Compressed Air Well Pump and Pressurized Home Water System Bubbles – Part 1, by H.W.

There have been many great articles and letters on SurvivalBlog recently regarding alternative, non-electric, or low power well pumps. I’ve built an alternative well pump that runs on compressed air. It does require electricity to compress the air, but an air compressor can be run off a modest solar/battery rig easily and can pump a decent amount of water suitable for an emergency situation. I’d like to describe how I built this pump and how it works.

First, let me say that there are various air-operated pumping systems out there, including variations of this one; there are also some you can buy off the shelf. This is not my original idea, and you should take a look at videos of what others have done, including simpler air lift pumps. However, this pump work well for my well, which is too deep for a surface hand or electric pump with simple drop tube, and it would be rather expensive to install one of the higher quality deep hand/electric pumps, like Simple Pump or Bison Pump. I was looking for something I could build and not break the bank as well as something I could power from my solar setup AND not have to send my wife out in the snow to hand pump a bucket of water for my morning bath.

See the drawing of the well pump:

Pipe and Fitting Material

This pump is made from PVC pipe and fittings, and the lines are PEX tubing. When purchasing PVC materials for water supply applications, be sure to look for the “NSF-PW” marking, meaning the products can be used for potable water. Some PVC is marked for drain and wastewater use only. The PEX tubing should be rated for water supply applications. If you are squeamish about using PVC in your water system, you can make the pump out of copper pipe and fittings. When purchasing brass fittings for potable water use, be sure they are marked “lead free”.

Interesting Story About Toxicity

I selected a brass valve off the shelf at a big box home improvement store and took it to the checkout. The bar code would not register the price, and the clerk did some digging and told me that the part was being recalled because of high lead content! Thank you, China. At least they caught it, but what about the other 20 valves I’ve purchased over the years? At least after the crash we won’t be importing as much poison from Asia.

Pump Phases of Operation

This air operated pump produces water in bursts, and the air must be cycled on and off at regular intervals of two or three times a minute. Being an electronics guy, I built an automatic, timed controller using some 12-volt solenoid valves I purchased off of ebay, but you can easily use ball valves and cycle them manually. Filling the water tank is something that your kids can learn to do, as there’s no way to unintentionally hurt anything. Turning a couple ball valves takes a lot less sweat than pumping water from 200 feet down with your arms or feet!

There are three phases to the operation of the pump. The first phase fills the pump with water. The lower check valve opens (see diagram) and the pump and PEX lines fill with water to the static level in the well. This is the normal condition of the pump and water when it is sitting idle. To get the pump to fill, the air line is opened to atmosphere. The water line is always open to atmosphere above ground.

The second phase involves closing the atmospheric vent in the air line and then gating the compressed air into that line. The compressed air pressurizes the system, forcing water out of the pump, up the other line, and into your tank, bucket, dog dish, or long-term survival hot tub.

The third phase starts when the pump empties and some air starts coming out of the water line. The pump valve is closed, and the remainder of the water/air mix is allowed to dribble out as the system depressurizes. The check valve in the water exit pipe inside the pump prevents any remaining water in the line from draining down into the pump again, to avoid pumping the same water multiple times. This check valve could probably be eliminated, with some energy waste resulting, but I have not tried this.

The cycle then repeats.

Water Pump Speed and Durability

The amount of water pumped per burst depends on the volume of the pump body and PEX lines below the static water level. My pump is about 30 inches in length, but it could be made almost arbitrarily longer. I get about a half gallon a minute of flow.

I have dropped my two-inch diameter pump into the well beside the existing water and electrical line in the six-inch well casing. You can adjust the diameter and length of the pump to be compatible with your setup. The hexagonal plastic caps on the end of the PVC pipe make the pump about three inches in diameter.

For the air supply and water lines, I use half-inch PEX tubing. The pump is quite light, and I can install and remove it by myself at a depth of about 125 feet. The PEX tubing is pretty difficult to work with because of the coiled set it takes when rolled hot at the factory. You won’t want to be working with it on a cold day! I’ve not had much problem on warmer days, but it’s still pretty stiff. When putting the pump down the well, I use a bucket of bleach water and a rag to wipe down the tubing as it goes into the hole, to avoid introducing surface contaminants into the well water.

The compressor I use is a 20 gallon / 2HP unit from a discount tool store. It runs fine in this application. The pressure regulator is adjusted for about 50PSI. I tried a small pancake compressor, but it simply does not produce the volume of air required to pump much water. Think about it. If you want to pump 100 gallons of water, you’ll need to push at least 100 gallons of air through the pump. My solar setup consists of about 500W of panels, a charge controller, and a large truck battery; it’s nothing fancy or expensive. A 2000W inverter runs the compressor nicely.

In the drawing you will see an eye bolt on the top of the pump. The PEX tubing is plenty strong to drag the pump up out of the well, but just to be sure I attached a one-eighth-inch, plastic-covered, wire rope to the eyelet and to a matching eyelet on the underside of the well cap. If the tubes come loose for some reason, I can still fish the pump out of the hole.

My well casing is steel, and the inside of it is quite rusty. It takes some force to shove the pump and PEX tubing down the hole. You need to be careful that there are no outside parts of the pump that can wear and be damaged as you do this. A PVC well casing would not be so rough.

For water connections at the surface, I put brass fittings on the well cap, rather than digging down and cutting a hole in the side of the well casing. I bought a new well cap to use, as they are pretty inexpensive, and I kept the old one as a spare. The PEX tubing is attached to the brass barbs on the underside of the well cap, with hose clamps securing the connections. I used a torch to heat the PEX a bit before pushing it onto the barbs and tightened the hose clamps before the tubing cooled. The tubing is now conformed to the barbs and won’t be coming off any time soon.

Since the water lines come out of the top of the well cap (parallel to the ground using right angle fittings), they are subject to freezing in the winter. However, both lines are filled with air when idle. You can run the air compressor for 30-60 seconds to blow the air lines dry at the end of your pumping session. In that way, the lines do not freeze closed. The water coming out of the well runs about 50 degrees year round and warms the lines in freezing weather. Our lowest temperature in the winter is typically in the teens, so you might have to bury the lines completely if you live in a colder clime.

The PEX lines are run underground to the house through the concrete foundation wall. PEX is rated for burial, but rocky dirt might be a problem and require a sheath, which could simply be some more PVC pipe sections. The air compressor sits in the basement, alongside a water tank. You can barely hear the compressor running outside the house, as opposed to my loud 5KW generator needed to run my regular well pump.

My system is designed to just pump a few dozen gallons a day, and this is compatible with my smallish solar arrangement. However, with a larger solar capacity, a longer pump, and perhaps larger diameter water and air tubes, you could pump gallons per minute of water.