Archive for June, 2009

Using rainwater Indoors

June 9, 2009

With more rainfall, people are thinking more about use of rainwater indoors. With a more steady supply, use of rainwater indoors for non-potable (i.e. non-drinkable) uses becomes more interesting. In January, the State of Georgia amended their plumbing codes to include the use of rainwater in homes for some non-potable uses.
Non-potable indoor uses include primarily toilet flushing and laundering in homes. This development follows other states and regions around the world that use collected rainwater for both potable and non-potable uses.
So how much can city water use be reduced by using collected rainwater? According to the EPA, a typical family of 4 uses about 25,000 gallons per year for toilet flushing and about another 25,000 gallons for laundry. This 50,000 gallon non–potable usage makes up around half of all indoor water use, so the water savings can be substantial.
It is actually quite straightforward to set up a rainwater system for non-potable indoor uses. The Georgia code requires that collected rainwater goes through a filtration stage followed by disinfection. Filtration can be accomplished using a 3-5 micron equivalent filter and carbon filtration is desired for further protection to assure no odors. The most typical disinfection method is to use UV treatment. Many reliable systems are available to do this. If the system is sized to last at least 3 weeks and if low flow toilets are used, our family of four would require about a 500 gallon tank and still have some left over for outdoor watering. All systems must have a city water back up which would automatically take over if necessary as well as a bypass.
The Georgia Code is quite conservative in that the water produced by a well designed system installed to code could actually produce potable or drinkable water. The main difference between potable and non-potable in this case is merely that for the water to be designated potable requires that periodic testing for coliforms be done. The process for water treatment of rainwater for potable water applications in other states is exactly the same as the one described in the Georgia Code. The good news in this is that if the code is updated to allow use of rainwater for potable water applications, systems already existing for non-potable applications may already be in compliance!


So, what if the drought is over?

June 7, 2009

Well, we’ve had 3 straight months of above average rainfall. If June is also above normal, the drought will be declared over and the watering ban may be lifted. But, we are now moving into the drier months and it is possible we will remain under watering restrictions. Even so, one may wonder what normal Atlanta rainfall conditions mean with regard to the benefits of a rainwater collection system. Rainwater collection systems in the form of multi-thousand gallon tanks and cisterns are popping up all over metro Atlanta in response to the lower than average rainfall and low Lake Lanier levels the last 3 years. Are these systems still a good investment if there are no watering restrictions and rainfall is normal? The answer is yes. In fact, some of the reasons for having a rainwater collection system for your home actually become more important when it rains more. Consider that:
1. With no watering ban, we can once again water turf and gardens with our automatic irrigation systems. Feeding these systems with city water can cost hundreds of dollars per month. Feeding your irrigation with rainwater is nearly free and will definitely save you money.
2. Even under normal rainfall conditions, we will likely experience several periods of more than 10 days without appreciable rain this summer. A rainwater collection system bridges across these periods to keep your lawn and garden lush and vibrant. Even though rain itself nourishes our lawns and gardens, we will still need to water to keep plants at their optimal best.
3. When it rains a lot, rainwater collection systems prevent heavy erosion and storm water runoff problems. By collecting water and using it later, soils can better soak up water and replenish the ground water supply. For those who think drilling a well is the answer, keep in mind that irrigating with well water has a net negative effect on ground water supply.
4. The possibility of using rainwater year around for indoor non-potable uses such as laundering and toilet flushing becomes much more attractive the more it rains. With additional filtration and UV disinfection, the Georgia Plumbing Code allows use of rainwater indoors for non-potable uses. The typical family of four uses around 50,000 gallons per year for these uses, so the cost savings and other benefits can be substantial.
And whether there’s a drought or not, collecting rainwater is a smart choice to help alleviate Atlanta’s ongoing water supply challenges. This may be as good a time as ever to consider rainwater collection to protect your landscape investment use less city water.

June 3, 2009

A few weeks ago, I was in Washington and met with some people at the EPA and contractor firms to talk about rainwater collection, water supply challenges, and trends in regulation, legislation, and long term solutions.  It was really fascinating and I am fired up to really make a difference, not just in the Atlanta area but everywhere.  One topic that came up a lot was the idea that water resources are much like energy resources and are really connected in many ways.  For this first blog post I want to throw out some ideas and see what viewpoint all of you out there have.  I especially am interested in one question and want to know if anyone has data to back up a hypothesis I have.

One idea that’s floating around in energy distribution is the concept of the smart grid and decentralized power supply.  In short, some studies have been done to show that it may be more cost effective and efficient to augment existing central power plants with residential solar, wind power generation.  In fact, it may be possible to avoid investment in new power plants if enough adopt alternative, decentralized sources of electricity.  So much so that municipalities may consider financing residential installations in lieu of huge long term projects.  The benefits we talked about are:

  • Spending is gradual over time rather than having huge government outlays for infrastructure projects.
  • Decentralized power supplies do not have interruptions as much due to storms or heaven forbid terrorist attack (point brought up by someone with connections in DHS)
  • The decentralized technologies are obviously more sustainable.

So, we thought why could this model not work for managing the water supply and wastewater treatment?  Rainwater collection and graywater recycling are clearly decentralized approaches to water supply.  What would be the effect on Atlanta’s water supply and water treatment infrastructure requirements if more residences and businesses had rainwater collection or graywater recycling?  What percentage of homes and business in metro Atlanta would have to have rainwater collection in order to make the planned reservoirs to be unnecessary and eliminate perennially empty Lake Lanier?

Here’s my big question that I would like to hear some debate and receive some information.  What would be the net cost of having residences and businesses install rainwater collection or graywater recycling versus the cost of implementing the greater Atlanta water plan?  If the cost of the former is less, would government funds be better spent financing rainwater collection versus financing large, arguably less environmentally friendly infrastructure projects?  The types of costs that would need to be considered in such a comparison are:

  • Costs for water treatment
  • Costs of erosion and stormwater management
  • Cost for reservoir projects
  • Energy cost of centralized water management compared to decentralized
  • Costs to protect ourselves from someone messing with our water – contaminating it in some bad way.  This may sound alarmist, but I met someone who is studying just that possibility with the Department of Homeland Security

As you may guess, I have a particular position and interest in this topic, but I really want to find data and studies to answer these questions one way or another.  If this means initiating grants for research to find out more specifically how this would work out, I’d be interested in doing that too.  I do not claim to have answers and really am striving to be better informed on these topics.  My gut feel tells me something, but the scientist in me wants data to support that feeling.