What is the best - cost, minimising negative environmental impact, simple - way to process grey water outflow?

I plan to build an off-grid cabin, I will be harvesting rainwater, using it in my sinks/shower with some 'eco' detergents and soap and then I am not sure what to do with it. We won't have a washing machine or dishwasher.

Can I just let it drain into the soil, how do I disperse it and how can I minimise the negative environmental impact?

I have read about reed bed systems but I would like to explore simpler, cheaper options as well. I'm in the West of Ireland and the soil is shallow and pretty wet for a lot of the year.

  • 1
    Possible duplicate of What are the cheapest and easiest methods to convert grey water to potable water?
    – LShaver
    Commented Dec 21, 2017 at 16:11
  • 3
    Not a duplicate, no interest in reclaiming grey water just in dispersing it. Interesting question tho.
    – welfare
    Commented Dec 21, 2017 at 17:22
  • These systems are very sensitive to local conditions. What is your climate, what soil types do you have available, what is your local topography like, what is the local hydrology you'll be interacting with? And what is your estimate for the quantity you need to deal with (as an approximation, how many people will be in the structure)? Commented Apr 1, 2018 at 12:34

2 Answers 2


I was faced with a similar question a couple of years ago. The best solution I could come up with was to feed the grey water into an area occupied by plants that consumed 'large' quantities of water and continuously dropped leaf litter. The leaf litter would layer on top of the particulates in the grey water and provide protection to the micro-organisms that break it down into plant-accessible form.

I ended up going with a combination of three different species of bamboo.

The bamboo sucks up all the water I can throw at it, ultimately consumes all the nutrients, provides shelter from the wind, offers shade in summer, grants privacy all-year-round, and in about two more years will start yielding a regularly-harvestable crop of culms that I can use for various purposes (e.g. chicken pens, alpaca shelters, gardening stakes, footbridges, biochar). Since I have no interest in eating bamboo shoots, this approach does not impact on my food chain.

I know you didn't say that you wanted to make use of your grey water, but I figured I'd let you know what I came up with in case that sparked some ideas. Dispersal is good... but crops are better!

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    Research would show two suitable books (among others) How to shit in the woods by Kathleen Meyer who explains reed-beds for treating water and Lifting the lid by Louise Halestrap & Peter Harper, whuch also expounds reed-beds.
    – Solar Mike
    Commented Apr 12, 2018 at 4:55
  • 1
    @Solar Mike I'm not sure why you posted that comment. The OP explicitly says that they have looked at and discounted reed beds, and I am talking about bamboo which provides a direct yield instead of reed beds that don't.
    – Tim
    Commented Apr 12, 2018 at 6:13
  • 1
    Perhaps because they may be useful references to some people prepared to read them... the do contain much more than just reed beds...
    – Solar Mike
    Commented Apr 12, 2018 at 6:23

One possible solution would be to construct mulch pits around trees, etc. and then discharge the greywater directly into the bottom of the mulch pits. The mulch pits will help decompose any grease/particles and the phosphates, etc. should help feed the trees. Select soaps that are low in sodium. Sodium can be toxic to plants in high enough concentrations.

The mulch will eventually break down into compost that can be used elsewhere and replaced with new mulch.

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