THE RAM PUMP
by Steve Herbert
Imagine a device which would pump water automatically, night and day, without power by virtue merely of its own design, and to heights far exceeding the level of its source. Such a device has obvious utility, especially where electrical power is non-existent, and is know as the ram pump. With sufficient head and properly installed, the ram pump can feed irrigation ditches in remote areas or fill cisterns or storage tanks for communities or residences.
The basic design of a ram pump consists of a declined feed or drive pipe carrying water from a source above and delivering it to a chamber within the pump. Power for the system is hydraulic, generated by the weight and velocity of the water within the declining drive pipe, which in turn is a function of the pipe’s length, angle and diameter, as well as the flow within. Upon entering the pump (see Figure 1), the water takes a path of least resistance through the Outside Valve until the force of the water builds to the point where the Outside Valve is prompted to close. At this point, the pressure of the water is enough to open a check valve called the Inside Rubber Valve, and the water enters the Air Chamber. In the time it takes for the air and water pressure within the Air Chamber to equalize, a small amount of water is forced into the delivery pipe, against the resistance of the water already in it. Described another way, the air in the Air Chamber is compressed, and when it begins to push back it closes the Rubber Valve as it pumps out some water.
The resistance of the water within the delivery pipe is also determined by the incline, length and volume of the pipe. Velocity here is not a factor, and that is why the water entering the delivery pipe can momentarily overcome the resistance of the water standing in the pipe. Once the force of the water exiting the pump has done its work, it can no longer resist the backpressure of the standing water. At this point, the flow in the drive pipe momentarily rebounds while a small amount of air is simultaneously sucked into the upper section of the base through the Air Feeder Valve. This small amount of air is added to that already in the Air Chamber on the next cycle, helping to replenish any lost during the last and preventing the pump from becoming waterlogged. The water in the drive pipe then reverts its flow through the Outside Valve, completing the cycle.
How much yield is produced at the point of delivery depends on many factors. The pump itself comes in many sizes. Flow can vary with the number of cycles the pump repeats within a standard amount of time. Normally, however, one can expect a frequency of from 25 to 100 repetitions per minute. With each repetition, more water bypasses than is pumped. In fact, depending on many factors, which include mainly vertical fall of the intake pipe and elevation of the delivery pipe (see Figure 2 or 5), the amount of recovery may be as little as 2% while very unlikely to surpass 22% (Rife has a table for this on their website: www.riferam.com/rams/ramwaterdelivered.html). Any installation will have to provide means for the drainage of this bypass water.
To install your ram pump system, you will first have to gather certain information and measurements. To begin, determine the flow rate of the water at the source, measuring in gallons per minute. For a lower flow, you may record the amount of time it takes water from a pipe to fill a bucket or container of known capacity. It is best to make this measurement at the driest time of year, so that you will know the minimum flow to expect (see Figure 3). For a higher flow, you may construct a “weir”. A weir in this case is a board spanning the entire width of the stream, having a rectangular notch of known width in inches (see Figure 4). The bottom of the notch should be level with the stream bed. To determine the height of the water, take the measurement at least two feet upstream form the notch. With the height and weight determined, you can go to Rife’s website to compute the number of cubic feet of water that will pass per minute from a table (www.riferam.com/rams/raminforeQ.html). You may convert to gallons per minute by multiplying by 7.5. This information will be used to determine what size pump to buy.
Next you will need to determine the vertical Fall and vertical Elevation, in feet. The vertical Fall is the distance from a point level with the source down to the planned position of the pump (see Figures 5 & 6). A cord and line level with a measuring tape should be all you need to determine this, or a carpenter’s level on a stick with known length (see Figure 5). The greater the amount of fall you can create the better. There is a direct relationship between amount of fall and amount of water that will be pumped. In other words, twice as much water will be pumped with a fall of 6 feet as with a fall of 3 feet. The vertical Elevation may by too great to be practical to measure with a cord and line level, in which case you can use the level on a stick method. Rife’s website advises you to start at the lower level and work your way uphill.
The final measurements you will need are the horizontal distance between the water supply and the pump, and between the pump and the point of delivery. The former will have to be matched to a compatible length of Vertical Fall. In other words, for a Vertical Fall of 3 to 15 feet, the length of the drive pipe will have to be six times the length of the V.F. For a Vertical Fall of between 16 and 25 feet, limit the length of the drive pipe to four times the length of the V.F. If the Vertical Fall is anywhere from 26 to 50 feet you are confined to a drive pipe length of three times V.F. The length of delivery pipe is not as critical.
There is also a minimum and maximum recommended length of the drive pipe, based on the pipe diameter. The rule is that minimum length should be at least 150 times the pipe diameter, whether it is expressed in inches or millimeters. Maximum length should be no more than 1,000 times the pipe diameter. For example, for a drive pipe of 1 ¼” diameter, it should be a minimum of 187.5 inches (15’ 6’’) and a maximum of 1,250 inches (104’ 2’’).
If the maximum length is exceeded, then a vertical standpipe may be installed on the inlet pipe at the point of maximum length. This helps the pipe withstand the shock wave pulsing through the water back up through the drive pipe. If the pipe is too long, the shock waves will not have enough time to dissipate and will interfere with the pump’s rhythm. The standpipe should be of length to reach at least one to two feet above the source water length. This pipe should not shed more than a few drops of water out its open top, and be two or three sizes in diameter more than the drive pipe. The excess drive pipe above maximum length should be one size larger. An open tank installed at this point on the line could serve the same function.
You will also need an idea of the amount of gallons which will be required per day to meet the need. The formula for determining the amount of water which will be delivered (D), is Flow in gallons per minute (V) times the vertical Fall in feet divided by the vertical Elevation (F/E) times 0.6 (an efficiency factor); D = V x F/E x 0.6.
There are several tips which could be offered regarding installation. It is recommended that the feed or drive pipe be metal, preferably galvanized. If PVC pipe is to be used, it is best that it be schedule 40 and encased in concrete, or very well anchored at the least. Either way the drive pipe should be watertight, naturally, with a filter screen at the intake end to prevent debris from entering. The pipe should be straight without elbows. Rigidity of the drive pipe helps pumping efficiency. If buried in a ditch, the drive pipe in temperate climates should be buried at least four feet to protect from frost (see Figure 6). The amount of fall will determine more or less the optimum length of the drive pipe (see the table on Rife’s website: wwwriferam.com/rams/raminstall.html). The size of the drive pipe (and delivery pipe) should match the particular size pump you order. Efficiency will be reduced due to friction in a pipe too small.
The pump should be placed on a solid foundation such as a concrete slab or large flat rock and bolted down. Either way, it should be set in such a way that a slight declination toward the back allows bypass water to drain. A pipe to direct this water away should be included in the installation. The base should be of such dimensions that it can serve as a footing for surrounding walls to protect from damage, freezing weather or theft. A ram pump needs a minimum of 18 inches clearance all around to allow room for maintenance. Walls also need to be high enough to protect from flooding. A roof should protect the pump from weather, especially in temperate zone winters, but allow access for a person to inspect or repair.
Bypass water can be directed away by either pipe or tile. If the pump is strategically placed, unused water could be directed back into the stream further down. Otherwise, the advice is to create a reservoir for containment. The pipe which directs the water here should end at the bottom of the reservoir with a sleeve joint. An upright pipe attached to this should be long enough to end above the level of the reservoir’s emergency overflow.
In the event that the ram pump needs to be disconnected or removed for repair, gate valves in drive and delivery pipes facilitate the job. Should it not be possible for the delivery pipe to have a straight and gradual incline to its terminus, it would be necessary to install valves or petcocks at the high points to periodically release accumulations of air. Rife can be contacted for advice on this or any other special circumstances. They have all pumps and their respective parts in stock, and can ship out orders usually within a business day to anywhere in the world.
A ram pump may also be home built, using parts readily available at a hardware or plumbing supply. Plans are also available on line, sometimes for free. The various parts can be either metal or PVC, but sometimes a combination provides the best balance between maximizing durability and minimizing weight.
In our series of articles about appropriate pumping technologies, all have involved manual operation. The ram pump now makes an exception in that with proper design and set up the water is induced to pump itself. Such a system can be readily purchased, but can also be homebuilt. Thus it fits the definition of appropriate technology; being operated, maintained and repaired within the capacity of rural farmers with available parts in a project within financial reach. Where surface water sources and gradients allow, this can be a great blessing.
John Whiteburst of Derby, England, built the first prototype “hydraulic machine” in 1775. However, it was a French inventor by the name of Joseph de Montgolfier in 1797 who greatly improved the design and is considered the father of the hydraulic water ram pump. It was first brought to
Figures were used by permission of RifeRam.com.
Clemson University Cooperative Extension Service (home built plans)
Green and Carter
The Ram Company