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Rain water harvesting calculator

Discussion in 'General Survival and Preparedness' started by ColtCarbine, Mar 15, 2011.

  1. ColtCarbine

    ColtCarbine Monkey+++ Founding Member

    1. Find a rooftop anywhere in the world.

    Type in an address below and hit GO!, or, just use the map controls to zoom to a roof.

    Here is the link: http://www.save-the-rain.com/world-bank/

    This is in metric but can easily be converted to gallons.
    toydoc, Falcon15 and RightHand like this.
  2. ColtCarbine

    ColtCarbine Monkey+++ Founding Member

    My results are as follows:

    3. Results:

    You could grow...
    <table style="width: 100%;"> <tbody><tr> <td style="height: 12px;"> 274kg
    </td> <td style="height: 12px;"> 83kg
    </td> <td style="height: 12px;"> 103kg
    </td> <td style="height: 12px;"> 219kg
    </td> </tr> </tbody></table> [​IMG]

    The area of your roof is: 145.6 m²

    The amount of rain this area receives in a year is:1100mm

    You could harvest: 160160 litres!

    That's enough water to flush an average toilet: 26693 times!

    ETA: A toilet uses 6.0 liters (1.6 gals.) per flush if it is a new low flush toilet.

    If this calculator is correct and I did my conversions right. I can harvest 100,098.75 gals. that seems awful high to me.
  3. cool hand luke

    cool hand luke Monkey+

    Bad conversion there somewhere. 1 gallon us 3.8 liters so you should have about 40,000 gallons.

    HOWEVER this us of course the optimal condition and assumes you could capture all of the rain on your roof. We only have half the rain you get but typically get most of it in the spring. How much storage can you realistically have?
    ColtCarbine likes this.
  4. ColtCarbine

    ColtCarbine Monkey+++ Founding Member

    Thank you for pointing that out. I multiplied the numbers when I should have divided, my bad. [beer]

    Do I have the means to store 40,000 gals. of water, nope. However, this is the approximated amount that could be harvested from my roof over one years time.

    The point behind the posting was to show folks just how much water could be harvested from your roof alone. I would imagine most people do not realize just how much rain water does go down the storm sewer or is absorbed into the ground if they are not connected to a storm sewer.
  5. BTPost

    BTPost Old Fart Snow Monkey Moderator

    Since Rain Water collection is how I get my water for 9 months a year, this isa very interesting discussion in my view. I find I do very well with about 1000USG of Storage Capacity, and another 1200USG of collection capacity. I live near the North Pacific Coast and we get between 30 - 50 inches of rainfall a year, on average. Our biggest problem is building a Debris Trap to take the evergreen needles and other particlulates out of the collected water before it goes into the collection containers. One of my neighbors has designed a very good fixture that works well, and this summer I will go down and measure it up and make a Cadd Drawing of it, and post it for those who are interested.
  6. ColtCarbine

    ColtCarbine Monkey+++ Founding Member

    The correct calculations for the potential amount of rainwater that could be harvested from my roof is 42147.36842105263 gals.

    This translates into 115.47224224945927 gals. per day. Keep in mind this is an average and not the amount that could fall each day. That is more than enough water to keep my family alive without needing any other outside source of water. The summer months would be the problem though if a person could not store enough for the dry months.

    More than once I have posted on this forum that I do not worry about water. I imagine there were some that wanted to call BS but never said so. Hopefully, others will realize the same and see that it isn't BS. Not all hope is lost when it comes to drinkable water.

    However, if there was a nuclear, biological or chemical fallout in my area, the rainwater would be worthless.
  7. ColtCarbine

    ColtCarbine Monkey+++ Founding Member

    I'm interested, please do share. Rain water harvesting is on my to-do-list. I'm not sure why I have not done this already. Probably just laziness and the last thing I want to do is plumb on my own house, the pay isn't very good.
  8. ColtCarbine

    ColtCarbine Monkey+++ Founding Member

    BTPost no need to trouble yourself with a CAD drawing, I can read/interpret two dimensional drawings.
  9. BTPost

    BTPost Old Fart Snow Monkey Moderator

    Well actually this is NOT specifically true. Since fallout is significantly bigger in size that your average Bacterium, a good 1-5 micron Water Filter, will take care of the Nuclear particulates with ease. Same for Biological issues. Chemical issues can be dealt with by using an Activated Charcoal Filter. Viral contaminants can be dealt with by using a UV irradiation tank. I use a simple system that has all these systems incorporated. See attached picture....

    The filter on the left is a 2 Micron Filter. the one on the right is an Activated Charcoal Filter, and the Stainless Steel tank, above has an IR Radiation Lamp running thru the Axial Core.
    ColtCarbine, toydoc and Falcon15 like this.
  10. Falcon15

    Falcon15 Falco Peregrinus

    ColtCarbine likes this.
  11. cool hand luke

    cool hand luke Monkey+

    We only get about 20 inches of rain a year up in the top of texas, but you should be here the 2 days we get it!
  12. Falcon15

    Falcon15 Falco Peregrinus

    So much the better, CHL. Store what you can get so it doesn't just *poof* vanish!
  13. ColtCarbine

    ColtCarbine Monkey+++ Founding Member

    Great, here I thought I knew all there is to know about plumbing and you come along and kick me in the groin. See what I get for making a broad statement. I appreciate the insight and correcting me, you do realize that was hard to say. [bow]

    I knew that some filters would take care of some chemical and biological issues but did not realize this applied to radioactive particles. I guess it does make sense when you think about, I just never gave it much thought. I would imagine like any type of filter and depending on the amount of particulates you are filtering will determine how often they need to be changed. It would be a good idea for a person to have few extras on hand, being in your locale that is a given since the hardware store isn't just down the road.

    Do these filter most of the known chemicals and biological compounds in existence? I could look up this information but then this would not open discussion for others to learn from.

    Any and all information would be greatly appreciated from anybody in the know.

    Yeah, I have witnessed the flash flood type rains you guys get in Texas. That is a tough one I'll admit, not having any consistent rainfall. This could complicate things without a large storage tank.

    What is the average depth for aquafiers in your area?

    Any idea of the water quality of the aquafiers in your area. If push came to shove in a SHTF scenario, wells can be dug manually but it is time consuming that has many unknown obstacles which could lead to starting over. Besides that I'm guessing the ground there is not the friendliest to dig in or bore a hole into with a manual.

    Any nearby rivers, creeks, ponds or lake that water could be transported from and then filtered and/or boiled?

    Just bouncing around ideas as they come to me. Great, am I going to have to swallow more of my own words posted previously.
  14. cool hand luke

    cool hand luke Monkey+

    I'm getting REALLY familiar with our local aquifers with my new job. The one great thinga bout this region is it is sitting on the largest aquifer in the US. However, it's down about 100-300 feet around here. Luckily I know of a ton of wells that are drilled for monitoring. I'm working these into my bug out plans, including ways to get the water.
  15. ColtCarbine

    ColtCarbine Monkey+++ Founding Member

    100'-300' is not that bad, that is a normal depth for a well around here. I've heard of some as deep as 500'-600', just depends on where you are drilling. Good to here you have means of obtaining water.

    Check out this video on building a Bailer Bucket for obtaining water from a well. As long as people can revert back to technology of yesteryear, there is no reason that people can not still live somewhat of a reasonable lifestyle. It might not be what we are used to today but it's better than dying.

    The Hydromissions BB-01 "Bailer Bucket" is about as low-tech as you can get. It is basically the classic idea of lowering a bucket down a well, but modernized for smaller diameter (4 inch/100mm) tube wells. We sell the BB-01 as a simple kit that packs into an ultra-small (4 inch x 4 inch x 6 inch) box, weighing a mere 21 ounces. The real beauty of it is that, once in the field, all you need to buy is a short (3 ft/1 meter) piece of 3 inch diameter PVC and a rope. And if you want to get fancy with a crank and pulley system (windlass), we have designed an excellent one using any junker bicycle that you happen find lying around (see detailed instructions in the "Free Plans" section). This system can make a MAJOR difference in remote villages due to its simplicity, extremely low cost, and local sustainability. In addition, the BB-01 "Bailer Bucket" allows you to get water out of a well even when the water level is too little to get out with a pump (if you've ever sucked a well "dry", you know what we mean).

    <iframe title="YouTube video player" src="http://www.youtube.com/embed/PzD6k2OoQ5Y" allowfullscreen="" width="480" frameborder="0" height="390"></iframe>

    <iframe title="YouTube video player" src="http://www.youtube.com/embed/fUNCHdxBW_Q" allowfullscreen="" width="640" frameborder="0" height="390"></iframe>

    <iframe title="YouTube video player" src="http://www.youtube.com/embed/UYay9-2UMwM" allowfullscreen="" width="480" frameborder="0" height="390"></iframe>
  16. ColtCarbine

    ColtCarbine Monkey+++ Founding Member

  17. ColtCarbine

    ColtCarbine Monkey+++ Founding Member

    You just need a container to trap particulates.

    A catch basin upstream of the storage tanks would work for the heavier particulates, same thing that is used in parking lots for storm drainage. This could be something as simple as just adding a smaller tank than you have upstream with piping penetrations.

    A grease/oil interceptor would work on the heavy particulates and the evergreen needles. Keep in mind I'm not saying go buy a grease/oil interceptor because those bad boys are not cheap but a person could build one nonetheless.

    It is basically, a large steel box with baffles and the inlet/outlet penetrations are at the same elevation below the lid to create a water seal. Usually the inlet and outlet penetrations are about 6" below the lid. Obviously, you would not want to use a steel container for potable water use but the same could be accomplished with a plastic tank. I could forward or lead you in the direction of some technical data and cut sheets with dimensions for these. There is a bit more to these (especially on the piping/venting and flow control) but I tried to elaborate on the basics.
    BTPost likes this.
  18. ColtCarbine

    ColtCarbine Monkey+++ Founding Member

    BTPost for those piping penetrations into a plastic tank you could use a bulk head fitting, for a water tight seal to the tank. Maybe you already knew this but thought I'd mention it just in case.

    Link for installation instructions works.

    Here's an example of one made from PVC:


    4" Bulkhead Fitting - Loose

    Click here for Easy Installation Instructions.

    Part Number: FA0400PO

    Size: 4"D
    Weight: 3 lbs.
    Ships From: NY
    Freight Calculator
    Online Price: $62.39

    <input name="ImageButton1" id="ImageButton1" src="http://www.tank-depot.com/images/addtocart.jpg" alt="" type="image" border="0">
  19. chelloveck

    chelloveck Diabolus Causidicus

    One way of working out the harvesting potential of your roof / hard standing is to calculate the area in square metres, and the average rainfall per month from local rainfall stats in millilitres. 1 millilitre of rainfall x 1square metre of area = 1 litre of harvested water.

    A simple rain guage can be used to help you to estimate what your approximate harvested water should be subsequent to a downpour. Calculations should be considered approximate as harvesting may be somewhat less efficient with steeply sloping roofs, and losses due to first flow foul water diversion , and losses due to leaking gutters / piping.

    Structures with iron roofs, in some areas may also harvest dew / condensation in some favourable micro climates that could supplement rainfall.
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