I’m working with an organization in the tropics that wants to set up a demo system of a kitchen greywater (or blackwater) system. They have varying levels of use, sometimes getting dozens of people in that food is prepared for, and sometimes having only a small staff there. They have a pretty elaborate system with a grease trap (which I suggested that they add microbes to), a long pipe, another trap/baffle, and then into a concrete gravel pit where a few plants are planted. I think that a more sustainable system could be created. It’s worthwhile doing this right because lots of locals see this system and  most everybody just lets their greywater pour down the hillside into their mountain spring systems. Problems they’re trying to solve are:

1. Intermittent light/heavy use

2. Containing the water so it doesn’t get into stream systems (soil is very well draining volcanic rock)

3. Making it simple and affordable enough that people will actually do it.

4. They get lots of rain most of the year, but their dry season can be very heavy use of kitchen which is good.

There are many organizations (hotels, etc) that need to create some kind of workable system. There are also many individual households that could use a simple system. So they could do both kinds. They could branch off of the existing system into a set of trees or ? I don’t think they need to concrete everything in – they have three tanks, one is an overflow with nothing planted in it .


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It does sound like this site could improve their design and how a more replicable option as well.

I have a few thoughts/ideas.

Planting a lot more plants  in the tanks would be a good way to evapo-transpire some of the water. Since they have high-use times and don’t want excess water to drain too quickly into the ground it seems like keeping the tanks is a good idea. For lower-use times, and/or for the overflow, they could install a simpler system without the cement tanks. Like you said, direct the water to a planted area of trees, and use tees to divide the flow. In the book, Create an Oasis with Greywater, there is a description of a gravity flow system in a tropical environment, using tees and local materials.

People who have lower flow situations (and who are currently dumping the water directly) could install a gravity flow branched drain system and direct the greywater to water loving plants.

This webpage (in spanish) shows a design for irrigating a banana circle. Their design uses subsurface irrigation, but you could instead direct the water to the top so it will filter through more soil.


Hope these ideas help!


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