Motivation: If I was going to go to the trouble of building a rain barrel, I was not going to make just any old rain barrel. No, I built the finest rain barrel system possible. Well, almost... Two barrels means the plumbing is more involved than just a spigot on a single barrel so I put on my plumbing hat....

Background:

With two barrels I wanted to be able to fully control the system - drain one barrel while the other is full, allow them to fill together, etc. So, the basic system as I have it is that water flows into the top of one barrel through an improvised "funnel" which is a large galvanized HVAC fitting to cut down from 8" to 6". I covered the top with window screening to keep mosquitos and debris out of the barrel. At the bottom of each barrel I drilled a 1" diameter hole and used brass fittings, washers and a whole lot of silicon sealant to give me a nice thread to work with. Modular is the word here. .

The picture here doesn't show the final design but it gives a pretty good idea. The washers go on either side (in and out) of the barrel, pipe runs out to a shut off valve for each barrel then to a T and out to a spigot. I didn't show the copper pipe here, just the fittings. Here's the key to the parts:

1. Brass Hex Coupling
2. Zinc Washer
3. Brass Close Thread
4. Threaded Hex Coupling
5. Female Threaded Fitting
6. 90° Copper Elbow
7. Ball Valve
8. Copper Tee
9. Female Threaded Fitting
10. Stopcock

I am concerned about ice bursting the pipes but we'll just have to see. We've had some pretty cold weather so far and the tanks haven't frozen solid yet. I'm not sure if I'd be better served emptying them down to the level of the pipe and risk ice in the pipes or leave the tanks full with the idea that 120 gallons has quite a bit of specific heat and probably won't freeze solid.

The last bit of plumbing is an overflow tube. I cut a 2" hole in the side of one of the barrels near the top. Through that I attached 2" PVC pipe and using a combination of glued connections and threaded connections (glued the threaded fittings to the pipe) I made a modular overflow pipe which runs down the back and under the stand exiting at ground level.

If you can imagine now... The water flows through the screen into one barrel. Both valves are normally open so the water level stays equal in both tanks. When they are full excess water flows out of the second tank. I'll draw diagrams and such to show this - much easier to show than explain.

Here's a more detailed picture of part of the final plumbing design where the pipes exit the barrel. The parts are as follows.

1. Rainbarrel
2. Zinc Washer
3. Threaded Hex Coupling
4. Brass Close Thread
5. Threaded Coupling
6. Ball Valve
7. 90° Copper Elbow