I've been having a lot of fun with these RO media housings. First I built a kalk reactor out of one and now I've made myself an effluent chamber. For this all I did was drill and then tap a hole near the bottom of the housing. I cut some egg crate to fit at the bottom to create an empty space and stuck a circular cut up piece of filter sponge on top of that. I also plugged one of the outfeeds at the top of the chamber. I've been running this creation for a few days now and I've tested the water coming out of the effluent chamber to be .4pH higher than what comes out of the reactor.