Rethinking Our Greywater System: A New (Much Improved) Plan

| 8/31/2015 4:25:00 PM

The Small Home, Big Decisions series follows Jennifer and her husband, Tyler, as they build a self-reliant homestead on a piece of country property in northeastern Kansas. The series will delve into questions that arise during their building process and the decisions they make along the way. The posts are a work in progress, written as their homestead-building adventure unfolds.

Even the best-laid plans have to change sometimes. This has proven true many times over in our home-building process. Whether to meet budget restrictions, work around inclement weather, or choose a more sustainable process, we’ve reworked our house plan in several ways over the past months of construction. A good, recent example is our greywater system.

We originally planned to pipe the greywater from our laundry system and simple wash basin in the basement out to some storage tanks that would sit slightly downhill from the house. The section of pipe out of the house would be buried (see the marker of where the buried pipe ends about 20 feet from our house in the image above), but would eventually come to the surface for the water to run into the storage tanks. Then, we decided to add the water from our kitchen sink and dishwasher into the greywater system, both of which are directly above the basement laundry area. That way, we wouldn’t have to run any water lines from that side of our house over to the septic system on the other side of our house (the side where both bathrooms will be located). This would allow us to reuse even more water for keeping our landscaping hydrated, and the more water we direct to this greywater system means less for our septic to deal with. Great idea, right?

Turns out, it’s not so simple. After doing more reading on the potential problems that can arise when you wash foodstuffs (think raw meat and bacteria) or lots of sediment (think soil-encrusted potatoes), we decided we couldn’t just pipe the water to storage tanks. We didn’t want to risk creating a pathogen nightmare or having to unclog dirt and sediment buildup. Add the complications of what in the world we’d do in winter when the ends of the pipes and the storage tanks would be exposed to freezing temperatures, and we realized it was time to do some reorganizing.

We’ve decided we want the greywater pipes outside of the house to be buried, and any water they carry to be released underground. To prevent this water from washing away subsoil, we had read about and considered installing mulch basins that slow the water down and help concentrate it in areas where you want to keep it (such as around the roots of trees or bushes). We’d also read about some that operate like a mini-septic system, where you dig a trench below the frost line, lay out a gravel field (likely covered with some leftover housewrap to help hold it all firmly in place), set a perforated pipe over the gravel, and bury the whole system. We decided to go with the latter option, because we can lay the perforated pipe perpendicular to the downward slope (see planned pipe location below) that runs away from our house and into the wooded area behind our home. We plan to plant a small orchard in the area downhill from the pipe, which would stay moist underground as the water naturally flows down the slope. We use homemade, nontoxic dish and laundry cleaners, and will use a filter at each sink to prevent much dirt or any chunks of food from heading down the line and clogging up our system.

4/13/2018 9:05:12 AM

Rjo, I believe you installed the grease trap backwards. the out flow should be lower than the in flow to "TRAP" the grease and oils on the top of the water in the trap. You would pull the water from under the floating grease and oil.

9/12/2015 1:58:21 PM

I installed a grease filtering system for the kitchen sewer, outside of our church. It was made from a 36" tall by 24" dia. concrete culvert pipe set vertical in the soil, using concrete to seal the bottom and a metal cap on top. An internal baffle (PVC elbow and pipe turned downward for output - exiting the culvert higher than input) creates an internal pool of grey water and causes fat and oil to float. Fat is removed as needed. One can filter or trap sediment in a similar trap and clean the trap as needed.

9/11/2015 5:22:26 PM

Thanks for the tips! We'll keep that in mind, and watch closely.

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