X10 is a very unreliable protocol. It is a one way communication with no error or control or confirmation signaling. You could certainly setup something that will work, but will it be reliable enough to trust?
You would be much better off just using digital timers directly but even at that, I a, not a big fan of dosing using anything but fixed displacement or metered pumps. Peristaltic pumps can be had fairly cheaply on eBay and are much better candidates (more consistant).
Bean