yeah, the HD around me doesn't carry them, they told me for liablility reasons? I told them I was trying to make a rain barrel to catch water run-off, they didn't have a clue. Your local plumbing supply store will have them, the one that all the real plumbers go to. If not, just google it, you'll get a whole bunch of hits. My suggestion would be to get a bunch of them. I put them on the bottom of both reservoirs, and the tank for my RO water. I would suggest a fill valve that is adaptable to 1/4 tubing that way you always have fresh water on reserve.