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This was done in Vancouver for the Olympics. Also been done in Scandinavia for district heating systems.

Septic tanks are a "no" as they keep them selves warm, to keep the digestion process going. Cool it down, you stop it. You would soon end up with a tank full of shyte
Grey water does work, in a settling tank, but you do need to do the maths to ensure a correct energy balance. (better with large families, lots of general water use)
It is common to run part of the loop along a sewer pipe to pick up a little benefit.

OK.....everyone on your street...take a turn with flushing your toilet....lol

I have never tried this but would be interested in how it turns out. I think you could make one pass through the septic tank and not have a problem with freezing but not putting the whole loop in there. Otherwise in January it would be one frozen block creating other problems.

Originally Posted by grizzzlle

Please calm down glennac. Yes the OP (me) has thought about some of those issues. First you must know my backroud. Working with and designing those hydraulically engineered sewer lines is how I make a living. To say something that is occupying space in a line would deminish capacity is a blanket statement and is false. It is not unusual for a 21" pipe to only have a couple inches of flow in them for most of the year. During heavy rains yes flow might increase to half or more flow in the pipe. It is something that would have to be evaluated when looking at a line.

As far as not being allowed to tap into a system I have already asked about the idea and some interest has been shown. I need to get more information but am busy doing something else at the moment.

Pandoras box was opened years ago. Currently there are agencies that do rent (for a lack of a better way to describe it) there sewer infrastructure out to other utilities as a way of not having to dig up streets.

I am also not to conceded at the moment with how to install something in the sewer pipe. That would be a discussion farther down the road when trying to figure out different methods for the transfer of heat. Currently you would be surprised what gets shoved into a system on daily basis. There is an entire industry centered around it.

Interesting, yeah I knew about the low flow (most of the time) in a sewer system especially like in Atlanta where they have a combined storm and sanitary system which I understand are not allowed anymore. Just wanted to know if you had thought about those issues before posting here and just whistling Dixie.

If one really wanted to get serious about saving energy you would have nuclear power plants built downtown and use the waste heat to generate steam for heat in the winter and run absorption chillers in the summer and sell it to the downtown buildings but that is so so non PC that the wackos would be screaming theri lungs out. Good luck with your efforts there. Thank you very much

Please calm down glennac. Yes the OP (me) has thought about some of those issues. First you must know my backroud. Working with and designing those hydraulically engineered sewer lines is how I make a living. To say something that is occupying space in a line would deminish capacity is a blanket statement and is false. It is not unusual for a 21" pipe to only have a couple inches of flow in them for most of the year. During heavy rains yes flow might increase to half or more flow in the pipe. It is something that would have to be evaluated when looking at a line.

As far as not being allowed to tap into a system I have already asked about the idea and some interest has been shown. I need to get more information but am busy doing something else at the moment.

Pandoras box was opened years ago. Currently there are agencies that do rent (for a lack of a better way to describe it) there sewer infrastructure out to other utilities as a way of not having to dig up streets.

I am also not to conceded at the moment with how to install something in the sewer pipe. That would be a discussion farther down the road when trying to figure out different methods for the transfer of heat. Currently you would be surprised what gets shoved into a system on daily basis. There is an entire industry centered around it.

Originally Posted by whatsthat

I wasn't involved in the project, but the geo lines were fabricated into the concrete sewer pipes. It's not impacting the flow... at least as long as it's not freezing the water. I too hope the engineers involved thought of all of that.

If you google "sudbury geothemal sewer lines" the second link down gives some info on the project.

Understood. My post was really directed at the OP. Thanks for the reply.

Originally Posted by glennac

How in the world would you get your "heat exchanger" into a main sewer line? I'm sure if you asked permission to "tap" into it with your lnes they would say no but hell no.

You would be occupying space in their "hydraulically engineered sewer pipe and thus reduce it's capacity. Plus they would be opening Pandora's box for all kind of folks wanting special favors for this or that. I'm curious if you actually thought any about those issues. Thank you very much

I wasn't involved in the project, but the geo lines were fabricated into the concrete sewer pipes. It's not impacting the flow... at least as long as it's not freezing the water. I too hope the engineers involved thought of all of that.

If you google "sudbury geothemal sewer lines" the second link down gives some info on the project.

How in the world would you get your "heat exchanger" into a main sewer line? I'm sure if you asked permission to "tap" into it with your lnes they would say no but hell no.

You would be occupying space in their "hydraulically engineered sewer pipe and thus reduce it's capacity. Plus they would be opening Pandora's box for all kind of folks wanting special favors for this or that. I'm curious if you actually thought any about those issues. Thank you very much

Originally Posted by mahlv

i seem to remember either reading or hearing about planned geothermal communities doing this very thing with a specially developed 'coaxial' sewer pipe. It may have even been overseas, but it would be very interesting to see it work. I wouldnt do the septic thing as freezing your tank, inlet, outlet, or leach field would really be $hitty times.

The community you're thinking of is in Sudbury, Ontario. It's a couple of years old at this point but I have not heard any results.

I agree on keeping away from a septic system. That can be pretty messy if you're in a heating dominated climate and you freeze things.

Seems like a reasonable idea to me...

I am looking at a piece of property to purchase ne3xt year. It is in the back of a neighborhood and has a house with 5+ acres. There is room for Geo on the property... I am interested in how to set up a Geo system.

i seem to remember either reading or hearing about planned geothermal communities doing this very thing with a specially developed 'coaxial' sewer pipe. It may have even been overseas, but it would be very interesting to see it work. I wouldnt do the septic thing as freezing your tank, inlet, outlet, or leach field would really be $hitty times.

Originally Posted by trouble time

Try to get the pipes coming out of City Hall, I am sure you will get the right amount of excrement you need to heat the planet.......

Not anymore. I think it's all backed up these days.

Try to get the pipes coming out of City Hall, I am sure you will get the right amount of excrement you need to heat the planet.......

i'd just throw this out there. with all that crap and crud on the pipes, i'd wonder about longevity of the piping system, just a thought, but interesting idea!

There were some studies and actually homes modified so that all of the waste heat from the drains were tied into a heat exchanger that preheated the water going into the hot water heater and it really saved a bit of money/energy.

But the costs for installation were pretty high. Still, one heat exchanger located inside the home at the main outlet of the home sure would extract some heat from all that hot water going down the drain, I would think. That would elimanate all contact with the local sewer authorities but would bring you face to face with plumbing inspectors.

I was thinking of using the main lines of the municipality. Is there a rough rule of thunbas to how much pipe you would need per a ton of heating or cooling.

Dont think you could fit 3,400 ft of poly pipe in a septic tank.

One issue with using your sewage system as a heat source - removing too much heat could lead to an increase in viscosity of the sewage, interfering with flow and ultimately making it easier for the system to have freeze problems.

Not being familiar with sewers or septic, I also wonder if reduced temperatures in a septic system could interfere with the natural bacterial processes that break down the organic materials in the sludge (or whatever you call it).

There are variables to temp but for the most part in my area 55 would be average. It has been a while since I have looked at temps for I usually am looking at depth and velocity. I can get solid numbers this week if you would like.