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Nice article in last issue about Geothermal Heat/Cool systems.
I’d like to know if you can put the ground heat exchange coils into the septic leach field.
It will always be wet, so the thermal conductivity will be high. Trenches are 3 to 4ft wide usually. Usually fill with crushed stone-probably need to put tubing in sand or fine gravel.
Has anybody tried this or can anyone forsee problems?
When the air is 105F, the thought of getting 60F temps to cool is VERY tempting.
If you already need to excavate for septic, this could make the systems much more reasonable in rural areas.
TIA,
Adam
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Adam,
As I understand it, the answer is no.
We have a Hydrotemp http://www.hydro-temp.com system with in-ground loops. A total of 750 feet of six foot deep trenchs holding 2,000 feet of loop. We paid about a dollar a foot for the digging. Our septic field has 580 feet of laterals and about 100 feet of line all about two feet deep. I don't know what the cost of digging these trenches were but they were gug in an afternoon. At the going hourly rate for back hoe work here that would have been about $200 worth of time. At first glance, I would agree that we could have saved some by combining the trenches but not much.
This is why it will not work. A septic system, by code, must be placed in undisturbed soil. There are systems that can be placed in fill but the engineering and material cost would exceed the relatively minor savings from combining the trenches.
We compacted our loop trenches as they were being back filled. Six months later, they had "sunk" an additional six to twelve inches. There is no way a septic system could settle that much and still work as designed. And, of course, the water in the septic system would facilitate settling which is why septic systems should not be placed in or over fill.
We are getting very good performance from our system. We keep our 2,300 sq ft house in the 78 to 80 degree range and our total electric bill for June (house, shop, and pool) was less than $100.
Steve
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Nice article in last issue about Geothermal Heat/Cool systems.
I'd like to know if you can put the ground heat exchange coils into the septic leach field.
It will always be wet, so the thermal conductivity will be high. Trenches are 3 to 4ft wide usually. Usually fill with crushed stone-probably need to put tubing in sand or fine gravel.
Has anybody tried this or can anyone forsee problems?
When the air is 105F, the thought of getting 60F temps to cool is VERY tempting.
If you already need to excavate for septic, this could make the systems much more reasonable in rural areas.
TIA,
Adam