Roof water harvesting and emergency water supply

Just a thought about catching rain water to use in an emergency (I have to have a rant once in a while). . . .

It could easily happen. An emergency situation due to an earthquake, a power outage, or the “100 year floods” that have been happening every 10 years or so. What would you do if you had no dependable water for, say; 4 weeks? Rush to the store and buy bottled water – like several hundred thousand others? How long before its gone?  Water is critical to survival, but its always there when you turn on your faucet. . .    .  If there is an extended power outage, or there has been an earthquake there will likely be no water available for a VERY LONG TIME (speaking of quakes, we just had one off the coast of Oregon yesterday April 11 – a 5.9; and one today April 12 in the Gulf of California a 6.2 ). If there has been massive flooding and all the water is contaminated, everyone else will be looking for water – 4 days without water and your in very big danger of meeting your maker; think about it, and children really need water – what do you do? Drink from a mud puddle? Drink flood water? Can you even imagine what would be in that water? Of course these two options are crazy. Now; that slow sand filtered roofwater starts looking really good, doesn’t it? – even if there are a few coliforms in it, and you’re going to be really really careful about it; right? You’re going to make sure the filter is taken care of, right?  My point here is that each person is responsible for the operation of their roofwater filter and each person makes their own decision about how to use it – but it should be an informed decision based on knowledge. Each person makes their own decisions about what to do – I am not responsible for others actions or decisions  and all of the information I provide still does not make water 100 percent safe, but in an emergency this 55 gallon barrel of filtered roof water sitting by my garage is going to look really, really good. Think carefully. Several months without water supplied to your suburban house will be a horrific situation for you. As long as it rains, you will have water – if you have set up a slow sand filter; that is.

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2 Responses to Roof water harvesting and emergency water supply

  1. Brian Byrne says:

    First off I would like to congratulate you on your easy to understand system and presentation on your video I am in the process of constructing a system similar to your own design. To be used for collecting rain water for use for showers and washing cloths and dishwasher toilets and maybe for potable use. I am living in Ireland so rain is not a problem as we say here it only rains in between the showers.
    I have designed an automated system that will work as follows. Filtered rain water from slate roof into storage tanks I will be storing 300 gal to start off. From there it will run into sand filter and from the filter to a storage tank that has a ball valve installed in it. From that thank it will be pumped to the tanks in the loft to feed showers and utility’s.
    Now from drawings I have seen there is normally an inch or two of water left covering sand filter at all times. I plan to feed water into the filter by use of a ball valve onto a dispersion plate I have designed so it does not disturb the sand. So when the storage tanks fill the ball valve will shut water from filter off and when filter fills the water to it will shut off but leave water still covering sand.
    The system will start running again when water is taken from the loft tanks.
    How long does a filter have to be in use from first start up to be effective? As there seems to be different times set depending on whom one asks. But you were the only one with proof of certification for your water so I reckon you’re the best one to ask.
    Have you ever considered filtering the water twice as I am thinking on it to see if what happens between first test on one filter and another on two filters?

  2. Orpheus says:

    Brian, thank you for taking the time to comment. I hope your rainwater harvesting system works well for you. It sounds like you have a very good start. You’re using, in my humble opinion, one of the best roof surfaces possible for rainwater collection.
    As for the “time to ripen” for the biolayer – to the best of my knowledge, it depends on temperature, and the amount and type of microbes in the water. Here, in north west Washington state, the weather is cool most of the time (between 3 and 10 degrees C) with the exception of July, August, and September when we often get temperatures of 30 degrees C or higher. The cooler the temp, the longer it takes to start up the biolayer. My experience has been anywhere from 4 weeks to 2 months, but its hard to start a rainwater filter here in the summer when the ripening would likely be much faster then winter spring or fall, because we get very little rain in the summer. I want the filters I use to be 99.999 percent efficient so I strive for 0 coliform per liter in the tests I have done; however, the pathogen removal, could actually start much earlier than 4 weeks – its just that the log reduction of pathogens in the output water just gets better with age. If you have a way to test for coliform, I would try a test at 3 weeks from start time. Be sure to test input and output at the same time.

    I do know from experience that these filters just get better with age. Filter 1 has not been “cleaned” for 4 and a half years now, the flow rate has stabilized and the water output is super-pure – I have used it in my deep-cycle batteries for 4 years and have had no problems at all; in fact, the batteries have lasted longer than they are supposed to – so that is some indication of how pure the output water is. I just read a new paper on biosand filters that states essentially, that the only reason to “clean” a biological sand filter is to keep a high flow rate. If a person is storing water, and has a big enough cistern, the flow rate is not that important, however if the filter is used as a main source of water directly from the filter, then regular “cleaning” is necessary to maintain a usable flow rate.

    Excellent idea – filtering the water twice – I have not tried it as an actual setup but I see no reason why it would not work. As long as there are some microbes in the water a biolayer will eventually form and become active. One could probably get away with using a very fine sand in the second filter, maybe something as fine as .15 mm effective size. I do something similar with the re-circulation but it might be better to run the water through a much finer sand in a second separate filter, and I have not tried that yet.

    We aren’t drinking the water from our filters, here – yet, however we have been using the water on our vegetable garden. A UV filter would be a necessary addition for using the water as potable, and even then the turbidity level must stay below 1. For all other uses the water is great.

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