We would like to install something for greywater. We purchased a lake home that only has a 1,500 gallon storage tank for septic.

Asked by Linda
Rockford, MN

Minnesota lake home with storage tank for septic. Grey water solutions?


Elizabeth DiSalvo

Answered by Elizabeth DiSalvo

Ridgefield , CT

Trillium Architects

August 19, 2013

Hi Linda,

Great question. You can take a huge burden off your septic system by using a grey water collection tank. They are relatively simple systems that are not that hard to install by a licensed plumber.

Basically a grey water system will collect water from bathtubs, showers or washing machines, divert it to the grey water system and filter it through a number of sequential filters (often in a stand alone ‘box’ that sits outside your home) and then releases the cleaner water to a drip irrigation system for your lawn or garden.

Some important things to remember:

  • Only wastewater from a bathtub, shower or washing machine should be sent to the grey water system. ‘Black water - or sewage – which is wastewater from other fixtures, such as toilets and dishwashers, often contains hazardous, illness-inducing bacteria.
  • Don’t water vegetable gardens with filtered grey water and don’t let pets or humans drink the grey water as it is not potable. It still may contain soaps and other low grade containments that can actually be beneficial to plants but not good for animal or human consumption.
  • Check with your local waste water officials to make sure you are doing work within code. You may also be able to divert your filtered grey water into a secondary buried detention tank that will slowly allow it back into the surrounding ground water.

Good luck. I think that this is a great idea and will help save your septic system!

Find a good and creative plumber who can work with a positive attitude and who will not tell you ‘its too hard!’ or ‘it can’t be done’. It may involve a bit of complicated plumbing or it may be quite simple.



For more information:

Read our backgrounder "Easy as 1, 2, 3: How to Recycle Grey Water."

Also, read "We want to design a greywater system for bathrooms we're renovating. Can you help?" a Q&A answered by Jesse Terzi.

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