Meltdown of an Above Ground Water Well Pump

What causes a pump meltdown in an above ground water pump? Lots of things. The most common is a stopped up Jet orifice. This will make the pump struggle to try and build pressure and when it cannot, it just runs and runs, and eventually it overheats the water, in a scenario where it turns to steam. Since most pumps are now utilizing plastic to make the impeller, the impeller can melt leaving the pump unusable.

Another symptom is a stuck pressure switch, or one that becomes out of adjustment. This will make the pump keep running and go into the steam producing mode as above.

So what causes the plastic to melt? Hot water? Yes and No.

Basically, when a pump, which is supposed to produce some level of vacuum, overheats, it falls under a different law of physics than water at atmospheric pressure. It will boil as low as 120 degrees. Boiled water creates steam. Steam will distort plastic very easily. It is no wonder steam is used to cook many foods!

I once had an engineer declare that a motor on a particular brand pump had a thermal overload that should have kicked out, and therefore we should warranty the pump, that had been installed on an older well. It was a seemingly good argument, except for one fact that he missed. That thermal overload would only activate at 150 degrees F above ambient temperature, and since it was 80 degrees F out, that would be 230 degrees. The pump as tested was only 130 degrees on the pump end (using a hand held device). We explained Boyle’s law to him, which must be somewhat embarrassing for an engineer to have to hear, but he agreed with our diagnosis at that point. Here is a demonstration of water boiling at lower temps under vacuum.

We have sensor devices available which will shut down a pump if needed. They are expensive, but they work. I cannot tell you how many times those sensors will save the customer big money for a problematic pump system.

Risky situations to install jet pumps would include any well with iron or sulfur contamination (which is a good many), and pumps that pump from ponds, also any pump with a remote location away from water source, and when a “plastic” check valve or foot valve is used! Try to eliminate issues up front by using a contractor who knows how to prevent these issues, and understands how to install these sensors to automatically shut down the pump.

Thanks

Jody Anderson