Intro: Rainwater Catchment... Cheap & Simple!
This is a cheap and simple way to create a rainwater catchment system. It takes about an hour from start to finish, the only tool I used was a utility knife, and it costs under $15. Hopefully this project should be accessible to just about everyone. This is a good project for city dwellers with limited space or renters who aren't allowed on the roof, or don't have access to an outdoor hose...
•your favorite utility knife.
•a large container to act as the cistern. I used a rubbermaid tub gleaned from the street in front of our house.
•garden hose: the amount will depend on how far you'll need the water to travel for your gardening needs. Mine is 30'.
•a nozzle or valve for the watering end of the hose.
•gaskets or gasket material: some gaskets came with my hose, I used a bike inner tube for the rest.
•pvc threaded fittings: we're looking to trap the wall of the cistern tightly between gaskets at the point where the hose is attached.
•something to filter the rainwater and prevent evaporation. I used a coffee bag.
•a rope or bungie to tighten around your cover.
Step 1: About the Fittings
You'll need two fittings: a threaded 'male' one for the inside of the tank, and a 'female' for attaching the hose to the outside. Again, we're sandwiching the tank wall between these two threaded fittings, and sealing it tight with gaskets on both the inside and outside. You'll need to make sure everything fits together before you leave the hardware store- mine had a rather limited selection, but if you have more choice, choose fittings that have more material supporting the sides of the cistern.
Step 2: Drain Placement
It's time to decide where you want the drain. You might want to put the drain at the lowest point to make the most of your water, or you might live in a windy place and want to leave some water in the tank to weight it down. If that's the case, position your drain a bit higher- but remember, water is very heavy.
Either way, the fittings and gaskets need to be seated flush against a flat surface, so make sure you're not positioning your drain on a curved corner of your tank.
Trace the fitting but NOT THE THREADS- you want the fitting to be threaded tightly through the drain hole. If the drain is the right size, you'll have to apply pressure and screw in the fitting.
Step 3: Cut Out the Drain Hole
Make a small 'x' shaped incision in the center of your traced circle. Cut the flaps out so you have a square hole, and carefully carve out little tiny shavings of plastic until you are nearing the edge of your traced circle. At this point you might want to bust out the file on your utility knife, if it has one. If not, go slowly and gently, shaving off little curlicues of plastic rather than big chunks. Be careful not to cut yourself or make the hole too large. Remember, you want to have to really work to thread the fitting though- it should be very snug.
Step 4: ... the Inner Fitting
It's time to put the first fitting in the inside of your tank. Put one of your rubber gaskets on the threads. Then screw the fitting through the drain hole you've just made. You want the gasket to be extremely tight against both the fitting and the wall of the tank- but remember, you're working with plastic which will stretch or crack if you apply too much pressure. Go slowly, and try to pay attention to how the material is responding. It should look something like the photos...
Step 5: Gasket for Outer Fitting
If your hose didn't come with gaskets, you might need to make some. Bike inner tube is perfect for this, but any softish rubber sheet will work. I cut out a square, fold the square in half, and cut out a smaller hole than the gasket should be. Then open the thing up and make some more slow and careful cuts until you have a circular hole slightly smaller than the unthreaded diameter of the fitting that's now poking through the side of your tank. Once you've got the outer gasket on, screw on the 'female' outer fitting as tightly as you can. It's a good idea to make sure the inner one is still tight, or tighten both of them against each other at the same time.
Step 6: Attach the Hose! and Cover.
This is pretty self-explanatory, but... screw on the hose.
Then, take whatever you're using for the cover and secure it around the edge with a bungie. Local coffee roasters are a great source for free burlap bags. You're looking for something permeable, light in color (so it won't get too hot in there) and with a small enough mesh so mosquitos can't get in to breed.
Step 7: 'install'
Put your catchment bin wherever you need it to go. In our case, we have a slanted roof above our garden that was well situated. You can always put a few bricks under one side to give the bin better water flow, or if you're worried about wind set up the bin so there's always some water to weight it down. Ideally, you could run a section of garden hose from your gutter into the bin for more efficient catching. Remember the weight of water! A cube of water 3' x 3' x 3' weighs nearly 1,700 lbs, so make sure the structure you're putting the catchment cistern on is strong enough to support it safely.
Now check your forecast & hope for rain!