Using greywater (graywater) for trees.

[esarratt]

I figure someone here has done this or knows who has.

Has anyone used graywater (greywater) from a household to water trees?

By graywater I mean kitchen sink, tub and bathroom sink water.

I am a North Carolina State certified septic installer.  You would think that this would be a part of our training, but it is not.

I am designing my home's septic system to separate greywater from blackwater (toilet waste).

The blackwater will go to the septic tank for treatment.

And some (or all) of the greywater will be used to water trees.  I don't want to overload the tree with phosphorus and other nutrients.

1) Does anyone know how much greywater can be used on a tree?

2) Does it vary by species?

3) Does it vary by the season of the year?

4) Can you point me in the direction of any books, research or people who might have the answer to these questions?

What I don't put on the trees will be filtered of solids and distributed to the soil in a long French drain.

I also plan to speak with the cooperative extension agency and NC State's soil science and agricultural department.

Thank you for your suggestions and advice.

[whiskers]

don't recall ever taking a dead root or dead tree or shrub from a septic field. I've run dishwasher/sink and washing machine water to a separate field without harming the grass. a grease trap might be worthwhile. 

[Southside]

Many dairies that don't have a manure lagoon will run their sink and tank wash water into a tank which gets directly irrigated onto grass with no negative results as long as it's applied in a reasonable manner.  

[KEC]

Are you sure that the trees really need supplemental water? I think that in my area, Onondaga County, NY, that the codes mandate that drain water must go to the septic tank.

[mike_belben]

A few months ago i repaired a neighbor ladies gray water line that had been run over by a tractor.  Because the area was so completely saturated in gray water at all times that the tractor sunk in over a foot and crush the pipe.  Even with good slope.


Im sure many trees cannot handle being as wet as a family of 4 would keep a place.  Id think beech maple poplar maybe alright with it.  Perhaps have several lines going in several directions to divide the flow rather than combine every appliance into one lane.  

I know my next door neighbor also has a gray line onto the lawn slope.  There are some stumps there he has been burning out over time but i dont know if the water killed them.

[Ianab]

Too much water and you drown the root system of pretty much any tree, except maybe willows or swamp cypress?  I think they are thinking more about trickle irrigation or running a hose for 5 mins a day?

There should be nothing in "grey" water that's harmful to trees, diluted as it is. Modern detergents are basically an oil molecule with an ionic "salt" on the end. It's designed to be broken down by natural bacteria in a septic tank (or soil), only leave some sulphate or phosphate. Hence why tree roots want to get into waste water pipes. 

Thing to watch for would be run off into any natural waterway. Aquatic critters are much more susceptible to detergent in the water. At least until it's been processed by those septic / soil bacteria.  

[Erik A]

It is (was?) legal in CA! Go figure. Haven't checked in a while on legalities. I have read don't water a garden with grey.

I think I would put in a valve to bypass and go into the septic.

One other thing if you are trying to get more use from your water, I have seen systems that use grey water to flush, not big savings, but?.....

[Don P]

I suspect this was part of your training  :D
There are laws in I believe every state... again enforcement varies. My understanding of the basic gist is you need another septic system for the greywater, it cannot surface discharge. Google NC greywater or similar, Extension or for us it is all done thru the health dept. There needs to be provision to direct flow to the main septic system... washing diapers in the sink or tub, etc. I looked into it here and it was not in the budget to comply with the rules for a code greywater system. More than a few I've seen are like Mike described, pigs living in a mud puddle.

[WV Sawmiller]

  We used treated blackwater for IW (Irrigation water) in Saudi Arabia. We used graywater in Mongolia for dust abatement on the dirt roads with no problem. We were allowed to dump our grey water directly into Coyote Creek on Bagram in Afghanistan with no noted problems.

   I am sure every family's grey water is different depending on the type and amount of soap and detergent they use in their kitchen, bath and laundry. I'd think in moderation you would just be irrigating and fertilizing your plants. I have no data but I am confident different tree, shrubs, flowers and grasses have different tolerances.

[reride82]

I'm not sure about NC, but in Montana Gray water can be used for plant irrigation as long as it is subsurface, and only watering plants not destined for human consumption. It still needs to have the appropriate setbacks from wells, surface water, and floodplains. I would say the volume per tree would vary greatly on tree species and maturity. A mature hardwood tree can take way more water than an ornamental yard tree. Soil type will also affect the amount of water per outlet as well. I would talk to your local sanitarian and go from there.

Levi