Have a spring or flowing stream on your property? You may have a source of running water that you can use for irrigation. A ram pump is a low-cost solution for pumping water without electrical power since it uses the kinetic energy from flowing water. This old technology utilizes the momentum of falling water to power a pump using two valves to generate a water-hammer effect. Ram pumps take their name from the noise they make when water under pressure comes up against a closed valve.
For the pump to work, water must fall at one flow rate and output water (at a higher pressure) at a lower flow rate. The pump needs a water supply from an elevated source and a delivery pipe that provides a drop of 1 foot for every 5 feet of length from the water source. This source pipe needs to be full of water at all times.
The pump has only two moving parts, a primary (waste) valve and a secondary (check) valve. The momentum of the water in the delivery pipe builds to eventually close the primary valve. This causes a water-hammer effect that forces water back into the delivery pipe and into a pressure tank. The pressure tank absorbs the hammer shock and improves the smooth flow of water in the delivery pipe.
Due to simple gravity, the water velocity in the delivery pipe builds up to close the primary valve (1) in the bottom chamber (see drawing). Water is then forced into the pressure tank (3) and through the one-way secondary valve (2), compressing the air in the tank. The air pressure increases, forcing the water back, closing the secondary valve (2) and sending water into the delivery pipe/faucet.
Meanwhile, the pressure drops in the chamber beneath the primary valve, forcing it to open (1), and this pressure relief allows the water in the delivery pipe to fall again. It builds up velocity flowing into the bottom chamber, starting the cycle again. This is not a perpetual engine model. The energy efficiency is around 70 percent. The amount of water delivered is related to the ratio of the source head to the supply head. For example, if a source is 5 feet above the pump and the water is pumped 25 feet above the ram pump, then 20 percent of the supplied water would be reduced to 70 percent of 20 percent (about 14 percent), with the remainder being spilled by the waste valve. While not super efficient, remember that this ram pump can be running 24/7.
Boise Pont’s Lessons Learned
“I started building my first ram pump after seeing an article in a magazine about how to build one. I thought it would be neat to have our creek pumping it’s own water to our garden and the rest of our property. I didn’t have all of the materials listed but used some that I already had on hand.
“I used an old, small air tank for the air chamber and another smaller air tank for the impact chamber, a rear leaf spring from a car for the clapper spring and 30 feet of 3-inch steel pipe for the delivery. The valves I made from steel plate. For tools I used a welder, a cut- ting torch and some wrenches.
“I put this thing together and installed it in the spring of 1978, and it worked right off, pumping water to my garden. But it stopped working after a while. It was losing its air in the air chamber. Without air, the force of the water was impacting my pump like a jackhammer. Eventually, there was no air in the air chamber and the pump would stop working.
“I decided to build another one that would add air to itself while running. This time I used a small air tank and common galvanized pipe. I placed the secondary valve higher than the primary valve and drilled a very small vent hole in the standpipe, under the secondary valve, so the pump would sniff a bubble of air with every stroke of the clapper valve. I built it and it has worked great, pumping water and air for itself. It has run two sprinklers, 24 hours a day, wherever we need it, for several years.”
RAM PUMP LINKS
To learn more about ram pumps and how to calculate if a ram pump will work at your site, visit these excellent websites: