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Different ways to reuse graywater

These are the commonly accepted methods of reusing untreated graywater:

  • Buckets
  • Branched Drain (or similar)
  • Laundry to Landscape
  • Gravity Dripperline
  • Pumped Dripperline

Before going in to the pro's and con's of each method, the concept of how much water is actually saved needs to be understood.

If you put 10 gallons of water in one 4' hole in the ground every day, you have not saved 10 gallons per day. In Tucson, Arizona, that hole only needs 12 gallons for the whole of July for medium water use plants.

If this was done daily, then 300 gallons has been irrigated over the month, instead of the required 12 gallons.

The actual amount saved is 12 gallons. The irrigation efficiency is 12/300 or 4%.

This may sound extreme, but I have seen quite a few branch drain systems set up this way (the rest of the water goes down into the subsoil and is wasted, unless trapped by clay in which case the roots of the plants may rot).

So while on the surface some methods may appear to be very inexpensive for the amount of water diverted, the amount of water actually saved needs to be reviewed.

Irrigation Efficiency Rates for Different Methods:

  Irrigation Method    Efficiency
          Buckets                50%
  Branched Drain   30%
  Laundry to Landscape   40%
  Gravity Dripperline   90%
  Pumped Dripperline   90%

 

The efficiency rates listed for branched drain and Laundry to Landscape methods are extremely generous, based on absolute best practice installation methods by highly experienced installers.

Cost / Benefit Analysis of the different methods.

After applying the irrigation efficiencies of the methods, determining how much potable water is no longer needed to irrigate the garden, these charts can now be presented.

If you would like the math behind the following charts, please contact us via the contacts page for more information.

cost_v_saving_water_reuse.jpg

Cost vs Gallons of Potable Water saved over 5 years

Assumptions:

Paid labour has been used for installation of all methods except for bucketing of water. A small amount has been added to the bucketing methods, for 1 chiropractic visit (this isnt a joke, it's an onging issue in Australia).

While voluntary labor (you) can be used to reduce the cost, the efficiency of Branched Drain and Laundry to Landscape methods will typically halve. Those interested in installing their own Branched Drain network should go to our videos page and review the branched drain installation video (8 minutes)

 

cents_per_gallon_water_reuse.jpg

Cost per gallons of water saved over 5 years use.

This chart illustrates how Dripperline irrigation is far more cost effective over 5 years (at about 0.5 cents per gallon) than even Laundry to Landscape at about 2.5 cents per gallon.

It all comes back to how much potable water (irrigation water out of the tap)
is saved by each of the methods of diverting graywater.

To read about pro's and con's of each individual technique please click here to go to part 2 of this article.