraft.
The first unloader has ethanol locked into the filter.
I think I like Tau’s pipes better.