How to pump water without electricty!
A few years ago, I was asked about how to pump water in an off grid situation. Luckily, I was doing some research about this kind of topic and it piqued my interest. I found out about a little thing called a hydraulic ram pump or just a ram pump for short. The mechanics of the little pump is quite amazing with only two moving parts! It’s a pump that uses hydraulics to pump water without using any electricity. It will take water in and waste almost 85-90% of the input water as the source of energy to pump the last 10-15% of water. For every foot of fall, you can expect 7 feet of vertical lift!
Step by step
- Look at the ball when it is in the lowest position.
- Water flows in with a high velocity at “water in” feed pipe or drive pipe as we will call it.
- The water flows out at “waste water” but at the same time it pushes the ball up the curve.
- When the ball hits the top point, it blocks the water flow and a short impulse builds up behind the ball.
- The impulse presses a little amount of water through the one-way valve at very high pressure.
- The impulse is very short and as air can be compressed very fast, the air in the chamber acts as an energy buffer.
- The one-way valve closes again holding the pressure in the chamber.
- The air pressure pumps the water out through the “water out” delivery pipe.
- The ball is forced up by the water flow, but because the flow stopped, it rolls back to the lower position.
- The cycle then begins again. This cycle duration is between 1 and 2 seconds.
If you have either a deep or shallow well, this pump will not work for your situation. But, if you have a way to funnel water from a source, and it is able to flow down to your pump, then you might be able to use a ram pump. A stream, river, pond or above ground spring are all good options for using this type of pump. Every situation is different, but there is always a work around for these small challenges. So lets take a look at each section of the pump site to get an idea of what is needed, and then break them down to fully explain each.
In the above schematic, there is a settling reservoir and collection tank before the drive pipe. These are not needed, but can be a good idea to add to your system depending on your situation. If you have very muddy or silty water, a settling reservoir would help to clear up some of the debris in the water and help out in the filtering process much later. The collection tank would help for situations where the water source isn’t constantly flowing or fluctuating.
First, let’s talk about the drive pipe. This is one of the most important parts of the pump. This is the source where the pump will get its power and the precious commodity that you are trying to capture. The drive pipe should be as rigid and as straight as possible. Diameter size and length of the drive pipe is critical to making this pump work. The diameter of the drive pipe has to be double the size of the delivery pipe. So for example: a 2 inch drive needs a 1 inch delivery pipe or a 1 inch drive pipe needs a 1/2 inch delivery pipe. To calculate the length needed for the drive pipe to properly drive the pump, first find out the height of fall. This is measured vertically from the top where the water first enters the drive pipe to the bottom where the water would go into the pump. An easy way to measure fall is to have a level on the top of a measuring stick or string and measure each section of the drop until you get to the bottom.
- For up to 15 ft of fall, drive pipe needs to be 6 times the fall.
- For up to 25 ft of fall, drive pipe needs to be 4 times the fall.
- For up to 50 ft of fall, drive pipe needs to be 3 times the fall.
If your drive pipe is longer than these preferred distances, you may need a stand pipe. A stand pipe acts as a small collection tank to help control the flow of water and the pressure of the water going into the pump. If the drive pipe is too long, the water hammer shock wave will travel farther, slowing down the pumping pulses of the ram. Also, in many instances there may actually be interference with the operation of the pump due to the length of travel of the shock wave. The stand pipe simply allows an outlet that is open to the atmosphere to allow the shock wave to release or dissipate. Remember, the stand pipe is not necessary unless the drive pipe will have to be longer than the recommended maximum length. This stand pipe will need to be slightly taller than the water source of the drive pipe, because it will fill up to this level. Also, install the stand pipe at the point where the preferred distance is suggested to reduce the height that is needed.
The delivery pipe can be made out of anything and isn’t affected by the pressure coming from the ram pump. The only thing that is important for the delivery pipe is, as stated above, the diameter is half of the drive pipe. This allows the pressure to build up behind in the delivery pipe causing the one-way valve to close and pressure to build in the air chamber.
As for the build of the ram pump itself, I’ll leave that to Engineer775’s How to build a Ram Pump video. The parts can be purchased from any hardware store or on-line for about $150 in parts if made with brass or even cheaper if made with PVC.
Don’t expect the flow rate out of this pump to be massive. It will be anywhere from a small trickle to a continuous pour. The ram pump doesn’t deliver pressure but it makes up for it in the amount over time. Keep this in mind during the build so that you can have a collection tank large enough to handle the usage for a whole day. To find out how much flow you should expect to get out of the pump:
Q x F / E x 0.6 = D x 1440
(Volume of Flow) x (Fall of Drive Pipe) / (Elevation of Consumer Tank) x 0.6 (Efficiency of pump) = (Amount Delivered Gallons per minute) x 1440 (minutes in the day to get gallons for whole day)
To find out how tall you need to build a water collection tower:
Desired PSI x 2.31 = Elevation in feet
- Example: 10 PSI x 2.31 = 23.1 feet above where to water is to be delivered.
Still interested in building a ram pump? A few last points:
- Make sure you place a strainer on the drive pipe because you don’t want to get anything in the pump to clog it and keep it from working.
- Anchor the pump because the hammering action in the valves cause the pump to vibrate.
- Plastic pumps are limited to very low delivery heads, metal pumps can handle much higher pressures and pump to higher heights.
- Make sure the waste valve is vertical. If it is tilted, it makes the pump not very reliable and it will not pump as much because the valve doesn’t open and close as reliably.
- Ram pumps can be scaled to any size!
Sounds too good to be true? Well, as with any thing, there are some problems with the ram pump. They include:
- Failure to deliver sufficient water may be due to improper adjustment of the waste valve, having too little air in the pressure vessel, blockage of the valves with debris, or simply attempting to raise the water higher than the level of which the ram is capable.
- The ram may be damaged by freezing in winter, or loss of air in the pressure vessel leading to excess stress on the ram parts. These failures will require welding or other repair methods and perhaps parts replacement.
- It is not uncommon for an operating ram to require occasional restarts. The cycling may stop due to poor adjustment of the waste valve, or insufficient water flow at the source. Air can enter if the supply water level is not at least a few inches above the input end of the supply pipe.
- Improper installation, such as using a supply pipe of non uniform diameter or material, having sharp bends or a rough interior, or one that is too long or short for the drop, or is made of an insufficiently rigid material. A PVC supply pipe will work in some installations but is not as optimal as steel.