Using a Dankoff Solar Powered Water Pump – Part 5, by Tunnel Rabbit

(Continued from Part 4. This concludes the article.)

Spare Electric Motor

The motors used in the Dankoff slow pumps are of the highest quality and would not need service except for brushes. However, it would be nice to have a spare motor just in case an armature fails, or a bearing fails, or if the original motor is lost to theft. If the spare pump motor was stored in an alternate location with a spare pump head and coupler, then we could eventually fabricate the missing parts.  A recent quote from the owner, Kenny at Dankoff Solar Pumps: $539 for the motor, and $22 for the motor coupler that has uses a rubber piece that could dry up and crack after 20 years of service.

To make a complete spare Dankoff Slow Pump from the parts mentioned in this article, we would have to manufacture the brackets and fasteners (bolts) to save ourselves roughly $400 off the MSRP. That is currently $999 for the complete pump, but the process requires certain fabrication skills, and a few common tools.  In the event that the motor fails, it would likely need only a bearing that could be found at an auto parts store, that may or may not be in business, or available, in the grim near future. Given that we have a complete spare motor, one set of three replacement brushes would not be needed, lowering the overall cost of long-term operation. As a rule, armatures rarely fail, and the commutators will last 15 to 20 years, but even given the slow speeds of these motors, it is possible that a bearing could go bad. To avoid the cost of a complete spare motor, buy replacement bearings.

Spare Manifold and Intake Assemblies

Leaks in the intake can occur, so be prepared to repair the lines. Have several backup filter housings accompanied by spare intake lines, along with fittings and the requisite adhesives.  I prefer complete assemblies that can quickly be swapped in, thereby reducing the risk of losing a key fitting, or part. Having several manifolds as completed assemblies for the outlet side of the pump is also a good idea. I have one of each in Pex, copper, and PVC as I happen to scrounge the material. Pex is best, but difficult to repair in the field without an expensive crimping tool.  PVC requires glue that has a limited shelf life, and PVC cracks easily when frozen. Copper pipes crack when frozen hard. Copper plumbing requires high heat, but solder and flux do not degrade over time. Under no circumstances should galvanized pipe or iron pipe be used anywhere in the plumbing as it eventually rusts, and the rust could find its way into the all-brass pump head and do permanent damage. Stainless steel and brass pipe and fittings would be ideal, but their cost is high. Pex pipe with brass fittings will survive a freeze better than any of the other options. The pump head itself will take a light freeze, but it should be completely drained before winter storage.

Minus the pressure switch in the photo, this is an example of a brass outlet manifold that can be used. My manifold has four valves to send water to different sections to be irrigated, and to a neighbor located 2,000 feet away.

Intake Line and Foot Valves

As both an intake and outlet line, a 3-5 foot length of 1/2-inch Pex line serves well as strain reliefs on the pump, when attached between the pump and the outlet manifold, and between the pump and the filter. The suction side of the pump can draw 20 feet of water when at sea level. As a rule of thumb, subtract 1 foot of suction line for every 1,000-foot increase in elevation. At most higher elevations, it will draw at least 10 feet. It is wise to keep the suction lift to a minimum, and use a larger-diameter intake line, rather than just 1/2 inch. A 1-inch suction line would not be excessive.

When taking water from a surface source, the length of the intake line could be considerably longer if the height above the water source is lower rather than near the maximum limit, but priming the line more often, prior to start-up operation might be necessary if there is a slow leak in the foot valve. In morning low-light conditions, the pump can run very slowly if managed by a pump controller. It could reduce the amount of water pumped each day if there was a slow leak at the foot valve, and the pump had to fill the intake line and filter, running dry for a period of time each day. This situation should be prevented, since we do not want the pump turning when there is no water in the pump.  The water is its lubricant.  In a societal collapse environment, close daily inspection and monitoring of our equipment is strongly advised.

Using 3/4″ Pex line from the filter housing to a short section of rigid line, i.e. PVC or copper pipe, to a 90-degree elbow downward to the foot valve, allows the foot valve to be placed inside and at the bottom of a 6-gallon bucket with holes drilled into sides several inches off the bottom.  The line is secured and centered in the bucket as it run through the center of the lid that snaps in place. The bucket could be filled with clean small rocks. This small rock not only acts as ballast to anchor the intake line in a flowing water source, but also stabilizes and protects the foot valve from debris at the bottom, and the small rocks act as a coarse filter.

A foot valve is not absolutely necessary if the line will be primed before running the pump each day, but it is excellent insurance that the pump would not risk running dry at startup. Keeping a spare 3/4-inch foot valve is a good choice. Check valves are not spring-loaded, and are not an equivalent, but could be helpful if a foot valve is not available. When using a check valve as a last resort, or as a substitute for a foot valve, prime the intake line in the morning before the beginning operation for the day.  PVC check valves do use a rubber gasket and might seal better than all brass check valves. The best substitute is a check valve designed for deep wells.  These are spring-loaded and use a rubber gasket, and are typically 1 inch in diameter. A reducer from 3/4″ to 1″ with a 3″ inch in length close nipple would be needed to attach to a 3/4″ intake line.

Redundant Filtration

Spare filter housings are a necessity as well. Inexpensive whole house filter housings can be purchased in multiples of 5 each, and at a discount. Use plastic fittings to thread into these whole house filters as metal fittings are made to different specifications and tolerances, and the hard metal can easily cross thread and damage the soft plastic threads that are in these filter housings.  More expensive whole house filters offer threaded metal inserts to avoid this hazard.

Even though the water quality may appear to be excellent, a 10-micron string filter element could become partly clogged and restrictive sooner rather than later.  To avoid wear on the pump from cavitation, it is better to change these filters often. Listen for a buzzing noise as an indicator that the intake line is somehow restricted, or has a leak.  My stock of 40 spare filters will hopefully last up to 20 years. Even if the consumption is rate is twice that of the anticipated replacement rate, there would be a 10 year supply. Do not even think about running this pump without a filter. A 5-micron filter, recommended by some vendors is too restrictive, according to a Dankoff technician that I spoke with.  If all I had access to were 5 – filters, then I would use two of these filters side by side to feed a single intake line into the pump.  A coarse filter element that would be a 20-micron filter, ahead of 10-micron filter, may extend the life of the -micron or 5-micron filter.

Additional Operational Considerations

In the event of a societal collapse, the slow pump would be an irreplaceable and essential asset, Therefore it would not be operated automatically, but manually switched on each day, and good operation verified at the start of the day. It could be that the intake line was damaged, or dislodged overnight by an animal, and as a result, the pump ran dry, and became ruined. The use of clear plastic in the filter housings, or at a check valve installed after the priming port, does help diagnose problems. Verification of good operation can also be made with the use of the pressure gauge located at the outlet manifold.

System Integrity and Security

Walking the lines looking for leaks and verifying output daily, ensures that the system is healthy.  The use of quick-connect couplings allows for the quick and convenient nightly removal of the pump should there be the threat of theft. Mine will be protected during daylight hours by a home-built MURS Dakota Alert sensor without an IR sensor, but instead on a tripwire to a small pump housing.  One can purchase the transmitter separately for half the cost of the complete unit. The use of a tripwire ensures that fewer false alarms occur by wildlife visiting the water source, and that the pump and Dakota Alert Sensor can be protected from the elements by a waterproof housing.

If an intruder removes the secured housing, an alert is sent to a handheld transceiver. Ideally, the housing should be made to be as indestructable as possible, yet determined thieves could defeat just about anything I could afford to make for the occasion.  After all, they would be very motivated, as they would discover that without water, nothing grows abundantly enough to feed families. It may be necessary to post a guard on it 24/7 if it is needed to produce water during the night. Be prepared to replace the plastic couplers, or use brass couplers that wear longer, to quickly disconnect the pump and secure it for the night.


If you are in the woods for good, this could be a very useful pump. The pump is portable, even packable with foldable PV panels, and can be moved to a neighboring property where a cistern can be filled. Or it can pump 250 feet (#1303) to 400 feet in elevation (#1308, pump controller required), or conceivably even several miles on more level ground to a neighbor, or remote patch of good soil. For my situation, I chose these two different pump heads to be used in different applications, increasing the options and versatility.

A slow pump is also ideal for a community garden. And a gravity-fed system can be primed by pushing piped water over a hill from a source higher in elevation. It can also be run off the battery bank of a PV system, 24/7, producing several thousand gallons every 24 hours, irrigating enough acreage feed 10 to 20 families. That would be a sizable community garden. Solar water pumps and ram pumps of many kinds will be invaluable as they will be necessary for irrigation in most situations.  I’m glad that I bought mine in 2008, and have had over a decade to get to know it thoroughly. To wit, some of the important information provided here, is not found anywhere else in print.

Even if this is not the best pump on the market for the purpose and money, this kind of hard to get information is the technical support needed to keep it running, when other pumps will not be, because of a lack of technical support. This is the same reason why wise farmers are getting away from shiny new tractors, and are driving up the price of vintage tractors, because these can be serviced by any farmhand.  And so can these pumps.

If you are interested in obtaining the pump discussed, although the prices and links are several years old, the items needed are provided in these articles:

My Solar-Powered Dankoff Slow Pump System – Part 1, by Tunnel Rabbit

My Solar-Powered Dankoff Slow Pump System – Part 2, by Tunnel Rabbit

Recommended Vendors

Kenny at Dankoff Solar Pumps.

Thad at is extremely knowledgeable and has helped me understand this pump.  At the Humboldt web site, see the page: Dankoff Solar Water Pumps for your Homestead or Ranch.

For supplemental information to this article, review all the available literature available at, and others.

Disclaimer:  I am in no way associated with any of the named companies and do not benefit financially or tangibly from mentioning them. I’m just a happy customer.