Water Recycler (Grey Water)

The area that I live in has been in a drought for a year or more. As such we now have water restrictions on washing the car, watering the garden etc. Initially I set up a drainage hose from the washing machine outlet to containers outside to enable me to collect the waste water so I could water the garden. This process worked fine except for the back breaking work of emptying the waste water (grey water) onto various places in the garden.

The next stage was to develop an automatic system that would distribute the grey water into the garden and have the following features.
1) Filter the water before sending it to the garden.
2) Automatic pump to allow water to be delivered to the high end of the garden.
3) Timer to prevent water stagnating in the tank.

The system uses a wheeled trash bin which is made out of 5mm thick plastic (nice and sturdy). Grey water comes into the top of the bin into a filter. When the bin fills to around 3/4 full, a water level switch triggers the pump controller to turn on the pump sitting at the bottom of the bin. The pump continues to operate until the lower water level switch is triggered.

The pump controller also has some logic built into the program to detect if water is in the bin but not high enough to operate the high water level switch. If this situation occurs, at 10 hour timer is started. If the water stays in the bin for 10 hours the pump will start and empty the bin. This stops the water from stagnating. I also have another timer that detects the run time of the pump. If the pump runs for longer than an hour (without any of the level switches being triggered) then the fault LED will be lit and all pumping will stop. This would indicate that the output pipe is blocked.

The pump controller is built around a PICAXE 8m PIC. The reason I chose this particular PIC is that it is programmed in BASIC and is cheap ($4 AUD) and I can't program in C to save myself.

There are 3 float sensor switches used in the project. Two of these float sensor switches detect high and low water levels of the tank. The third sensor detects when the water filter needs a clean.

The controller also drives 3 LED's that are mounted on a remote indicator panel in the laundry that indicates pump running, filter clean required & fault condition.

The transformer I used in the project has a 24VAC tap that I was going to use to power some water solenoids. Any voltage from 12VAC to 18VAC can power the circuit. The voltage regulator doesn't get hot as the PIC only draws a few milliamps. I also use a resistor to reduce the unregulated voltage to the pump relay which may need to be altered depending on the relay voltage.

Make your PCB. I used the tried and tested toner transfer method. The attached schematic & PCB were done in Eagle. I'm just learning Eagle so please excuse my mistakes. I placed vias on most of the pads to increase there size. I found I just couldn't get the DRC rules right so I found this method easier.

Parts List
1x 8 pin IC socket.
1x PICAXE-8M
1x 7805 5v regulator.
1x 1amp bridge rectifier.
2x PCB mount fuse holders for M205 fuse.
1x 500mA M205 fuse.
3x BC639 transistors.
12V relay with switch contacts rated at 240VAC 10 Amps.
3x 3way PCB screw terminal blocks 5mm spacing.
2x 2way PCB screw terminal blocks 5mm spacing.
1x 1N4004 diode.
1x 1000uf 35v (or higher) electrolytic capacitor.
6x 2.7K resistors 1/4 watt.
3x 10K resistors 1/4 watt.
1x 100nf ceramic or mylar capacitor.
1x 180ohm 1 watt resistor - note resistance and wattage may need to be varied due to supply voltage.
2x 5mm green LEDs.
1x 5mm red LED.
1x 5mm amber LED.
1x weatherproof box to house the controller.
1x small box to house the 3 status LEDs.
4x waterproof cable grommets with internal rubber glands.
Various size cable ties, heat shrink.

Parts list for the PIC programmer circuit
1x 10K resistor.
1x 22K resistor.
1x 9 PIN female DB connector (this connects to your PC / MAC).

The PICAXE-8M is programmed via the serial port of your PC. The PICAXE editor and data sheets can be obtained from the following URL:-
http://www.rev-ed.co.uk

The code is easily modified however I didn't put any "in circuit" program headers on the PCB so you'll have to take the PIC out to re-program.

The schematic & PCB could be used for other switching / sensor purposes with the required code changes made.

Here's the BASIC code:-

;Grey water controller MK2

symbol PUMP=0 ; name output 0 as the PUMP
symbol ERROR_LED=1 ; name the output 1 as the error (fault) LED

;high waterfloat switch = input 3, low water float switch = input 4

let dirs=%0000111
let pins=%0000000 ;ensure all outputs low

;float switches are inverse logic, a 0 means it is turned on
main_loop:
if input3=0 and input4=0 then debounce ;high water float mark
if input4=0 then inc_timer ;low water float mark
goto main_loop

inc_timer:
let w0=w0+1
if w0=36000 then start_pump ;if water is in the tank for 10 hours, start pump
pause 1000 ;pause 1 second
goto main_loop

debounce:
pause 500
if input3=1 then main_loop ;check if the float is still high

start_pump:
high PUMP ;turn on pump relay

pump_loop:
if input4=1 then stop_pump ;check to see if low water
if w1=3600 then pump_error ;error if pumps operates continuously for more than 60 minutes
let w1=w1+1
pause 1000
goto pump_loop

stop_pump:
low PUMP ;stop pump
let w0=0 ;reset stale water counter
let w1=0 ;reset error counter
goto main_loop

pump_error:
low PUMP ;stop the pump

error_loop:
if input4=1 then exit_loop ;stay errored until tank empty
high ERROR_LED
pause 500
low ERROR_LED
pause 500
goto error_loop

exit_loop:
let w0=0 ;reset counters
let w1=0
low ERROR_LED ;reset error LED
goto main_loop

I set up the following circuit up on a prototyping board to program the PIC.

The pump I chose was a submersible type designed for dirty water. It was suppose to operate in the vertical position but it would not reliably deliver water after a few months of operation. I tracked the issue down to air in the impeller chamber. There was a small ball bearing that was suppose to let air escape and close the bleed hole when the pump was running. However grey water has soap in it. After some months this ball bearing was stuck in its hole preventing air escaping from the chamber.

The solution was to put the pump on its side to prevent air pockets from being created. A year later I think this mounting method was not in the best interest of the pump. The pump seems to have lost its punch, it still delivers water but not like it use to. I suspect the pump being on it side has let water seep into the motor bearings (only a theory).

The pump is mounted on a aluminum frame. The frame is secured to the bin at the top of the frame. This was done so that the bin is watertight. Any mounting holes in the bin are above the high water line. Also mounted on the aluminum frame is the 2 water level switches. These are sealed magnet & reed switch units and can be purchased at spa shops or here in Australia at Jaycar http://jaycar.com.au or Altronics http://www.altronics.com.au.

To stop the pump from sliding around at the bottom of the bin it is cable tied to the aluminum frame.

The following instructions show how to wire up the controller to the pump and remote indicator panel.

For the power cord I used a power extension lead and chopped it in half. This method left me with a molded power socket for the lead that goes to the pump. That way I didn't need to butcher the existing power cord on the pump. Alternatively you could mount a power socket on the case of the controller.

Please ensure that the earth wire (green/yellow stripe) is connected from the power cord through to the lead going to the pump. To join the earth wires together I used a crimp lug that was then bolted to the transformer chassis (using star washer to ensure a good connection to the metal).

The transformer I used had flexible leads so I crimped the 3 neutral wires (blue) together using an insulated joiner (then heatshrink was placed over it).

To connect the 3 LED's on the remote indicator panel you need 4 wires. You can use Cat5 or phone cable. I also had a power LED that is mounted in the controller box itself (not remotely).

The remote indicator panel is made from a hobby box that you can purchase from electronic stores like Jaycar, Altronics, Dick Smith, Radio Shack etc. The lettering I used was Letraset rub on lettering. The weatherproof polycarbonate box was purchased from an electronic supply store. Ensure that it can be sealed to prevent rain from getting in.

Since you will be having a pump that is submerged in water you must power the controller / pump from a safety switch protected power outlet. You can find cheap extension cords that have a safety switch built into the plug.

I installed the Grey Water recycling bin up the side of the house that has all the plumbing. The recycler needs a sewage inlet that the overflow pipe can connect to. It also needs a hose run from the outlet of the washing machine to the inlet (top) of the bin. You can connect your shower or bath to the bin but this would require major plumbing alterations. Also hear in Australia any permanent plumbing needs to be carried out by a licensed plumber. You also must not use the recycler for Black Water e.g. water from sinks & toilets for obvious smelly reasons.

The outlet of the recycler is feed into the garden via 19mm (3/4" I think) garden poly tubing. This is nice and cheap. In the garden I have buried slotted poly drainage pipe which the Grey Water empties into. You can't use sprinklers as the soap in the water will clog any small nozzles and also spraying the water could be a health hazard as any water left in the tubing will become stagnant. There is also the risk of inhaling waterborne bacteria so don't use sprinklers.

I have also noticed a range of low pressure drip hoses designed for tank water / gravity feed irrigation systems. I'm not too sure how long these hoses would last with the soap content in the water. They also could be used to deliver the water to the required locations in the garden.