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What kills bore pumps?

I receive many calls each week from people who have bought a pump from another shop or the pump was already in the bore on the property when they purchased the property, the pump has failed and they want to know why.   There are quite a few factors that effect the operation of a bore pump, they include the following:

Water Quality:   Water quality has an effect on every bore pump, sometimes the effects are very minimal and sometimes the effects are catastrophic.   Water that has a high or low range pH will kill a pump and motor, water with a high Chloride level will often kill the motor, water with a high iron oxide content can block the pump impellers or the water inlet and again, kill the pump and motor.   Damage caused by water quality is not covered under any manufacturers warranty.

Water Temperature:   Water at more than 30 degrees C will reduce the motor cooling effect and this can cook the motor if a shroud has not been fitted.   Water above 40 degrees C will definitely require a specially selected pump and motor or it will just die of overheating.   Water at 1 degree to say 15 degrees is perfect for pumps and motors and they will usually run for years and years.   Damage caused by water temperature is not covered under any manufacturers warranty.

Cavitation:   Cavitation is caused when the pump is allowed to operate without any back-pressure or load on it, this will always result in actual physical damage or even breakage of the impellers and other internal components.  It is very easy to eliminate any chance of cavitation with a Maric flow control valve fitted to the outlet on the pump.   You should never accept a manual gate valve as a form of cavitation prevention.   Damage caused by cavitation is not covered under any manufacturers warranty.

Upthrust:   Upthrust occurs at the moment when the pump starts, the motor is fed with electricity and the motor goes from zero revs to 2,850 RPM in a second and that tries to push the shaft up through the top of the pump, particularly if the pump is not fitted with a Maric flow control valve.   The result of upthrust will be a smashed top bearing also called a thrust bearing and possibly other broken internal components.   Damage caused by upthrust is not covered under any manufacturers warranty.

Running out of water:   If you allow the pump to "run-dry" then it will overheat and fail.   Operating the submersible bore pump so that it never draws the water level down below 1m above the top of the bore pump is critical.   It is easy to measure the water level in any bore and this should be carried out frequently enough so that you are sure that you know exactly where the water level is in the bore at all times.   This is particularly critical if you only have a single bore.   Damage caused by running dry is not covered under any manufacturers warranty.

DC Electrical Attack:   Sometimes stray DC current from a nearby electric train, electric transformers, electric fences or any other large machine that can produce DC voltage can leak through the earth and cause corrosion in the submersed bore pump motor.   These items that cause the DC can be up to 5 klms away from the pump.   Not all pumps are affected by this as firstly you need to have a source of DC current and then you need the necessary soil and water conditions to create the perfect storm for corrosion to occur.   Removing the DC source and installing sacrificial annodes can reduce damage but you wont even know that you have the conditions until you have killed the first motor.   Damage caused by stray DC voltage is not covered under any manufacturers warranty.

Lightning:   Lightning strikes often send millions of volts into the ground, your pump and motor are in water in the ground, make sure that you include your bore pump equipment on your insurance policy.   Damage caused by lightning is not covered under any manufacturers warranty.

Mud & Sand:   Bore pumps are designed to pump water not mud or sand.   50 grams of sand per 1,000 litres of water is the maximum quantity that is allowable, and 50 grams of sand is not very much, about a desert spoon.   If you have sand in the water it will act as sandpaper and erode the internals of the pump causing pump failure.   Mud is often worse, it will block the pump inlets, block the impellers and cause a reduced flow and pressure and eventually you will end up with a locked pump or a broken shaft.   Damage caused by mud & sand is not covered under any manufacturers warranty.

Excessive starts:   Most submersible bore pumps are restricted to 300 starts per day, I personally try and make sure that they don't need to start more than 12 times a day.   Excessive pump starts result in excessive electricity usage and that becomes expensive.   Excessive pumps starts often occur on stock watering systems where the troughs are fed directly by the pump, 200 head of cattle can cause the pump to start 500 times or more per day if the system is badly designed.   Excessive starts generally result in worn spline connections and broken shafts.   Damage caused by excessive starts is not covered under any manufacturers warranty.