Move Water with Water

Image Gallery iStockPhoto.com/Nico Smit

You might have heard it if you’ve ever been on a farm – the soft and steady “thunk, thunk” can be mistaken for the beat of a drum. It might have been unsettling for you until someone explained that the sound’s source is a ram pump, sometimes and understandably referred to as the heartbeat of a farm. What exactly is this device that seems to defy gravity by moving water up hills with nothing more than the power of water?

The ram pump is, quite simply, an air-breathing invention that supplies water to your house, livestock and garden 24 hours a day, 365 days a year. It’s done without the help of electricity and only a couple of moving parts. It’s ingenious, and it has saved the backs of humans for centuries.

How it works

Unlike many pumps, the ram pump is not immersed; it needs air and a water supply to operate. The water source can be a creek, river, spring or pond as long as the water intake is located upstream (at a higher elevation) from the collection point at the pump. Water (from the source) travels down the drive pipe to the pump, where, with the help of a flow-actuated check (clack) valve, the flow is intermittently stopped and started. Thanks to the physical laws relating to inertia, abruptly halting flow in the drive pipe causes the water column to behave a little like a hammer. That hydraulic hammering then forces about 15 percent of the water through a one-way check valve and into an air-filled pressure tank, which in turn feeds the delivery line. The remaining 85 percent of the water flows through the clack valve when it drops open (see illustrations, Page 49). Once the flow gets back up to speed, it slams shut once again, and the process repeats itself several times a minute to deliver a steady supply. As long as water flows, the ram pump won’t freeze.

The ram pump’s process is wonderfully perpetual, but small things can interrupt the rhythm. For example, a small clog in the source’s drive pipe can reduce flow enough that the clack valve won’t close, thus shutting the pump down. With a little care, you can keep the frequency of ram pump outages well below electric service outages, which will render most other water supply pumps idle.

Plans for the ram

English inventor John Whitehurst is credited with inventing the ram pump in 1772, although his invention’s valve was manually operated. Opening and closing the valve was easier than some other means of moving water, but his pump never really caught on. Twenty-four years later, French inventor Joseph Montgolfier modified the design and created the automatic ram. The ram pump made it to the United States in the 1840s and was immediately embraced by farmers and others with a need to move water more easily. The device was especially popular because its constant fresh water output prevented frozen water tanks.