Thread: 103 Degree Water in Sump Pit

I looked at a house yesterday for a buddy who is buying. The basement has an aftermarket water control system installed (trough and sump pit with pump exhausting to exterior). Since the pit cover was bolted in place, I only had a silver-dollar size hole to look through. When I looked in the hole, warm steam came out. I shined my light in to see the pump and float switch completely submerged by about 3-4 inches and water circulating in the pit. My laser thermometer registered a temp of 103 degrees for the water in the pit. It was 17 degrees outside and I was scratching my head. After looking again at the exterior discharge line for the pit, there was no water or ice around the end of the pipe and it appeared free of obstructions. My final conclusion is that something in the discharge line like the check valve is defective or blocked, the pump has been running non-stop because the float switch is up, and the heat generated by the pump heated the water. No other lines could be seen entering the pit that could possibly make the water that warm.

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I would say the friction of the water circulating around the pump caused the heat (in combination to the heat from the motor). The float is stuck and there is simply nothing to pump out. I would not suspect a plugged discharge unless the pit was full. Pumps can only pump out to a certain level, as little as 1/2" depth for some, much more for others. When there isn't enough depth for the pump to prime, it will cavitate. Cavitation and the friction of the water molecules creates heat. If water were coming into the pit, the water would be much cooler, probably around 50-55 degrees.

BTW, I would recommend replacement of the pump as they are not designed to run continuously for long periods of time.

What Jon wrote or the pipe has disconnected at pump and pump is recirculating water in pit never shutting off. If the water looks like it's boiling (you wrote circulating), the disconnected pipe from pump is the likely cause. I've seen both situations before.

Originally Posted by Jon Randolph

I would say the friction of the water circulating around the pump caused the heat (in combination to the heat from the motor). The float is stuck and there is simply nothing to pump out. I would not suspect a plugged discharge unless the pit was full. Pumps can only pump out to a certain level, as little as 1/2" depth for some, much more for others. When there isn't enough depth for the pump to prime, it will cavitate. Cavitation and the friction of the water molecules creates heat. If water were coming into the pit, the water would be much cooler, probably around 50-55 degrees.

BTW, I would recommend replacement of the pump as they are not designed to run continuously for long periods of time.

Now, I'm not a molecular scientist but I would think that in order for the friction of water molecules needed to warm cold water to 103f you would need something on the scale of a hydroelectric plant to generate that amount of heat.

Just about every sump pump I have seen are sealed pumps(oil filled) that are cooled by the surrounding water that they are submerged in. The pump case transfers the heat to the water. Logic would say that if the pump is running continuously without the addition of a good amount of cool water, and it is not discharging then the water in the sump would become warm after awhile, just like you are finding.

I'm with Scott on this one. Friction of the water or cavitation as a significant source of heat -- not likely. Submerged pump running continuously in water that is recirculating and that is not being pumped out and replaced by cooler water as a significant source of heat -- very likely.

Most people who have deep wells with submersible pumps know it's not a good idea to let the pump continue to run if the well runs dry; it will burn out the motor. Many have thermal limit switches to protect them for this reason.

Originally Posted by Brandon Chew

Friction of the water or cavitation as a significant source of heat -- not likely.

As an operator in a chemical plant, in the middle of winter in Indiana, I have seen centrifugal pumps that have been dead headed and running for as little as 1/2 hour cavitate due to the fluid boiling from circulating and not moving. These pumps are attached to the motor via a coupling so heat transfer from the motor is not likely. If ran for a very long time, the pumps would be so hot that you couldn't touch them and the pain would discolor.

Friction between molecules will cause the fluid to heat up.

Originally Posted by Jon Randolph

As an operator in a chemical plant, in the middle of winter in Indiana, I have seen centrifugal pumps that have been dead headed and running for as little as 1/2 hour cavitate due to the fluid boiling from circulating and not moving. These pumps are attached to the motor via a coupling so heat transfer from the motor is not likely. If ran for a very long time, the pumps would be so hot that you couldn't touch them and the pain would discolor.

Friction between molecules will cause the fluid to heat up.

Nobody is arguing that point.

A food processor will heat the food up in the chopping chamber and pre-cook it if you overprocess. One of the first things that is taught in culinary arts school.

Originally Posted by Jon Randolph

As an operator in a chemical plant, in the middle of winter in Indiana, I have seen centrifugal pumps that have been dead headed and running for as little as 1/2 hour cavitate due to the fluid boiling from circulating and not moving. These pumps are attached to the motor via a coupling so heat transfer from the motor is not likely. If ran for a very long time, the pumps would be so hot that you couldn't touch them and the pain would discolor.

Friction between molecules will cause the fluid to heat up.

If run longer you will be able to evaluate the effectiveness of the Shear Coupling generally installed between the Centrifugal Pump and Motor or Steam Turbine..........

Friction will get it hot. I've seen dead headed shallow well pumps that have melted the ABS suction line. The water gets super heated since it's under pressure and when the line fails it's quite loud.

Jon and Chad,

I didn't doubt that friction would be a source of heat, only that it would be significant compared to the heat generated by the motor. Based on your input it seems it can be a larger factor than I thought. Thanks for the education.

Brandon

It is also possible that the pump has become 'air locked'. The pump would be running but because of the air lock it could not get the water into the line.

I totally missed that the pump and float were completely submerged by 3-4 inches of water and read it as if there were 3-4 inches of water in the pit and it was circulating.


Yes, the motor will create enough heat for the water to heat up. As far as it being air locked, I doubt it. With that much water above it, the pump would re-prime itself and begin pumping again. I would suspect a blockage ir damaged impeller on the pump itself.

Speaking from past experience, my opinion is the discharge line is frozen and not allowing any water discharge. I have found that with out a proper bypass point in the line the pump will burn out. This is a real common issue in northren climates.