This maybe a little out there but I'll ask anyway. We have been thinking about getting a geo-thermal system for our home and I stated thinking of better ways and wondered why A septic tank is never incorporated into the design other than the obvious answer. I know our family of four uses alot of hot water every day on average 4 showers,a load of dishes,laundry,washing hands. why cant all that hot water be used to help heat the loop instead of wasted down the drain? I know the tank will usually melt several inchs of snow in the winter time so it must be warm in there. Seems like I heard that the process of braking everything down in there also produces heat. I'm not saying it would eliminate the loop needed just help supplement it. Maybe a shorter loop or shorter run times for the geo-thermal unit. Is this something that has been thought/tried before or is there something I dont realize that would make this impossible? Seems like the tank could easily be insulated before or during an install to help hold in the heat.
Crazy Geo-Thermal Idea
- Thread starter afish
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Note to self; don't respond to leaking geo-thermal loop at afish's house.
I don't know, but would guess that there is some code about keeping those systems separate. But, if you were building a system from scratch, you could cirle the septic tank with a loop or three....
jb
I don't know, but would guess that there is some code about keeping those systems separate. But, if you were building a system from scratch, you could cirle the septic tank with a loop or three....
jb
Tig
Elite Member
I have heard of heat recovery from waste water but never from the actual septic tank. There cetainly is heat in the tank.
Brad_Blazer
Veteran Member
Sounds like a good idea. Put the septic loop after the ground loop to get the most out of warmest part and also to keep from overcooling the septic tank. You sure don't want it to freeze. In summer reverse the flow or bypass the septic loop if there is any foreseeable problem with heating up the septic tank.
woodlandfarms
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There is some sort of heat generated out of septic but I am not sure how much. Family of 4, lots of cold water coming in from flushes, septic tank underground. Cannot imagine it is very much. I guess I could put the wifes turkey thermometer in the system but.... We all know how that would end...
Kind of a side note, this guy in Austin is using his air conditioner to heat his pool.. Instead of a fan and a heat exchanger on the roof, he put it in his pool. Works like a charm, and thus he has one of the highest seer rated homes in the world...
A big side note. The "experts (people who desing high seer homes)" are now more concerned with cooling than heating, and that the US uses some astronomical amount of energy to cool compared to heat. Heating is much more energy efficient than current cooling methods. I put this out there because I never thought of energy this way, but in looking at the bills, it really makes sense. I spend way more in the summer than in the winter...
Kind of a side note, this guy in Austin is using his air conditioner to heat his pool.. Instead of a fan and a heat exchanger on the roof, he put it in his pool. Works like a charm, and thus he has one of the highest seer rated homes in the world...
A big side note. The "experts (people who desing high seer homes)" are now more concerned with cooling than heating, and that the US uses some astronomical amount of energy to cool compared to heat. Heating is much more energy efficient than current cooling methods. I put this out there because I never thought of energy this way, but in looking at the bills, it really makes sense. I spend way more in the summer than in the winter...
I'm sure there are all sorts of building codes concerning this, but when I was in HVAC we sold a product for waste heat recovery-- a double-wall vented heat exchanger that would capture waste heat from grey water (before entering septic system).
Had a customer who cobbled together a system using an old evaporator coil submerged in a 55-gallon drum into which waste water from sinks drained before leaving the building via the normal route.
Careful-- kitchen/dishwasher waste water often contains grease, which, when exposed to cold incoming water will congeal & plug things up-- better to stick with shower discharge, maybe....
You can also purchase a desuperheater coil to add on to an existing (central) AC system, which works well to pre-heat incoming cold water before going into the DHW heater, with the added benefit of keeping compressor head pressure down.
Had a customer who cobbled together a system using an old evaporator coil submerged in a 55-gallon drum into which waste water from sinks drained before leaving the building via the normal route.
Careful-- kitchen/dishwasher waste water often contains grease, which, when exposed to cold incoming water will congeal & plug things up-- better to stick with shower discharge, maybe....
You can also purchase a desuperheater coil to add on to an existing (central) AC system, which works well to pre-heat incoming cold water before going into the DHW heater, with the added benefit of keeping compressor head pressure down.
Bill Barrett
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Been thought of, been done. Against code, and screws up the anaerobic digestion so I've been told.
sunspot
Gold Member
I remember a guy in Orlando doing that 30+ years ago. He wanted his pool a bit warmer. It worked and as a side benefit, his electric bill went down a good bit.
AlanB
Elite Member
Could you do a "tank in tank" type system.
Inside tank would be your standard septic tank, outside tank would be oversised, like a dual wall petroleum tank.
Lay your pex or whatever heat transfer tubing in the outer tank and fill with some kind of magic heat transfer substance? Treated water maybe or some form of gel?
Inside tank would be your standard septic tank, outside tank would be oversised, like a dual wall petroleum tank.
Lay your pex or whatever heat transfer tubing in the outer tank and fill with some kind of magic heat transfer substance? Treated water maybe or some form of gel?
dirtworksequip
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AK, once you sucked all the heat out of the septic tank you would have one huge poopsicle and back up into the house.
Better yet..............why not layout a burried geo field and then cover it with 3 or 4 feet of mulch. As the mulch breaks down it will transfer some of it's heat to the ground. Which should help out with how it performs in the winter months.
Sincerely, Dirt
Better yet..............why not layout a burried geo field and then cover it with 3 or 4 feet of mulch. As the mulch breaks down it will transfer some of it's heat to the ground. Which should help out with how it performs in the winter months.
Sincerely, Dirt
Move to Wisconsin! I spend about 7-800 in propane for hot water, dryer, cooking and heat from September 30th to March 30th. (Wood heat) I have less than $50 in AC bill this year so far. Actually, much less as I only had to turn it on 5 or 6 days this summer.
The anaerobic digestion would be my main concern as well. As far as it being code to keep the systems separate I dont really see why, neither one is ment for human digestion. If the loop did get a leak what is the difference between it leaking in the ground or into a tank and then going out to the field. Either way I would not worry about that happening to much. I'm not sure what the life span of the pex is but I'm pretty sure it will outlast me. As far as the cold water that goes down the drain affecting it negatively the cold water that goes down the drain is the same water that they would use in a open loop system if not warmer from sitting in the storage tank (well water) and the plumbing lines in the basement. My basement is 2 degrees warmer in the winter than the rest of the house with the basement heating zone turned off.
Yes I've seen the grey water heat collector before. If memory serves correctly it was a piece that replaced a vertical section of the main stack pipe. If I'm correct it doesn't seem like it would work very well because the water would be rushing by so fast it wouldn't have time to extract the maximum amount of energy.
Obviously this would not work for everyone and end the energy crises. Someone living in southern calf. has different needs than me as far as heating and cooling goes. But I buy about 1000 (2.35 per gallon this year) gallons of propane a year for heating my home and water.
A separate tank in the basement to hold the gray water before being discharged might not be bad idea either. That way you dont have to worry about the poopsickle and the tank would be sitting in a nice cozy 70 degree basement. I just dont know if there would be enough water generated a day to make a big enough impact.
Yes I've seen the grey water heat collector before. If memory serves correctly it was a piece that replaced a vertical section of the main stack pipe. If I'm correct it doesn't seem like it would work very well because the water would be rushing by so fast it wouldn't have time to extract the maximum amount of energy.
Obviously this would not work for everyone and end the energy crises. Someone living in southern calf. has different needs than me as far as heating and cooling goes. But I buy about 1000 (2.35 per gallon this year) gallons of propane a year for heating my home and water.
A separate tank in the basement to hold the gray water before being discharged might not be bad idea either. That way you dont have to worry about the poopsickle and the tank would be sitting in a nice cozy 70 degree basement. I just dont know if there would be enough water generated a day to make a big enough impact.
Bill Barrett
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Here is a good site. Question was asked.
Enviro-Tech: Geothermal Technology Clean Energy Renewable Energy Systems
Enviro-Tech: Geothermal Technology Clean Energy Renewable Energy Systems
excelagator
Gold Member
I think the idea is useable. What if you ran line in the top end of the poop tank. This way you would claim the heat in the upper part of the tank? This would not "cool" the lower end of the tank. Maybe one has done this because either it has not been done or very dangerous.
If you are spending time in a live tank watch out for .... and Methane inhalation. Too much of it will kill you quick. I spent and hour (in and out) hanging upside in our septic unclogging a one of the pipes. It was not fun!
I remember a article on Farm Show where a guy ran 300 foot of drainage tile (flexible stuff) in the ground. He went down 8 feet. one end was hooked up to his high efficient gas furnace and the other end was his air intake. The drain tile preheated the air or colded it depending on the season. He took a reading over 2 or 3 years and saved about $300 a year. Now mine you this guy in Canada too!
If you are spending time in a live tank watch out for .... and Methane inhalation. Too much of it will kill you quick. I spent and hour (in and out) hanging upside in our septic unclogging a one of the pipes. It was not fun!
I remember a article on Farm Show where a guy ran 300 foot of drainage tile (flexible stuff) in the ground. He went down 8 feet. one end was hooked up to his high efficient gas furnace and the other end was his air intake. The drain tile preheated the air or colded it depending on the season. He took a reading over 2 or 3 years and saved about $300 a year. Now mine you this guy in Canada too!
charlz
Elite Member
I've read about people doing this for greenhouses. The biggest problem was condensation and the resulting mold etc. in the pipes.
excelagator
Gold Member
There are automotive AC duct coating treatments that will prevent mold. High efficiency furnace build up alot of condensation internally and at the exhaust side. so I am sure there is mold in mine!
excelagator
Gold Member
My father lost his class ring in a grass pile when I was kid. The pile was 2 feet man there was alot of heat in there!
I think you could used insulation board over the top and the side to retain the heat.
ampsucker
Platinum Member
man, you guys are stealing my ideas!
i was going to suggest looping the pex under a large compost pile. if you have a big yard with lots of leaves and grass clippings, free pre-heating in the winter. plus, you'll have a great garden the other months!
how about capturing the methane from the septic's anaerobic digestion and using that to fuel a small pre-heater?
another good source of heat are all the fridge and freezer compressors running all the time in every house. going to an externally mounted compressor and condensor for all the freezers and fridges (like super markets use) could also provide a good source of preheat. i think that would be more useful than the small amount of hot water.
our hot water fuel bill uses only about 9-13 therms during the summer months (only hot water is gas) compared to the 100-200 therms additional during winter to heat the house with the gas furnace. so 5-10% savings if you could somehow capture ALL the wasted heat. i think the payback on this would be way too long to make it worthwhile.
that's the problem with most of these projects. if everybody did them, it could save a lot of energy, but it's not cost effective for the individual.
amp
i was going to suggest looping the pex under a large compost pile. if you have a big yard with lots of leaves and grass clippings, free pre-heating in the winter. plus, you'll have a great garden the other months!
how about capturing the methane from the septic's anaerobic digestion and using that to fuel a small pre-heater?
another good source of heat are all the fridge and freezer compressors running all the time in every house. going to an externally mounted compressor and condensor for all the freezers and fridges (like super markets use) could also provide a good source of preheat. i think that would be more useful than the small amount of hot water.
our hot water fuel bill uses only about 9-13 therms during the summer months (only hot water is gas) compared to the 100-200 therms additional during winter to heat the house with the gas furnace. so 5-10% savings if you could somehow capture ALL the wasted heat. i think the payback on this would be way too long to make it worthwhile.
that's the problem with most of these projects. if everybody did them, it could save a lot of energy, but it's not cost effective for the individual.
amp
Matt_Jr
Platinum Member
How about raising geese and plucking their feathers and filling your attics with them.
Seriously-anyone heard of a stirling engine? Google "stirling engines". You could use several that are powered by the sun(engines mounted on the roof) to turn another to make cold air. Put one cylinder in the house the other cylinder outside. FREE HEAT AND A/C. To change the heat to a/c just spin the engine the opposite direction. Then a fan powered by yet another stirling engine can move air through the ducting, and a thermostat operates a flap that regulates the temperature in the house and voila-free heat and a/c. Stirling engines are cool.
. Seriously-anyone heard of a stirling engine? Google "stirling engines". You could use several that are powered by the sun(engines mounted on the roof) to turn another to make cold air. Put one cylinder in the house the other cylinder outside. FREE HEAT AND A/C. To change the heat to a/c just spin the engine the opposite direction. Then a fan powered by yet another stirling engine can move air through the ducting, and a thermostat operates a flap that regulates the temperature in the house and voila-free heat and a/c. Stirling engines are cool
.jdmar
Gold Member
Good link...I guess that answers the question although I am surprised the sytem could cool a septic that much. I have thought of putting a shallower loop (2-3 feet only) since I have muck soil which is extremely high in organic material. I have not seen it freeze more than an inch or two down--and then only in spots. I think the constant slow decompostion keeps it "warm." I understand that deep ground stays about 55 degrees in this area...but I wonder if muck soil is hotter. Maybe I should rig some sort of thermometer at 2-4-6 feet this winter and test out the theory. Muck is sort of like a huge compost pile with topsoil thrown in for good luck. Anyone have experience with this soil type?
Peter
Peter
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