Step 1: Drill three of four holes in the barrel. One of these is for the bibet to connect your garden house to the barrel and the other fittings will allow you to add more barrels in the future. One of the barrels must have an overflow fitting near the top of the barrel. If you plan on using 3/4 inch fittings use a 1 inch hole saw to cut the holes. If you have an adjustable hole saw make it a little smaller than 1 inch.
Step 2: Place plumbers goop on a 3/4 inch nipple. Using a 3/4 inch galvanized metal nipple and some locking pliers, thread nipple into the barrel. the hole for the fitting. Place Plumbers goop or some other adhesive on the thread.
Step 3: Now the real fun part. Cut the down spout at the proper height. You should place the rainbarrel on one or two concrete blocks and then determine the proper height. After cutting the down spout attach the necessary elbows and extensions to have the down spout reach the barrel. I still am trying to create a non ABS or PVC way to divert the first couple of gallons after each rainfall (this will keep the sediment from clogging up the screen). Attach a 4 inch by 2 inch ABS plastic converter to the end of the down spout and attach a fine mesh screen over the converter (you can use a paint sprayer filter which you can get at a hardware store).
Step 4: If you are adding more barrels do this now. Attach a garden hose Y fitting on the 3/4 inch nipples. Position the barrels on top of the concrete blocks and cut the right length of garden hose to connect the barrels (with male fittings attached to both ends).
Step 5: The final product. You must attach an overflow line on the first barrel (the one on the far right in this picture). This must be placed near the top of the barrel and it should be attached to some form of hose or tube to discharge any overflow. Please note that you must remove one of the two bung fittings on the top of the barrel and cover it with a small screen. I used the paint sprayer filter with a rubber-band to hold it in place.
Further reading & source: http://www.rwh.in/howto.html
Complete rain barrel construction kit: https://gardenwatersaver.com/product/rain-barrel-kit-3×4/
Last updated on 23-May-2022.