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Old 19-11-2006, 05:12   #1
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Water Purification

Here's one you don't hear every day:

Instead of the traditional way of using a high tech gadget (a watermaker) to top off water tanks, I am going low tech to save money and have a more reliable system in the long term, given that I may not want to be reliant on shore. Yes, I'm always doing something weird, right??

So what I'm doing is using a tarp to collect rainwater, as many people do in developing nations and here in the States as an environmental technique to get household water.

Problem is - I can't find information on water purification. They sell all kinds of junk in the marine store for purifying water. Stuff to make it taste "fresh" and other stuff from the UK that contains Sodium Dichoroisocyanurate, which is supposed to eliminate Cholera, Salmonella and stuff like that. There are millions of things on the market and I'm not sure which one works, or which one is appropriate.

I have read that you can't just drink straight rainwater for various reasons and you must treat it somehow. Problem is, every place I've read falls short of addressing the treatment issue.

We currently drink municipal tap water (which is what we fill our tanks with at docks) through a Culligan carbon water filter that is capable of removing giardia (I think that makes it a 1 micron filter). It also removes lead, asbestos, chlorine, all minerals, etc...

Only thing I can't figure out is:

1) What is wrong with rainwater that it isn't drinkable?

2) What must be done to correct this problem with raw rainwater?

3) If treatment with something like the chemical from the UK is the right way to go, what are the health effects of drinking that chemical every day for your whole life?

Any ideas? Any scientists or biology folks or rainwater harvesting folks on here? Help?
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Old 19-11-2006, 05:42   #2
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Home Water Treatment Devices
http://www.nsf.org/consumer/drinking...ogram=WaterTre
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Old 19-11-2006, 05:54   #3
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You can drink collect and drink rainwater and don't have to treat it if it collected using clean and sterile techniques:

http://www.newton.dep.anl.gov/askasc...0/wea00044.htm

The problem of course is that a collection tarp and tubing can become contaminated. However, I suspect no more contaminated than the delivery system of tap water.

Collect some and have it tested!

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Old 19-11-2006, 06:44   #4
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The main contamination risks come from animals or birds leaving droppings on the collector (tarp); although pathogens (including faecal coliforms, bacterial pathogens, and protazoan cysts such as Cryptosporidium and Giardia*) may be present in rainwater, and in urban areas there is an additional risk of chemical contamination (including metals like zinc, copper and lead) and other compounds.

*Sean is correct - these cysts are usually filtred at 1 micron absolute. The absolute 1 micron filter will more consistently remove cysts than will a “nominal” filter. Some nominal 1 micron filters will allow 20% to 30% of 1 micron particles to pass through. Look for the NSF trademark plus the words "cyst reduction" or "cyst removal" on the product label information.
Goto: www.nsf.org/certified/DWTU/

Another alternative is the use of a floating filter inside the tank connected to a flexible water line. This approach withdraws the water from approximately one foot below the surface which is considered to be the most clear water in any body of water.

I also recommend a Collector Screen over the catchment and at the top of the down-pipe is useful to screen out many of the contaminants before they enter the tank; and a Flush Diverter to reject the first wash of water over the tarp, to clean away debris and contaminants.
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Old 19-11-2006, 07:06   #5
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Sean you can drink the rainwater anywhere in the world. Like Gord said, it's your collection system that has to be clean, (sterile is impossible even in a hospital). If you take the prudent precautions of setting up just before it is ready to rain and then let the 'first flush' or basically the initial minute or so of good hard rain to be diverted, it will 'wash' most of the harmful materials (including most of the salt) away with it if you have any. In places where it may only rain for a few minutes at a time, collect it all in a seperate container (should be easy unless you have a huge collection system) and then treat that seperately before adding it to your water tanks.

The easiest treatment is the tablets. time is not a issue so that may be the way to go. The best treatment is one of the portable hand pump filters for backpacking, but it would take a long time for you to get the volume you need processed. (that and your arms would be REALLY sore). the only drawbacks to tablets are they can take 12-48 hours (depending on the type of tablet and quality of water) and they tend to leave a strong chlorine or chemical after taste and maybe a color again depending on the tablet. But it is drinkable.

The truth of the matter is that rainwater is probably better for you than most of the water you drink with the minor exception that it doesn't contain all the minerals that ground water does. So unless your going to drink rainwater exclusively for the next 6 years the minerals aren't an issue. Water treatment plants take the raw water from whatever stream, creek or lake is used as a reservior and processed physcially to allow the suspended sediment to fall out and chemically to kill bacteria and retard it from growing in the future. It doesn't do a whole lot else. If they try to, they generally wind up with a bunch of nasty chemical by products that make the water taste bad or are harmful (isn't EPA regulation fun).

If most people knew what the inside of the water mains that fed thier house looked like, they would probably drink bottled water for the rest of thier lives. (I'm a civil engineer, I know because I replace and install water mains.) You body is designed to take a lot of variation in it's quality of intake (within reason). People have been drinking rain water since the beginning of time and it was usually regarded as a 'gift from the gods' since it was the only water that could be counted on not to be 'bad', that or beer !

If you keep your collection equipment clean, and let the first flush pass, the only other thing I would do is taste test the water before you either divert it directly to the water tanks or add it after treatment. That is afterall the ultimate use and test.

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Old 19-11-2006, 12:11   #6
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I have been collecting rainwater on board with never a second thought as to it purity/suitability for drinking.
My lack of concern with this is probably due to the fact that nearly every farm house and rural property in NZ uses the roof as a catchment and feeds it into a (usually 5000 gallon) concrete tank for domestic supply. Once in a while we would clean the roof and gutters and fish the odd dead bird out of the tank, and we're all still alive and healthy.
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Old 19-11-2006, 13:22   #7
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Thanks for the input, everyone. I did read about rainwater catchment systems being very common in NZ and AU rural areas, and even in Sydney. I wondered if there was something I was missing, since everything I read in the States says I can't drink it, while so many others drink it their entire lives.

I suppose it's really the airborne pollution that could mess things up - solids, particles, chemicals, etc...

I highly doubt my tarp and downspout (temporarily rigged up for rain then taken down) would get contaminiated from birds or anything. It's more the chemicals I think that might be the issue in the North East USA, where all the air from the western part of the country comes after passing over all of the USA (generally speaking).

I think I'll give this a shot as soon as we leave New Jersey. I'm afraid to even breathe around here! ha ha ha
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Old 19-11-2006, 13:25   #8
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Hi Sean,
We've a place in Tuscany with our elder son and it's not connected to the main supply. So we are used to well water in the wet winter - and collecting rainwater into tanks whenever the opportunity arises.
I'd agree with all the others and say provided the collector surface is clean you'd have no issues on healthy drinking.....I would not worry also about any lack of minerals. We've had pals who exist off watermaker water for months and they get more than enough minerals out of their food product.
And also as another has said - we once filled a new pool from tapwater and I simply could not believe the colour - when bulked up it had a worrying yellow colour not unlike most of the water I personally produce! In that case it was only the chemicals added to the pool that made it come clear. A worry.
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Old 19-11-2006, 14:39   #9
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Thanks, John! Good input as well. I suppose I have only to worry about possible pollution related contamination. Tuscanny, NZ, etc... all beautiful places with fresh air. I suppose as long as I'm away from the NY/NJ area, maybe my air will be clean enough to leave the worry about airborne chemicals behind?

It's really those that are the most concern, not bacteria, since the catchment system is not permanent.
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Old 19-11-2006, 15:07   #10
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Sean, as you may have noticed life existed before water sterilization and most animals still thrive without it.<G> Many cruising authors have written in favor of using the sails to collect water offshore--after letting some heavy rain desalt them and wash off whatever is on them. Its been done.

But fecal contamination from birds, and whatever can get into your tanks and grow there, and the way water-born problems can literally knock you off your feet for a week, could be problems sailing.

The micron filters work, as long as you're willing to buy filters. All the fancy chemical solutions turn out to be some kind of chlorine or iodine, and you can get both of those direct as chemicals for way less. Not very tasty but a charcoal final filter will help with that. I'm also told one of the "flavor fixers" used with iodine is simply to add some vitamin c or citric acid IIRC.

But I think the most interesting option out there is UV-C. A UV-C light will destroy DNA, so installing one in your water line will sterilize eveything that passes it--without needing any chemicals or requiring you to drink them. There are some small ones sold for campers and larger ones sold for home water systems. If you split off your main tank from a "day tank" and made a point to sterilize the water while transferring it into the day tank, you'd only need to power the UV light during the transfer, i.e. once every day or two, and that could be done during charging, etc.
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Old 19-11-2006, 16:03   #11
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Rain water catcher

We used both RO and rain water catcher. Before we pumped anything into the tanks it went through a activated charcol filter, then into the tanks.

The second issue is if you are counting on rain as a primary source of wat er. It has to rain!. In our first year out we saw very little rain. Espeically since we were hanging around some arid desert islands in the Caribe. We barely saw enough rain to rinse the boat much less collect water.. just something to think about.
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Old 19-11-2006, 17:16   #12
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Hi Capt Bil,

So for clarity, you sent rainwater through a normal activated charcoal filter, and then into your drinking/house water tanks? This was along my lines of thinking at first, but then I figured I could use rainwater directly in my tanks, and try to purify it to a higher degree for drinking through some kind of inline filter, using the rest for household tasks like dishwashing.

By the way... I do recall seeing you in a very arid area of the Western Caribbean. In one month, there was only one good downpour there. Incidentally, I think that is enough water for my wife and I for a month's time.

My plan is to use rainwater as often as possible, but to of course fill up at the dock if we run short. We can go a month on full tanks, so it's not terribly inconvenient to jug water or to fill up with water at a fuel dock if we have a very dry spell.

I just see the rainwater catchment system as a way to get free water without heading to civilization, or having to deal with the installation, cost and maintenance of a watermaker.
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Old 19-11-2006, 18:26   #13
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Sean,
We're installing rainwater cisterns at our farm in Central Texas. It is a common practice here because of problems with groundwater contamination and the shortage of rural water supplies. When we had our shallow well tested the State chemist told me that filtering is essentailly the same for both rainwater and groundwater (and you get less oil in rainwater). Here is a link provided by the city of Austin that may give you some ideas:

http://www.austinenergy.com/Energy%2...Harvesting.htm
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Old 19-11-2006, 18:44   #14
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Here on the Big Island I've been living on catchment water for 15 plus years. I use a micron filter. Our collector is the roof of our house. Water goes in the gutters and then into downspouts and a 4" pipe to our 11,000 gallon tank. From there it is pumped via an electric pump through a filter and into the house. Every so often I put about two cups of bleach into the big tank (maybe once a year if I think of it). The tank is covered with a fabric covering made of shadehouse cloth.

It works well. Never an illness attributed to the water in our home. There are about 35,000 homes on the island that use the same system.

Isn't it amazing how people are rediscovering the "old" ways.

Good luck on your system.

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Old 20-11-2006, 03:42   #15
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Quote:
Originally Posted by ssullivan
Hi Capt Bil,
So for clarity, you sent rainwater through a normal activated charcoal filter, and then into your drinking/house water tanks? This was along my lines of thinking at first, but then I figured I could use rainwater directly in my tanks, and try to purify it to a higher degree for drinking through some kind of inline filter, using the rest for household tasks like dishwashing.
You want to ensure that the water going into your tankage is as axenic as practicable; hence the advice to screen and pre-rinse your catchment tarp & down-pipe.
For the same reason, filtration should occur at POE(point of entry) .

Activated Carbon filtration is most effective in reducing certain organic compounds & chlorine from source water, and improving aesthetically objectionable water (colour, taste, & odour). AC filtration may be performed at POU (point of use).

AC filtration does not remove microbes*, which are most effectively filtred with a 1 micron (absolute) filtre.

* There are some expensive Solid Block AC Filtres rated for microbial rejection (as low as 0.5 micron).

Household tasks, such as dishwashing, bathing & kitchen cleaning, should be virtually as clean as your potable water (ie: there’s not much point in pouring unadultered water into a contaminated glass).

From Pure Vida’s “Rainwater Harvesting” link:
”... The best strategy is to filter and screen out the contaminants before they enter the cistern ...”

BTW:
Rule of Thumb:
You can expect to catch about 100 Gallons of rainwater, per Inch of Rainfall, for each 100 square feet of catchment tarp.

US Weather - Average temperatures and rainfall in US cities:
http://countrystudies.us/united-states/weather/
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