Author Topic: Greywater heat recycler  (Read 4819 times)

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Larsmartinxt

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Greywater heat recycler
« on: January 04, 2014, 11:36:10 AM »
Over the past few year I've been thinking alot about greywater heat recycling.
As showers use a lot of energy it would be sensible to try to get back some of the heat washed down the drain.

Anyway here is a brief summary of the project:

Instead of feeding the water from my recycler to to the inlet of my water heater I opted to just run it to the cold water. The thermostat in the shower should regulate the water so that less water from the water heater is used when running the recycler.

I also opted to run the copper coil inside the drain pipe in direct contact with the grey water as opposed to making a new grey water drain pipe out of copper as I believe this is more efficient.

I used compression fittings so no soldering was involved.

Diagram of my greywater recycler


6 meters of 12mm copper pipe was coiled to form the heat exchanger inside my 75mm plastic drain pipe. This coil was made by filling the pipe with salt and then wrapping it around a pipe.



The coil was put inside 75mm drain pipe with y splits for the inlet and outlet of the coil.


View inside the heat exchanger


Heat exchanger in place


Cold water line connections to the bathroom. Inlet on left side outlet on right. I also made a bypass valve so I could disconnect the heat exchanger while still having a functioning water supply.


As of now I have not done any measurements of the efficiency of the system, but while running the shower the water in to the heat exchanger is very cold ~7C and the output is warm ~20C.



Lars
« Last Edit: January 04, 2014, 11:47:15 AM by Larsmartinxt »

Larsmartinxt

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Re: Greywater heat recycler
« Reply #1 on: January 05, 2014, 02:01:43 PM »
Measured some temperatures today.

Temperature to the exchanger


Temp from exchanger



MaryAlana

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Re: Greywater heat recycler
« Reply #2 on: January 05, 2014, 02:23:26 PM »
I see an issue... you are going to have all kinds of hair clogs if anyone in the house has long hair. Or anyone runs something down that drain they shouldn't.

thirteen

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Re: Greywater heat recycler
« Reply #3 on: January 05, 2014, 05:05:37 PM »
Do you have an on demand water heater?
Options:
1 Run the gray water under the incoming line and wrap it will  transfer heat no hair clogs
2run the gray shower water into an old water heater plumbed thru the middle of  it. It will preheat the incoming water.
3 If you do not insulate it will add heat to  the house
4 run the exhaust of your on demand water heater  thru the center of an old gas water heater plumb it into your incoming line 
just a few ideas to ponder.  13
MntMnROY 13

Larsmartinxt

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Re: Greywater heat recycler
« Reply #4 on: January 05, 2014, 05:48:21 PM »
I see an issue... you are going to have all kinds of hair clogs if anyone in the house has long hair. Or anyone runs something down that drain they shouldn't.

I can see the issue.
The drains going to the heat exchanger from the bathroom (2 of them) all have screens + traps that will filter out most of the hair.
Also I did make the exchanger so that it would be easy to take out for cleaning.
As of now there is no consistent long hair contamination  ::)
 
The passage  through the copper coil is around 50mm which around here is a normal size for shower drains.

I'll see how it behaves after some use.

Do you have an on demand water heater?
Options:
1 Run the gray water under the incoming line and wrap it will  transfer heat no hair clogs
2 run the gray shower water into an old water heater plumbed thru the middle of  it. It will preheat the incoming water.
3 If you do not insulate it will add heat to  the house
4 run the exhaust of your on demand water heater  thru the center of an old gas water heater plumb it into your incoming line 
just a few ideas to ponder.  13

No. I have a ordinary electric water heater (200L)
In Norway almost all water heaters run on electricity.
The problem with storing grey water is that it will form sludge at the bottom of the tank that will need regular cleaning. Also where the system is (crawlspace under my house) I don't need any heat.

Anyway.. many great ideas!

Lars