Principles And Construction 8:
The Planters 1

How The Planter Works

This page describes how the planter works. The next few pages show the construction of the planter.

The planter is a trough built just under the windows along the front of the house.

The planter has an inlet pipe, which accepts greywater, and an overflow pipe, where excess greywater can exit. Between these, large rocks cover the bottom of the planter; water can move from the inlet to the overflow between the rocks.

The bottom of the planter slopes gently, with the inlet end being higher.

The inlet pipe connects to a bucket. Greywater flows into the bucket, where sediment settles to the bottom, and scum floats to the surface. The inlet pipe has a filter as well, which must occasionally be cleaned. The bucket rises to the surface of the soil, and is normally kept covered by a lid.

The bucket has an outlet pipe leading into the planter. A tee fitting on the outlet pipe prevents surface scum from entering the outlet pipe.

The outlet pipe slopes to a vertical standpipe, which leads down to a distribution pipe at the bottom of the planter. The standpipe extends to the surface of the soil and has a cap which can be removed for inspection. The level of the water in the planter is visible in this standpipe.

The distribution pipe has holes in its sides and an open end. (The rocks in the planter are arranged so that they do not block these openings.)

This particular planter is long and narrow, so water will easily flow across its entire width. Wider planters such as the other two in the Potters' house have baffles which make sure that water flows under every part of the soil.

When the planter is in operation, the plants' roots grow down and take up the water. Water leaves the plants through their leaves, which pulls more water up from their roots. In this way, the plants transport nutrients up their stems, and use most of the water in the planter.

Any water which is not used by the plants exits the planter through the overflow pipe.

The overflow pipe has a standpipe like that at the inlet, but there is no bucket. Instead, the overflow pipe is connected directly to the standpipe, and slopes out of the house through the wall to the underground leach pit.

There is an angled cleanout pipe connected to the overflow pipe, which allows access to the pipe running through the wall, so that it can be cleared of obstructions such as roots.

The planter is lined with a waterproof membrane. Chuck used plastic vapour barrier backed by old billboard material.

The planter is filled with carefully-ordered layers of rocks, sand, and soil. At the bottom are large rocks 10 or 15 centimetres in diameter. Water flows between these. Above the large rocks is a layer of smaller rocks, a few centimetres in diameter. Above the smaller rocks is a layer of gravel.

Above the gravel is a layer of newspaper or geotextile, placed to block the openings between the rocks. Chuck used newspaper. Above the newspaper is a layer of sand. And above the sand is topsoil.

Next: preparing and lining the planter.

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