This is a very preliminary dry fit for the plumbing of my water mixing station- not everything is cut exactly to size and I need to exchange the threaded fitting on the bulkhead of the left barrel, but I'm on limited time today. I'll make it all pretty and even this weekend. What I want to know is whether I have all the fittings where they belong. Do I have the unions and valves in the right places? Am I missing anything? The end goal is to have the right barrel fill with RODI, be able to pump it over to the left barrel, circulate and mix the saltwater, and be able to pump either RODI or saltwater as needed out the barbed fitting. And here's some novice plumber questions. Do I glue the pvc pipes into the unions, or by screwing them tightly enough, they don't leak? Also, on these threaded fittings on the barrel bulkheads (preinstalled) and the pump intake/output, do I need to use something like thread sealant, glue, or that plumber's tape? Thanks, guys! I know I've been asking a lot of questions lately, and I really appreciate how helpful everyone has been. I'm probably within a few weeks of being able to kick off build thread!