-It CAN BE one of the purest sources of water possible (this depends on how we handle the water)
-I don't require large volumes of water and I mind my consumption
-My garden will be planted with appropriate crops for my area, and when I do water, I use a hose to water the plant, not a sprinkler
-I don't have a bath, and my shower head is a low-flow (around 1.5 gpm)
-I hand wash dishes
-My clothes washer is a water/energy efficient apartment model
-I use a composting toilet
-It is cheaper than drilling a well, and way easier and safer that digging one
In short, the rainwater collection system has exceeded my expectations. It's been low-maintenance, problem-free, and generally pleasant to use. In the first month, I was nervous about the water level, but thankfully in March we had a one major rainstorm which nearly filled the tank in one day. Since then, the tank has never been less than 3/4 full.
The tank is a black poly cistern from Agrisupply, in Garner, NC. Not only was the 1150 gallon tank a great price (around $550), they had everything I needed including the first-flush diverter, a parts list, even a video on how to setup the cistern!
One of the greatest resources I discovered was the Texas Rainwater Harvesting Manual. This publication is awesome, and it gives a good idea of the dos and don'ts associated with harvesting, and they cover touchy subjects, like using chlorine to shock the tanks and indoor uses of rainwater.They give an informative overview of different types of systems, specifics on roof surface area for catchment , and comparisons of commercially available components.
When figuring how much water I would harvest and what I'd need, I used the 1.6 Sq ft of flat roof area will yield 1 gallon in a 1" rain formula. So with my roof, I've got about 576 square feet, porch roof included.
576/1.6=360
3" PVC pipe holds .36 gallons per foot, so each of my 9' diverter sections hold about 3 gallons of waste water, and they continue to 'leak' during the shower. So, In a rainstorm that produces about 1" of rain, I can expect to harvest around 300-350 gallons.
Although rainstorms where we get an inch of rain or more are rare here, we do get many storms with 1/2" to 3/4" in short time periods, and this is perfect for collection. With the first-flush diverters, a strong rain is required to float the ball and collect clean water. 
There are loads of big expensive reverse osmosis filtration systems on the market, but I chose to take a simpler approach. Most importantly, I have the first-flush diverters, which prevents light rains, dust and junk from ending up in my tanks. Second, at the opening to my cistern, I use a stainless colander covered in a 5 mil strainer bag. In my indoor untilty closet, I have a high volume sediment filter. The water for washing clothes, dishes and showering comes from there, and isn't filtered further. For drinking water, I use a sink mounted carbon filter.The only chemical treatment I use is a small amount of 35% food grade hydrogen peroxide directly in the cistern following a big rain, about once every quarter. This shocks the tank, and should discourage any growth in the tank. I'd like to thank my friends at Geopathfinder for introducing me to using H2O2 in the tanks. Their site is the only resource I could find with any information regarding the correct amount to use at which frequency. The amount they recommend is about 3/4 cup H2O2 per 1000 gallons (2 cups in 2500 gallons), but add too much and the pump will cavitate (suck air). I've heard of chlorine and other chemicals used to shock the tanks, but I don't want that stuff in my drinking water. Chlorine is a nasty chemical, and municipal water supplies have been using H2O2 for some time. At least Hydrogen peroxide will quickly decompose into water and oxygen gas.
Most of the water for outside chores comes from the overflow tank/ 275 gallon IBC tote. I've got a garden hose hooked to the outlet valve, and the water is gravity fed. These tanks are awesome, but it's hard to know what has been stored in them, so I wouldn't use them for drinking water.
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| Homemade manifold with add-on |
The rainwater system would run me almost $1000 and would include 2 first-flush diverters, one for each gutter, an 1150 gallon cistern, and an IBC tote 275 gallon overflow tank. Inside my utility closet, I have a 24V Shurflo 2088 diaphragm pump, inline prefilter, pressure tank, on-demand propane water heater, sediment filter, distribution manifold and exhaust fan.
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| HW heater, exhaust fan, sediment filter |
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| Pressure tank with pump mounted on top |
