Sunday, October 09, 2011

Fixing the graywater tub

Earlier this year, I described our constructed wetland for graywater treatment, and mentioned problems with much of the water infiltrating through the dirt instead of overflowing into our second tub. Today I attempted to correct the problem.

The Problem

This picture shows the upper edge of the hot tub which I buried in the ground. I "planted" the tub too low, so we added lots of soil around the edge of the tub, and wood chips on top of the constructed wetland. The wood chips broke down into lovely soil, and it all wicked water out of the tub and into the surrounding paths. Small flows of water from sinks, even prolonged activities such as washing dishes, never made it into our second tub of "treated" water, so we never got to use most of our water for irrigation. We only got water overflows when we took a shower.

The white pipe in the photo carries graywater from the house and deposits into the tub.

The Solution

I dug around three sides of the tub, exposing the upper edge, and removed 2-3" of dirt and gravel on the inside surface. I wiped that 2-3" of tub edge clean, then squeezed a bead of PL Roof & Flashing Sealant onto the cleaned edge. I cut some scrap pond liner (left over from our ecoroof projects) into approximate 3 1/2" - 4" tall strips, and pressed it into the sealant bead to effectively raise the waterproof edge of the tub by about 2 1/2" on three sides. I did not raise the fourth side, where the water is supposed to overflow.

After the sealant cures overnight, I'll refill the interior of the new pond liner extension with gravel, and bring dirt back up to the outside edge of the pond liner. This should prevent the worst of the "wicking" and allow water to overflow as originally planned.

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