# Drinking water/Rain barrel

This demonstrates how to make a rain-barrel. Components of instruction will be separated so a rain-barrel can be made to the builder's preference. Hopefully, rainwater harvesting can come in handy for a rainy day or drought. The assembler and user are responsible for drinking water safety.
A rain-barrel is useful in developing nations or regions where clean water may not be available. Rain water is relatively pure, still precautions need to be taken for sanitation and health safety. Mosquito larva and other organisms need to be kept out. Bacteria, protists or other microbes can develop inside the rain-barrel, so proper heat sanitation treatment in a cooking container may be necessary before consumption.
Be mindful of: air pollution, potential acid rain, proper disinfection, maintenance, extended drought conditions including desertification, lack of minerals in water, rain collection surface and other variables. The project assembler and users of the rain-barrel are responsible for drinking water health safety and avoiding shortages.

## Common materials

* food-grade barrel or new plastic garbage can (non-cancerous made material)
* 1/2 male brass valve
* 1/2 pvc threaded coupling
* 1/2 o-rings (make connections watertight)
* 1/2 in hole-saw with guiding drill (can be used on a properly sized hex bit hand screwdriver)
Threaded fittings with o-rings eliminate or reduce the need for pipe cement. If the desired threaded fitting is not available in pvc form, galvanized or brass fittings will connect to pvc fittings. Any metallic connector should be non-lead.

## Drinking water connection

Use a 1/2in hole saw to cut a hole on the bottom side of the rain-barrel. Put an o-ring on the valve, insert it in the hole. Put on the other o-ring from inside the plastic can, then thread on the female 1/2in pvc coupling.
If plumbing is connected, prevent unsanitary conditions from backing up into or siphoning into the water-barrel: a check-valve, and precaution to keep the connected piping or tubing off the ground and away from unsanitary conditions are desired.

## Overflow

Use the hole saw to cut a hole on the side near the top of the plastic can out of the way of the lid. Put an o-ring on the male threaded coupling, then insert it through the inside of the hole, from the inside. Put an o-ring on the coupling from the outside of the lid. Put a 1/2in (faucet type) strainer inside the 1/2 elbow. Thread the 1/2 elbow on the coupling, facing it down when done.

## Additional water-barrels

Near the bottom side of both rain-barrels, drill a 1/2in hole. The water-level of the connected rain-barrels will remain in equilibrium. If the connection is made too high, the water from one barrel will not be able to empty into the other. For each rain-barrel use threaded couplings, with an o-ring on each side of the water-barrel walls. Flexible pvc tubing with appropriate connectors between containers is ideal.
Each additional rain-barrel can be made with only one hole drilled in it, because the multiple connections can be made externally with Tee or Cross fittings. This simplifies closing off the drain connection by fitting on a threaded plug, if this secondary barrel is wanted for another purpose. Two connection points per secondary barrel can be made optionally.

## Lid

Use the lid, not the can, for inflow to the water-barrel from gutters or other collection surface.

## Foundation

Rain-barrels can be upright partially below ground, or it can be on cement blocks. If the water barrel is partially below ground, the top of the water barrel must be above the highest potential flood level, to avoid sewage or other contamination, and a pump may have to be used. All connections, especially below potential flood level, must be watertight. Sand can be used for the foundation, to prevent initial shifting of the water-tank to prevent it from breaking. Once it is settled, this is unlikely to be a problem. Bricks may be built around it for aesthetic purposes, or for keeping it out of view.

## Calculating rainwater collection

Rainwater collection from roofs can be calculated using the following formulas:
* 1 inch of rain on a 1,000 square feet (93 m$^2$) roof yields 623 gallons (2358 litres) of water
* 1 cubic foot equals (12inch by 12-inch (300 mm) by 12-inch (300 mm) cube) equals 7.48 gallons
* 1 millimeter of rain on a 1 square meter surface yields 1 litre of water.
* 1000 litres = 1 cubic metre. 1 cubic metre of water weighs 1 (metric) tonne.