Application: Water Systems

Case 1: Using Precision Loggers to troubleshoot and fix a small-town water system

The system pulls water from a well that goes dry in late summer, so it has a large water reservoir that is always kept full. It also usually pumps from the well to directly fill a 22-meter (70 ft) water tower that supplies the town. The symptom was that occasionally the tower tank goes empty for no known reason, and the problem was getting worse over time.

For this troubleshooting task we used five Precision Process Signal loggers. Three of them measured on-off relay contacts controlling motorized valves, one measured pump motor temperature with a non-contact 4-20 mA temperature sensor, and one measured pump motor AC current using an AC current clamp. The graphs were made using Precision Loggers Software running on an iMac M1 computer. One of the graph lines was hidden because it was not required.

From the first graph you can see that when the pump relay is ON, the pump motor sometimes runs and sometimes doesn’t. We found that the pump motor failed intermittently. Replacing the motor solved the problem but revealed more trouble.

Now the pump motor runs continuously, overfilling the reservoir

The pump kept on trying to fill the reservoir at a time of year when the reservoir should have already been full. A short hike to the hidden reservoir showed that it was overflowing, and that the reservoir-full switch had failed in the open position. You can see this confirmed in the graph below, made after we had seen that the reservoir was completely full to overflowing.

Replacing the reservoir-full switch solved the second problem

The graph below shows that when the reservoir-full switch was replaced, the new pump was not trying to overfill the reservoir any more. Instead, the pump motor was off most of the time, switching on every 15 minutes to fill the water tower only.

The graph showed exactly what the problems were so that we could proceed with confidence.

Knowledge about the water system, gained by using Precision Loggers, helped to solve a long-term, gradually worsening water system problem that seemed unsolvable. The pump motor will now last much longer because it is running a 2 to 10% duty cycle, instead of 100%. The well water now lasts much longer into the dry season because it is not being pumped out needlessly. And the townspeople are happy to have a reliable water supply year-round.

Case 2: Water System Pipes Freezing in Winter

The small town’s water system pipes would sometimes freeze during a very cold winter, resulting in severe damage to pipes, valves and pumps.

For this troubleshooting task we used four Precision Temperature loggers. The loggers were very easy to place in various locations because there are no wires to run or sensors to connect. The graphs were made using Precision Loggers Software running on an iMac M1 computer.

From the first graph you can see that even though the electric forced air heating is running (blue line) at night the motorized valves (yellow line) and water pipes near the floor (red line) would be vulnerable to freezing if the outdoor temperature (orange line) went much colder than -4.55 degrees C.

Solution: The air duct from the heater was re-routed to deliver its warm air to the areas vulnerable to freezing, raising the temperature of the floor & wall water pipes, and the motorized valves. Now the pipes won’t freeze even if the outdoor temperature goes down to -25 degrees C, which is colder than it ever gets in this location. The graph shows us that the water pipes and motorized valves are 26 degrees warmer than the outdoor temperature.