Solar Power isn't Feasible!

Solar Power isn't Feasible!
This cartoon was on the cover of the book "SolarGas" by David Hoye. It echoes the Sharp Solar slogan "Last time I checked nobody owned the sun!"

Saturday, August 30, 2008

Shades of Greywater in Technicolor

(photo: our Turkish-German friend Comert Solmaz, the solar plumber from SolmaTec, happily inspects the system we co-designed for making use of our "dirty" -- read "nutrient-rich" -- water to flush the toilet and water the porch garden)

Our friend and colleague, Utility Consultant Frank DiMassa, whom I recently toured Spain's solar thermal power towers and concentrator fields with, has one of the greenest "average American" homes I've seen in the U.S. -- all retrofits that he has done himself to guarantee his children a better future (It's not for nothing that he is on our International Solar CITIES board of directors! )

Frank recently sent me an email discussing ideas for another eco-friendly feature he would like to retrofit into his home: a "do-it-yourself" greywater system.

How pleased I was to hear from him, because Sybille and I and Comert, the plumber, installed precisely such a system into our home in Germany a few months ago, in anticipation of the birth of our son.

One of the things we were dead set against was using drinking quality tap water to flush the toilet when so many people around the world don't have clean water to drink! We didn't want our child growing up arrogantly flushing other children's futures down the drain.

Since here at the Solar CITIES European home office we like to practice what we preach and actually field test ideas on our own family before we go off to so called "developing countries" and "preach "it to others, we are slowly but surely working out the kinks on low-cost household level industrial ecology solutions that can be implemented by the residents themselves (though often with the recommended help of a certified local plumber or electrician for safety).

In the case of our greywater system the chief concern our friend Comert, the plumber who installed our solar hot water system, had was that fatty organic material from the kitchen sink and dishwasher would foul the greywater tank and clog up the toilet fill nozzle creating a maintenance nightmare. Furthermore, while the baby is young, we must often deal with filthy baby clothes that could contaminate the water to levels that would make irrigating the porch-top vegetables potentially unsanitary. We think the slow sand filter with its "schmutzdeck" that we are building to treat the greywater will help, but we wanted to have options.

The question became "how do we design a simple system that lets us choose which greywater to reuse and which to discard?"

The simple solution was the most obvious -- put in a T and valves. We ran all the pipes from the kitchen and the bathroom together and then, via one side of the T to an automatic pump located underneath the bathtub that pumps all the water to an elevated storage tank on the porch that feeds the toilet and the garden. The other side of the T goes to the sewer. In between are simple pool valves. Thus before the combined greywater pipes' output reaches the pump or the sewer drainpipe it has to pass through one or another valve. One permits the water to flow into the pump, the other allows the water to go down the drain.

(Photo shows the two "Kugelhahnen" -- PVC pool valves; one leading to the sewer drain, the other to an automatic pump that leads to a 600 liter plastic storage tank on the porch which feeds the garden and the toilet. The pump has a float valve and turns on automatically when full, then turns off again when there is no water to pump. It is the most expensive item in the setup, costing about 350 Euro. The 1 " valves were 14 Euro each. The author previously used a 50 dollar 12 volt water pump but had to turn it on and off each use and thought this would create a problem for the family that would discourage use)

When we want to use the greywater to fill our reserve tank we open the valve to the pump and close the one to the sewer. When we want to direct particularly problematic water to the sewer we turn the valves the other way.

Of course the simplest solution would have been to use a single three-way valve so that you only have to turn one handle, but such valves were not available in our local market and would have had to have been special ordered. Since Solar CITIES is about using locally found and recycled materials that ANYBODY can get off the shelf to improve the inflation resistance of our dwellings, we went with the valves available at the corner pool and garden supply shop just up the street.

Further improvements to the system would be to use some kind of solenoid instead of manual valves so that one could press a button to determine which way to direct the water, but the author doesn't have the time right now to explore that option.

For now we are happy to simply open the tile on the bathtub wall (we installed it with magnets so it is easy to remove and replace -- you can't tell it is a hatch if you didn't know it) and turn the valves. It's not a hassle because it is very rarely that we introduce water into the drain that could create a problem. 95% of the time we simply leave the valve to the greywater tank pump open and the sewer closed. This is because the way we have designed the system the water coming from the porch tank comes from a filtered output near but not at the bottom. Heavy materials fall to the very bottom of the tank and can be removed with a pool vacuum; fats, oil and grease float and so they don't get into the outflow either. Instead, we installed an overflow drain pipe 3/4 of the way up the tank that is connected to the sewer -- this way the greywater tank can never overflow, and when it does get full all the material that has floated to the top flows into the drain and is thus "skimmed" off of the surface of the water. This makes the tank self-cleaning with regard to lipids and other floating material.

The result is a tremendous savings in energy and water, and the knowledge that we never have to worry that we are pouring the future down the drain.

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