Friday, July 5, 2013

Our DIY Grey Water Recycling System

I was lucky enough to participate in this one week course called Social Venture Design by the Indian Institute of Human Settlements and Acara Institute, University of Minnesota, here in Bangalore. During the course, I got to discuss our grey water recycling system with experts as well as people who share similar interests. It was a very inspiring and motivating week. At the end of the week, Ashwin and I decided it was time to "show" our grey water recycling experiment to the rest of the world. (We believe in Open Source!) So, here it is. Complete, with instructions. 

It is well known that washing machines consume a significant portion of a household’s fresh water use, which is typically sent directly to sewerage system. However this water, which is essentially soap and dirt with water can be used for flushing in toilets. What is described below is for a fully automatic, front loading washing machine, like ours. It can be adapted to other washing machines as well. 

Our Grey Water Recycling System
(On a side note, the laundry basket you see next to the washing machine was also DIY-ed with PVC Pipes!)

Equipment needed

1. 60 lts transparent , flat tank with dimensions 20”x 20”x11”– 2 no’s [one lower tank, one upper tank]

2. 0.50 HP pump – 1 no’s

3. 3 Way connector

4. 1“ diameter pipe , 2 metres

5. 1“ diameter pipe elbow connectors – 8

6. 1.5” diameter pipe , 1 Metre

7. Flush to inlet flexi pipes, 3 No’s , ½ “diameter and 20”length

8. Taps for fresh water and waste water , with place for outlet pipe to be fixed

9. Raised pedestal ( metal / stone ) for placing washing machine

10. A platform ( metal) of dimensions as tank to place it

11. Tools – hacksaw blade , power drill, adjustable spanner

12. Disinfectant/Cistern block – 2 no’s such as Harpic, or any other brand

13. Power outlet for pump

Some Assumptions

1.Toilet flush has a tank to store water

2.The washing machine has a permanent location and there is a way to reach the toilet flush tank from it. Here, the washing machine is located adjoining the toilet ( separated by a wall ) as shown

3.There is space to place the lower tank near the washing machine. If it would be placed below, a clearance of about 1.5 feet would be required.

4.There is space to place the upper tank, with at least 2 feet of clearance above the washing machine

The Layout

Schematic of our system. Steps given below


1. Place the washing machine on a flat pedestal either made of stone or metal. The pedestal should be able to withstand the weight and vibration of washing machine (any mason / fabricator will be able to make one as per this requirements). The area of the pedestal should be bigger than that of the tank, so that tank can be placed below. Ensure the washing machine has access to fresh water inlet after placing on pedestal.

2. Place the 1st tank(lower tank), below in the place created.

3. At about a height of 3 feet above the top of the washing machine place the platform for placing 2nd tank (upper tank).

4. Drill a hole in the lower tank close to one of bottom edges of 1 “diameter pipe for outlet pipe (1” diameter). This pipe will be connected to the pump inlet ( use instructions given along by pump manufacturer for these connections)

5. Drill a Hole in Upper tank to allow the outlet from pump to flow into it. Place a filter at this place. Place the outlet pipe (1” diameter) from the pump and connect it to Upper tank which has been placed above, make sure inlet to Upper tank is towards top edge of tank.

6. Provide power outlet and connect the pump to it.

7. On top of upper tank drill a hole and insert the 1.5“diameter pipe, and connect it to lower tank. This is to handle overflow situation in the upper tank. More water flows down to the lower tank.

8. Draw a pipe (1” diameter) from the top tank ( as close to bottom edge) and provide and outlet near the toilet flush, this may vary from house to house and will need the help of plumber to place this. As the two units are separated by a wall, this is a direct, single pipe connection.

9. Provide an outlet pipe at the cross section of this pipe with upper tank. This is important. In case of blockage in the pipe due to air or small sediments, by pumping water in the reverse direction, the block can be forced out.

10. Connect the 3-way connector with the flexi pipe from fresh water supply to flush, waste water from washing machine and then the common flexi pipe going to flush tank. Both fresh and waste water supplies will have taps at this point by which you can switch between the two based on availability of fresh/waste water

11. Place a disinfectant block each in both upper and lower tanks (for simple filtering)


1. Once a washing machine cycle is completed the water gets stored in lower tank , switch on pump , it will take 2-3 mins to pump water to Upper tank

2. Turn on the tap of waste water and switch off the fresh water supply and now your flush works on waste water from washing machine

3. When you are not running washing machine, (i.e. when the upper tank is empty) turn off the waste water supply and turn on fresh water supply.

So, there you go! Please do let us know what you think of it. And if you'd like us to help you install this system at your house, you could write to us. And we could "take it offline". 

Have a lovely weekend!

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Ashwidea by Preethy Iyer and Ashwin Subramanian is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License