Frequently Asked Questions - Water Pumping

Q.  What are the basic types of water pumps?

A.  Submersible, for deep wells and surface pumps for shallow pumping.

Q. Are solar pumps more expensive than conventional AC choices?

A. Solar pumps are perceived to be expensive, because their initial cost is high. If your water sources are remote from power lines, add up your long-term costs of feeding and fixing generators, repairing windmills, etc., including time and transportation to well sites. Now consider the savings with a solar pump that only needs attention every 5 to 10 years.

Q.  What are the limits of a surface pump?

A.  As a general rule, a surface pump can draw water up only 20 feet; otherwise, the water begins to vaporize adding air bubbles to the water flow.  If you will be pumping at an elevation higher than 1000 feet above sea level, then subtract 1 foot for every 1000 feet of elevation.

Q.  What are the advantages of a submersible pump?

A.  There is a greater degree of design freedom.  The submersible pumps fits in a 4 or 6 inch well casing as far down as you need it to be.

Q.  What are the different pump mechanisms?

A.  Surface pumps are often centrifugal pumps.  The motor spins an impeller which pulls water in and forces it out with a centrifugal force.  The water in captured in the front housing and sent out the pipe fitting of the outlet.

     Submersible pumps are piston pumps.  The piston goes in and out of the cylinder pushing and pulling water in both directions.  The water comes from the pump in pulses.  These pumps work with positive displacement.  The water is trapped and forced by a sealed cavity against pressure.  Even when moving slowly in cloudy weather, the pump will still force water uphill.  A centrifugal pump needs to move at least 6 gallons per minute to move water uphill. 

Q.  How do I know what size pump to purchase?

A.  First, determine your usage.  Estimate about 25 gallon per day (gpd) per person, 15 gpd per tree and 25 gpd per head of cattle.  Then divide the gpd by the hours of peak sun available at your site.  [We can help you find a sun map for your area.]  This will give you your gallon per hour.  Divide that by 60 to determine your gallons per minute (gpm).

     1500 gpd         =     230 gall/hr   =  3.8 gallons per minute

6.5 peak sun hrs          60 minutes                                       

     Second, determine your maximum lift.  Measure the vertical lift from the level of the well top to your storage tank.  Add the distance from the ground level down to the water level.  Keep in mind that the draw down water level may be lower then the static level.  For example, water may sit at 20 feet below the surface, but if the water enters at 70 feet below the surface, you probably want your pump to sit at 80 feet below the surface.  So, the max lift would be 80 feet plus the vertical distance to the tank.

Once you have your gallons per minute and maximum lift, use the manufacturer's specification sheet to determine the correct pump model for your application.  We have the manufacturer's specs on all of our pumps and will be getting these on the website soon.  In the meantime, give us a call or send an email and we will do the research for you.

Q.  How do I choose the correct solar panels for the water pump?

A.  First, look on the manufacturer's specifications for the particular pump and find the wattage.  Let's take 250W as an example.  You will need 20% more then the pump requirement because the solar panels will produce less then their power rating with aging, dust accumulation, etc.  So, for a 250W pump, you will need 300W from your panels (250 x .70).  You could use four 75W panels (4 x 75 = 300) or two 150W panels.

Q.  How large should my water tank be?

A.  You should plan for at least 5 days of water supply.

Q.  What if I am using more water then I estimated when I purchased the solar panels and the pump?

A.  You can provide substantially more energy by using a solar tracker.  During the summer, this will give you *%.  This will increase your peak sun hours from 6.5 to 9, for example.

Q.  Can I get more water if I use batteries?

A.  Yes, but remember that if the batteries pump water all night, the solar panels will need to recharge the batteries the next day along with pumping water.  So, you will need larger solar panels.  Considering the additional solar panels and the cost of batteries which need to be replaced every 5 or 10 years, it is usually more economical to store the water in a tank.

Q.  What should I have the well driller do before I install the pump?

A.  He or she will put in the casing so the ground doesn't fall in.  The well cap should have a rubber sealed and an opening for the electrical along with a conduit and a junction box on the side of the casing.

Q.  What if freezing is a problem?

A.  The water pipe coming out of the well casing should be underground about 5 feet.  The well driller will install a pitless adapter (a sliding fitting) where the pipe comes in to the casing and attach it to thee pipe.  The pipe will then go out underground to your storage tank.  The hole in the casing is sealed with a rubber gasket.  Inside the casing, you will slide the pitless adapter down into a dovetail joint making a water tight connection.  See question below regarding installation.

Q.  What are the supplies I will need to install the pump?

A.  Submersible cable the length of the vertical drop down the well to where the pump will be plus a bit extra.  Drop pipe made out of polyethylene about the same length as the submersible cable.  A safety rope to hold the pump in case a connection breaks (don't skip this step).  A splice kit to connect the pump leader cable to the submersible cable along with some shrink tubing to make the splices waterproof.

Q.  How do I install the water pump?

A.  Cut the cable and the water pipe to the number of feet down the pump will go.  Connect the water pipe to the pump.  Use teflon tape for connections.  Tie the safety rope to the pump.  [See the Ashley Book of Knots for help with knot tying.]  Connect cable to pump using splice kit and make sure you sell each splice with the shrinking plastic tube--heat the tube with a cigarette light to shrink.  Make a slack loop in the cable so that if the pump does drop, it will not dislodge the electrical connections.  Use electrical tape to tape up the loop.  Then use cable ties to tie together the cable, water pipe and safety rope at about every 10 feet.  Remember to allow some slack in the cable at every cable tie point because the cable will not stretch but the rope and the water pipe will.  Attach the top of the water pipe to the pitless adaptor.  Attach the top of the pitless adaptor to a PVC threaded pipe (this is used just for installation). 

     Drop the pump slowly down the well.  This will get very heavy, so have one or two people to help you.  Don't take chances!!  Once the pump is down and you are holding on the PVC pipe that is attached to the pitless adaptor (you may want to put a little grease on the O ring of the adaptor to help it slide in) have one or more persons hold on to the safety rope (not the cable) while you maneuver the pitless adaptor into place with the PVC pipe.  Once it is in place, unscrew the PVC pipe and remove.  Keep this pipe for later use in removing the pump for maintenance.

     Tie the safety rope to a Ubolt in the casing.  Take the cable from the casing and thread it through the conduit and into the junction box.  Connect it to the wires gong to the solar array.

Q.   What size wire do I need?

A.   The higher the voltage, the smaller the wire.

Q. How do I wire the solar panels?

A.  There is usually a wiring diagram that comes with the panel.  It is fairly easy and can be performed by someone with basic electrical knowledge.  It is a good idea to have a multimeter to check each connection.

Q.   Do I need a controller?

A.   A controller allows you to turn off the solar array to the pump for maintenance without disconnecting the wires.  Different controllers will give you different options as far as function and displays.

Q.  How do I get pressure if I cannot locate my water tank on a hill?

A.   Use a booster pump and a tank.  This will give you pressure that is approximately equal to a 100 foot high hill.  Use a pressure switch so that when the pressure drops below a set point, the pump automatically comes on and pressurizes the tank.

Q.  How do I maintain the water pump?

A.   If the pump has brushes, which are blocks of carbon graphite compound that conduct electricity to the moving part of the pump, you need to replace these every 3 to 10 years.  It is very simple with centrifugal pumps and only a bit more complicated on submersible because you need to take the casing apart to get to the brushes.  If the pump has a diaphragm, you will need to replace that every 2 to 4 years.

     A brushless motor is more expensive and although you do not replace the brushes, it has a more complex set of electronics that fail in different ways and more randomly.

Q. When I know the total pressure, how can I translate this into vertical lift?

A. The basic formula is 2.31 psi = vertical feet. Since you know the head, just divide by 2.31 for a psi (pounds per square inch) figure. In reverse, if you already have a water pipe installed, you can use a pressure gauge at the bottom to find your head - just multiply the psi reading times 2.31 to get vertical feet.

For all of our pumps and accessories, click on this link: Water Pumping.  Call or email with questions.  March 1, 2008

Short glossary of water pumping terms