First, I used to think it would be nice to have a lot of catchment in one place, with either one large cistern that could hold a 1000 gallons, or a row of tanks. And indeed I've even had a couple of largish tanks linked together in places. What I've found, though, is that I prefer to have single tanks set up strategically at each corner of the house, as it makes delivering the water to the garden an easier task. Also, the tanks are not huge (two 50 gallon and two 100 gallon), but I have found that they are sufficient for supplemental watering. My goal is to have the landscaping part of the garden need only occasional watering during extreme drought. I'm hoping that the rainwater I collect and store will be enough to allow me to go completely off the city water grid in the next couple of years (for the purposes of landscaping or gardening). In other words, I am planting things I expect to survive under desert conditions, and as such, any irrigation that might occur would merely be a friendly boost.
Here is my set up at present:
Two in the front, where they blend in nicely with the landscape:
And two in the back (though I'm only showing one here, as the other was temporarily decommissioned in order to install some siding, and I haven't gotten it back on line yet):
First, I elevate the tank, to make it easier to attach hoses and fill watering cans:
I wait until the gutter guy installs the downspout and I can see exactly where the opening will be, then I cut a hole in the top and attach a gutter splash guard. You can find these at the hardware store in the rain gutter supply section:
I then attach mosquito screen attached to the underside of the lid. I staple the screen about two inches from the edge, so that when the lid sits on the top of the tank, it drapes over and creates a seal:
If the lid is going on one of the larger tanks, I make a hinged section, as demonstrated below by my neighbor Karen. This makes it easier to check the quality or level of the water, perform any needed maintenance, or fill a watering can.
I attach a no-kink hose bib to a three-inch long, 3/4" galvanized pipe. Some tanks come with a 3/4" threaded opening, and others do not. If it does not, the pipe can be installed by using thin nuts, as seen in these two photos:
I cut an opening for an overflow tube using a step unibit, which can be found on Amazon for a very reasonable price.
At your local Bog Box Hardware, you can find swankier versions of these in the electrical contractor section of the hardware store, where they are usually kept under lock and key to imply that you need to pay an arm and leg for them. Don't ask me how I know this.
You might as well order one now from Amazon so that it will be ready for you to use on your new tank. Go ahead, I'll wait.
The overflow tube is a flexible tubing also found in the electrical section. It has two threaded ends, and comes with gaskets, nuts, and couplings that screw on. These make it easy both to attach the tube to the tank, and then a hose to the tubing:
Though the nut makes the coupling is unnecessary to attach the tubing, the coupling comes in handy for another reason, since I can cut a small piece of screen and place it inside it to keep mosquitoes from making their way into the take via the overflow tube. IT IS VITAL TO SCREEN EVEN THE SMALLEST OPENING TO PREVENT MOSQUITOES FROM BREEDING.*
You can also attach screening like this:
And there you have it, the tank is now ready to go.
Here are some earlier posts on setting up connected tanks that you might also find useful. In them, I use a different tool for cutting the opening, but it is even more ridiculously expensive than the unibit from the Big Box, so unless you have an electrical contractor friend, don't even try it.
Now I'll show you mine
Rainwater Harvesting: Making the connection
Rainwater Harvesting: Putting a lid on it
*From time to time, people suggest that I put mosquito dunks in my tanks, and I have done this in the past. In my experience, however, they just don't seem to work. Instead, I find that being extremely diligent about closing off openings is much more effective. So don't get lulled into thinking that you can just drop in a dunk and slack off on this vital part of the construction. Think like a mosquito! Be the mosquito! Find those openings and then close them off.