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Concept Test
We
completed over 400 hours of Septic Heater testing in a controlled environment
during the fall of 2003. Twin
City Testing (TCT) installed temperature monitoring equipment including thermocouples, a
data logger, and a laptop computer to read and store data.
Testing Facility
We conducted the Septic Heater testing in a refrigerated semi-trailer that was divided
into three chambers. In one chamber we had a small lab that was kept warm and
contained all the sensitive computer monitoring equipment. In the second and largest
chamber we had 150 feet of sewer pipe strung out with temperature sensors at various
points within the pipe. This chamber represented "below ground" and was
kept at 15-20° F, the temperature of frozen ground. We also had a water reservoir
representing the septic tank in this chamber from which we could trickle water into the
pipes that would end up in a drop box. Water was collected in a stock tank and
pumped back up to the reservoir. The third chamber contained the Septic Heater
attached to an access pipe from the drop box in the second chamber. The third
chamber represented outside airtemp (intake air for the Septic Heater). We varied
the temperature of the third chamber from 35° F to -20° F.
What we measured
We monitored the temperatures of the pipes at 6', 30', 45', 90', 120', and 150' from the
drop box. We monitored the drop box water temperature (at the surface and below the
surface), the air intake temperature, heater output temperature, and ground temperature.
For ground temperature, we measured the air temperature at two different
points in the second chamber and used the average in our result charts.
Results
With -20° F intake air temperature the Septic Heater kept the
drop box and 110 feet of pipe from freezing. With temperatures above 0° F, the
Septic Heater consistently kept 150 feet of pipe above 32° F. The average length of
sewer pipe from the tank to the first drop-box (where the Septic Heater is typically
installed) is from 25 – 50 feet, so we are very pleased with the performance of the
Septic Heater.
With air temperatures below 0° F, the
Septic Heater runs continuously, maintaining a water temperature of about 40° in the drop
box. With air temperatures above 0° F, the Septic Heater runs for 2-3 hours,
heating the water in the drop box to 45° F, then shuts off. It takes the water in
the drop box about 3 hours to cool to 35° F, at which point the Septic Heater
re-activates. This on/off pattern continues
as long as the drop box water naturally remains at or below 35° F.
We tested with and without a trickle
of water running through the pipes. With a trickle of water, the drop box water took
longer to heat and cooled off more quickly. (The water entering the drop box was
cold after running through the cold pipes.)
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