Wash station filtering

I just moved into a new house and want build a wash station so I can wash/rinse awkward stuff like washable hvac filters, cat boxes, window screens, dogs etc.

I’ll be using plant based soaps when needed but what can I build that will help filter the grey water. The area won’t be close to food plants but the stuff in cat waste make me want to ensure it won’t contaminate the area (I clean out the boxes about 3-4 times a year)

One way to approach this would be to guide the water into the dedicated reedbed/WET system: a collection of aquatic and semi-aquatic plants that are able to tolerate high levels of nitrogen (e.g. cat faeces) and remediate the water by utilising the nitrogen and oxygenating it. That water system would need to be isolated from the rest of your greywater and well away from any edibles, but it's a nice, zero-input method for dealing with this kind of waste.

The specific plant choices for such a system will vary depending on your climate. Some options might be willow or poplar trees (high biomass yield), comfrey, bamboo, banana (yield of large leaves for mulch - I wouldn't eat the fruit but I am sure some would), Typha species (bullrush), Phragmites species (reeds).

The shape and size of the system would need to be designed to fit the volume and contamination level of the water. I've seen small (~2 meters diameter) "banana circles" for filtering urine and washing water. I've also seen much larger systems (~1 acre) for household grey and blackwater.

A final consideration is whether other animals are able to access to water before it has been filtered and remediated by the plants. Some designs for these system use a sequence of ponds with a slow flow-rate between them. The water in the top ponds will be much dirtier than those at the bottom. It might be wise to cover the top ponds with a mesh (hardware cloth, I believe it is called in the US).

Whatever solution you settle on, do post it here for others to find. I can imagine doing something like this myself some day soon.

Thank you, Luke!

I was trying to remember the name of a reed bed lol

I don’t think it would be too large since it will only be used maybe 1 day a month and hopefully only a few gallons at a time.

I’ll relook up reed beds and add it to the plan!

I had some outdoor wash stations before.

If I wanted to do one for items like you are suggesting I would make a french drain for the water to drain in.

A trench filled with rocks/gravel and then covered with dirt would work for me.

We use two of these french drains for our kitchen sink and our washing machine.

That’s a good idea!

I could do a French drain and use some of the plants that tolerate high nitrogen around it so it not just lawn or bare.

If you can manage to build one, I would prefer the "reed bed" system, which will have lots of microbes to actually eat the nasty stuff and turn it into plant material, than the French Drain system which depending on how it's built, will deposit the contaminated water deep enough that there will be few microbes and less active growing roots.

When I read the Humanure Handbook, Mr. Jenkins was really clear about his concern that traditional "dig a deep hole and poop in it" system can create a plume of contaminated water/soil under the ground. There's a reason that old-fashioned out-houses must be a certain distance from wells, and down-slope from them! Most of the toilet alternatives are trying hard to keep the liquid above or near the surface where there are lots of microbes and plants to suck up it up.

I have an intermittent use outdoor sink where I process ducks. The drain hose empties into a small ditch with nettles, bracken, lots of wood chips, and a big cedar tree. It's not a spot anyone would need to walk.

Jay Angler wrote:If you can manage to build one, I would prefer the "reed bed" system, which will have lots of microbes to actually eat the nasty stuff and turn it into plant material, than the French Drain system which depending on how it's built, will deposit the contaminated water deep enough that there will be few microbes and less active growing roots.

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I have an intermittent use outdoor sink where I process ducks. The drain hose empties into a small ditch with nettles, bracken, lots of wood chips, and a big cedar tree. It's not a spot anyone would need to walk.

I second that - a French drain is a useful tool, particularly for use around foundations or to dry out wet land, but, in my mind at least, it is more effective for removing and transporting water than for cleaning it up. If you were worried about contaminated water spilling around your wash station, you could use a french drain under that area to direct the spill towards a reed bed.

As for planting in such a way that discourages people from walking or playing there, that sounds like a good idea too. Of course, you could put up a simple barrier (a wooden fence or hurdle, perhaps) that would do the same job.

I really like Jay's and Luke's suggestions.

The french drain could be dug where it gets deeper at the end to flow into a reedbed.

I found these posts that might offer some suggestions also:

https://permies.com/t/49851/Black-water-worm-composting-reed

https://permies.com/t/95197/black-water-system

Yeah, I was thinking of combining the ideas since it will be fairly close to the house. Push the water away from the house with a French drain style system then use the plants to filter and create a barrier.

I don't have the climate for reed beds or constructed wetlands. In the summer here it's way too hot and dry and the winters are far too cold and snowy. Mountain life!

But what I do use is just a box full of wood chips, a few inches wider than my flat blade shovel and about four feet long. Water goes in one way and out the other, and all the gunk gets caught up in the wood chips.

Chips get shoveled out and thrown onto a compost heap. If you compost things long enough, short of heavy metals and petroleum, everything breaks down eventually.

Tony Hawkins wrote:what I do use is just a box full of wood chips, a few inches wider than my flat blade shovel and about four feet long. Water goes in one way and out the other, and all the gunk gets caught up in the wood chips.

That's a nice, simple and low-tech solution!

Tony Hawkins wrote:If you compost things long enough and hot enough, short of heavy metals and petroleum, everything breaks down eventually.

I'd like to add your quote though - I think plenty of pathogens can linger if the compost heap doesn't reach a decent temperature (~63 degrees C, the pasteurization point). If the compost is cool enough that weed seeds survive, it's not reach this critical temperature.

With regard to catboxes, there is the risk of Toxoplasma gondii (the toxoplasmosis parasite) which is not remediated or killed by any ordinary environmental processes. Be extremely cautious about introducing this into your outdoor environment (particularly waterways), as it is transmissible to humans and other animals.

See Basic Toxoplasmosis Information from CDC, and also Research into environmental toxoplasmosis transmission worldwide.

Yep, my wife is immune compromised and want to triple ensure we aren’t growing anything near the area that’s edible. I want to push this far away from the house anyway so the French drain and having plant barrier is key.

It won’t be going into any waterways.