The Demo Site

The following questions just came in from Rachel, a colleague in the green-building industry. My responses are in bold after each question.

We are hoping to incorporate a rainwater harvesting system for indoor application (we would use it for outdoor application as well but I imagine that the local rainfall in New Orleans – averages 5-6 inches/month – would provide more than enough irrigation – ?)

If you choose plants wisely and grade your site effectively, you might need very little supplemental irrigation in a place with so much humidity, but you must also be prepared for dry times when many plants need more water than they are getting from the sky, and you should also expect to irrigate newly installed plant material during the time it takes for root systems to establish themselves.

o Do you typically use roof gutters to channel the water into the cistern?  Is this an efficient way to catch water?  What type of roof works best for this (butterfly, shed, etc.)?

Simple pitched roofs that pour into gutters are best shaped roots for water harvesting in cisterns. Weather-coated metals that allow for clean and rapid delivery to the conveyance system are also desirable.

o Where do you usually place the cistern, and can it be placed underground?

Unless your project is in one of the higher parts of New Orleans, I would advise against an underground tank on the basis of the high water-table there. It’s also MUCH cheaper to install an aboveground tank than an underground one, and since it does not freeze there, you could get away with it. (Here at 7,000’ ft., we usually have to partially bury or fully bury our cisterns, but I have a client here who has [after a decade] never had a problem with his aboveground tank! But I have also had clients who do not attempt to collect any water in their aboveground cisterns until about this time of year.)

o If it were to be placed beneath the ground surface, would it be problematic/require substantial energy to get the recycled water back into the house, if the house is raised 8’ above the ground? Would this be problematic even if the cistern were above ground?

I would consider putting your cistern under the house since it will be raised 8’ from grade.

· We are also planning on using a greywater reuse system from the washer, shower and sinks.

o Where would a greywater system typically be installed?

The best use of greywater is directly on the landscape, and this could be one way to avoid the supplemental irrigation (from a surface or groundwater source) that I referred to in my first answer. BUT it may not be legal in that part of the world, so check with local authorities before pursuing greywater there. During times when the landscape is saturated, at the very least you would want to be able to conveniently divert greywater back to the regular sewage system for the house.

o Does it require a substantial amount of maintenance?

No. If you follow the advice in my upcoming book, Harvest the Rain, greywater requires little maintenance. My favorite resource on the subject is www.oasis.design.net

· We are hoping to comprehensively address surface water runoff.

o If we design the site so that 100% of the lot (excluding area under the roof and cisterns, etc), implementing vegetation and permeable paving, do we need to incorporate a drainage system beneath the ground and, if so, how does that work exactly?  Have you done something like this before?

Sorry, that’s out of my high-county bailiwick.

o Is this an extremely costly measure?

Cisterns are typically not cheap. In addition to the material and installation costs of the tanks themselves, you have to convey the water to the cistern, prefilter the water while it is being conveyed before it gets to the tank, pump the water, pressurize the water, filter it again before it can be used indoors, and you have to provide for ventilation of the tank so that the pump functions efficiently while also making sure that the tank has a properly sized overflow pipe and a daylight point for the excess water. Don’t forget to figure in other bells and whistles, such as a float switch to turn off the system when the tank is dry, a make-up water system (from a well or water utility) during times of drought, and a level indicator. The last item can be as inexpensive as a long dipstick, while the make-up water system can drive up the cost quickly, especially if your water source is far away. Did I mention the various micron filters and ultraviolet light tubes that you will need to burn out the nasties that you might pick up from things like bird poop on a roof? This adds to the cost of water used in the house (although it may not be necessary if the only uses are to be, say, flushing toilets and/or doing laundry at hot temperatures).

· Do you have any other advice or insights in the range of water recycling/filtration, including cisterns, rain gardens, permeable pavement, etc.?  Specifically systems that can be installed cheaply, are easy to maintain and are highly effective?  Am I asking for the impossible!?

It’s great to hear from you, Rachel! Nothing is impossible! If your clients need financing for their water harvesting system, they should check with the Permaculture Credit Union, www.pcuonline.com . Unlike the presidents of other financial institutions, the CEO of the PCU’s eyes will not glaze over when you utter words like “overflow pipe,” “greywater valve,” and “rain garden.” I say go for it! I imagine that your clients will have the cleanest and healthiest water in the neighborhood by the time you are done!

Thank you!!

Thanks for asking!! And good luck with your project, Please keep us posted!