Green Concept Home - 2/1/2010

Today was the third tour of my multiple tour series of the Green Concept Home.  We had a great turnout, 7 new tourists joining us for the first time.  Things have really progressed since our last tour about 6 weeks ago.  House is wrapped, framing inside is complete, windows are in, plumbing rough-in is done and the siding will be going on soon.

Our tour today was focused on the underground cistern which the Green Concept Home will utilize to harvest rainwater for outside irrigation and for flushing the toilets inside.  It will NOT be for potable usage.  In our orientation with David Huang (owner & designer), he told us that obtaining the permit from the city of Bellevue for the underground cistern was an absolute nightmare!  Because of this relatively new builing practice here in Bellevue, the city was not prepared for this request.  They probably had to consult the city of Seattle or other neighboring building departments to know how to handle such a request.  I guess I can cut the city of Bellevue some slack, being that this was their first one, they probably wanted to make sure they dotted their i's and crossed their t's before giving the green light.


David instructing the "Greeen Tourists" on the operation
of the cistern.

The cistern being used is a 1,700 gallon polyethylene tank.  Polyethylene is an extremely durable and long lasting material commonly used for outdoor products. The use of polyethylene with U.V. inhibitors in the manufacturing process ensures the longevity of the tank.  The rainwater that is harvested from the roof gutter system feeds into a filter system (fig. 1)  The first stage removes larger debris such as leaves and other organic matter which protects the finer second stage from clogging.  After the finer particles are removed in the second stage the clean water flows into the cistern tank through the 4" calmed inlet (fig. 2).  Once the water is inside the cistern tank, there is a floating suction filter (fig. 3) which prevents sediment and foreign matter from being suctioned out of the cistern. No extra suction resistance is caused through the larger filter surface with this fine filter. This means the pump can develop its optimum effectiveness. The ball float allows the suction point to rise and fall with the water level and ensures that the water is taken where it is most clean: just below the water surface, an important component for any irrigation or toilet flushing application.

 
Fig. 1 - In-ground filter


Fig. 2 - Calmed inlet pipe from filter


Fig. 3 - David explains the function of the
floating suction filter