Too Much Mulch Basin Filtered Greywater for Indoor Living Wall

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Hello, everyone!

My husband and I are in the process of designing our home to Living Building Challenge standards. Our home will be situated in central Pennsylvania, and we are attempting to meet the Water Petal of the Living Building Challenge while also adhering to PA state code. I can go more into the challenge further if anyone is curious, but I will cut straight to our conundrum: we need to keep all of the treatment and usage of our water within our home’s envelope to help meet code and the challenge.

Our current plan is to send our kitchen and laundry effluent to an indoor mulch basin below our home (basically, a clivus multrum composting tank converted to a mulch basin…). Once the greywater filters through the mulch, it will be pumped to a separate holding tank (also, still within the home’s envelope). From the storage tank, it will be pumped up to an approximately 108 square foot indoor living wall inside our living/kitchen space. The living wall will essentially act as our absorption field for all of our treated kitchen and laundry greywater. The plants will release the water through transpiration, and our ventilation system will kick the water vapor out of our home (thereby, no untreated effluent is leaving our home’s envelope and into the ‘grounds of this commonwealth’).

However….we are anticipating that our mulch basin will receive about 30 gallons of greywater per day from our kitchen and laundry. When speaking with a living wall manufacturer, the living wall will only need to be watered once every 7 to 10 days…and only 20 gallons would approximately be needed for each ‘watering session.’

Phew..so, the problem: our mulch basin is going to receive a disproportionately large amount of greywater in need of treatment each day, in comparison to the amount of water that our prospective indoor green wall is actually going to need.

Planting an outdoor greywater garden or living wall would break code. A greywater garden is not seen as a viable means of greywater treatment in PA, since PA does not differentiate between grey and black water in code.

I also had the thought that we could cover our home’s walls…every available interior foot…with a green wall. I do love green. But that seemed like too much…

We are attempting to orient the living wall in our home in a way that it would receive an ample amount of southern light…which could hopefully increase the overall thirst and health of our plants?

Soooo…yes. Any suggestions?

I am attaching a diagram of our intended water harvesting, use, and reuse system to this question!

Thank you!!!!

Shelby

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Greywater reuse- general Indoor GW Reuse living wall mulch basin Pennsylvania code Living Building Challenge

Shelby Aldrich asked 3 years ago

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Answers (1)

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Hi Shelby,

Sounds like a fun and challenging project!

My initial thoughts on your system is that it looks very complicated and seems like it will be hard to make it work well. I would definitely not want greywater going through a living wall in my home, especially from the kitchen. (kitchen water is gunky and prone to clogging systems)

I heard an architect present on this project that uses greywater on a living wall and my memory was the system was pretty fussy and they had a lot of challenges getting it all working smoothly. If possible, I’d talk to people who have done this before, and lived with the system (!!!!), before you decide if it’s the route you want to go on.

A potential alternative would be an indoor greenhouse. This would still be part of your living space (for code requirements), but would give you a little buffer if the system has any issues and would require less pumping and maybe less filtration.

I profiled these people’s home in my book, and interviewed them a few years back. I think this type of design would be a lot more likely to succeed then your current version, and this would be the way I’d go if it were my home. You would have a lot more evapo-transpiration potential from plants that can grow tall, like in a greenhouse, than from a living wall.

If you’re not familiar with Earthships, they utilize indoor greenhouse planters for greywater treatment. This may be a potential design option for you also.