It can be easy to transform an oak barrel into water feature, especially if you start with the right kind of barrel. Many garden stores and home centers offer half-barrels from vineyards and distilleries. The chief advantage to these barrels is that they are built to hold liquids, which gives you a head start. From there, creating a water feature is a simple matter of assembling the parts correctly.
Working outside, fill the barrel with hot water and let it sit. The staves may have shrunk while the barrel was stored, but the hot water will swell the wood so the barrel is watertight again. Remove the water after four or five hours.
Center the brick or paver stone in the bottom of the barrel. Set the submersible pump on top of the brick or stone. Route the cord up the side of the barrel and out. On the outside of the barrel, mark the approximate height of the top of the pump.
Attach the clear plastic discharge tube to outlet valve on the submersible pump.
Add water to the barrel until the water level is several inches higher than the top of the pump.
Fill the barrel with river rock, being careful not to knock over the pump. Place large rocks at the bottom and leave plenty of room between the rocks. The pump needs constant access to water. It will flow down to the pump if you leave gaps between rocks. Make sure the top of the discharge tube is still visible after the rocks are in place.
Attach the fountain head to the discharge tube. Most of these heads simply fit down into the tube.
Plug in the pump to an outlet protected by a Ground Fault Circuit Interrupter. The water will spill out of the fountain head and down into the barrel, where it can be recycled by the pump. Check the water level every two days or every day in extremely hot weather.