Greywater Filter Upgrade

The water draining from my shower pan into the 11 gallon container that rolled under the house had to be drained and distributed once a week. This water I would use to irrigate the garden. When I mentioned my system to my permaculture group it was pointed out to me that grey water that sits in a tank for more than 24 hours becomes classified as black water because of the growth of bacteria past that time period. I did not know this. I would more describe it as brown and the smell was minimal unless mixed with urine, then it could amplify the smell of urine to noticeable detection. Not optimum in a dense suburban neighborhood. 

Once my attention was drawn to this factor I cut pipe to attach to the drain and had the water directed to the bare ground away from the cement pad directly below the drain. During the dry summer months the ants crawled into the pipe and into my house. They had not crawled in so easily before because the drainpipe did not touch the ground outside and there was a sizable gap between pipe and the 11 gallon container on wheels. I thought to have the pipe disconnected and the water fall onto a receptacle. I began to research bio filters on Pinterest and once I grasped the concept I could design one to fit my situation.

 A bio filter allows water to fall onto its surface much like rain. A layer of sand filters the water of organic matter. But it can't just be all sand because the sand would drain out too. Plus it would take a long time for water to filter through so much sand. So a layer of small pebbles supports the sand and under that a layer of larger pebbles supports that. I just needed the right size container to fit under the house on a platform that would be raised high enough to allow drainage through the pipe.

I found a 5 gallon plastic storage box with a lid that was recessed. This served to hold water rather than shed it. Then I drilled holes at all the intersections of the grid pattern. Later I realized the holes were too big and too far apart to simulate rain so I drilled many more smaller ones.

I also had to drill a large hole in the bottom of the box and find a pipe fitting to connect the drainage pipe to the box so it would be water tight. There are not many options here because the connection has to make contact with the walls of the box on both sides. I eventually found such a fitting in the electrical department for making water tight outdoor connections between electrical boxes in commercial buildings.

The next step was to add my layers of large pebbles. 

Then small pebbles.

And finally the layer of sand.

Once the filter is in use a layer of microbes grows over the sand and eats the organic matter so the theory goes.

Here is the filter in place under the house. I happened to have a wooden platform on wheels from another project to put it on. I then placed a plastic scrub sponge under one end to give it a little drainage elevation.

It appears to work perfectly. 

To assist with screening cooking fat (and large bits of food) I had already made a filter of straw that sits in the drain pan inside the house. I used an old collapsible water tote I had for camping. I cut the top of it to make a hatch for putting in the straw. I also directed the drain hose from the sink into it. The filter is shown here with the spout visible. This straw is replaced every week or so and used in the garden as mulch. The filter also serves as a compost bucket so I no longer needed the one I was using. I found that the spout would clog up way too often so I removed it and eventually replaced it with a rubber funnel (actually a diva cup I no longer used, heh).





For a more finished look I made a cover from some silver vinyl to go over the filter.

The whole system took a lot of problem solving to work out all the details and to think of what I could use for each part of it. If there was more room under the house the straw part of it might be preferable outside, but I don't mind it inside once I had a cover for it. It makes it easy to change the straw plus being a compost bucket. 

The best thing about this upgrade was that I no longer had the considerable weekly chore of dragging out the 11 gallon tank and draining water into buckets to distribute. Such a drainage tank would be more useful if I were traveling with the tiny house which is unlikely so the tank is in storage and I would be happy to part with it if there was someone who could use it.

(This post has been backdated to keep a record of the timeline. Actual date of writing is 12/23/18).