On Another Note: Rain Water Collection Systems

I know this is supposed to be about data center and network virtualization but I'm going to take a brief break on one posting to discuss rain water collection. The main reason is because I couldn't find much information out there for cost analysis and return on investment potential and I'm sure others could benefit from some real data.

To set the stage, I live in the Raleigh, NC area and I have a ten zone irrigation system for my lawn. The water bills rise from an average of $45 per month to an average of about $200 per month during the summer months when I'm having to irrigate two to three times per week. Because of the amount of money we're talking about, I decided to look into rain water collection systems that could be tied into my irrigation and help offset the water costs each month.

After investigating lots of options, I called up a local company called FreeFlo Water Recycling Systems. They had a system that included underground storage tanks, filtration systems, pumps that could generate about 24 gallons per minute, and optional tie-ins to my home water to service toilets, the dishwasher and the washing machine. It sounded great from the beginning and when they came to discuss my needs, they were very knowledgeable and had lots of ideas for what I would need. They left with all the information and said I would be getting a quote in a couple of days.

The day following that, I had my landscaping guy come over to discuss a couple of other projects I was planning. I shared with him what I was looking into and he asked me some questions about the system. When I told him that we were upgrading the basic package and installing two 1700 gallon tanks, he asked if I had an idea about how much water we used with each irrigation cycle. I had no idea so we worked a few minutes on some numbers to figure it out. With my ten zones and the various types of heads, we calculated roughly between 2200 and 2500 gallons of water each time I irrigated. The wheels started to turn.

The next step was to figure out how much I could possibly save in a given year. The guy from FreeFlo suggested I could cut down my water bill from about $200 during the summer months to about $35-$40 per month. He said he had some customers that had cut their bills from over $300 per month to less than $50 per month.

I started out by figuring how much collection surface I would have. I figured I probably have a good 2000 square feet of roof and I added another 1000 square feet in for the driveway water and any other misc. water I was able to collect. This gave me a total of 3000 square feet of collection surface and I really think this is a best case scenario. For every 1000 square feet of collection surface, you can capture about 600 gallons of water for every 1" of rain. Given that NC averages 42 inches of rain per year, that gives me a maximum amount of rain water I could collect of 75,600 gallons per year.

It's important to understand a little about how the system works. I would have two 1700 gallon tanks giving me a total of 3400 total gallons I could store. Basically if you got a couple inches of rain over the course of a few days, you would fill those tanks up and then you would lose the rest to overflow. In order for me to actually collect the best case scenario of 75,600 gallons per year, the rain would have to be evenly spaced out between my irrigation cycles so that I didn't lose any to overflow and the rain would all need to come during the months that I have the irrigation system running. Obviously this is almost impossible and would most likely never happen but that's what would have to happen for me to be able to capture that 75,600 gallons each year and effectively use the water. It's also important to note that at full capacity of 3400 gallons, I don't have enough water to get through two complete irrigation cycles without having city water kick in.

For the purpose of this exercise, let's assume that I am able to capture the full capacity of 75,600 gallons and I'm able to use it. This would save me $558 per year based on my water rates and this really is a best case scenario.

The quote came in for the entire system and they want $11,200 for a turn key installation. The return on investment is over 20 years and this is assuming no further money is put into the system for maintenance during that 20 year period. It's true that water costs could go up but over time my watering needs should also go down due to my lawn becoming more established. At this point, I think I'll look for something with a much quicker ROI. On to solar power.......