In thinking about a longterm survival situation, I realize that no matter how much water I store, the supply can run out. When the supply runs out, finding a source of clean water may not be possible. If I hunker down at the house, I may need to take some water of which the quality is unknown, and use it.

So, I have been thinking about a system that I could build that would provide a good supply of clean water. In my thinking, I would probably want to work in stages.

My first stage would be a tank with two outlets, one at the very bottom and another some distance off the bottom. Put water into this tank, let sediment, etc. settle out of it and.or rise to the top, and draw water off from somewhere in the middle.

My second stage would be to try and filter it through sand. Slow sand filters are used in third-world countries to supply clean water. But, I really have no idea about using one of the filters that relies on biological growth near the top to clean water. I would probably build a couple boxes, fill them with sand, and use one at a time to seep the water through.

My next ideas would be to filter it again, possibly through carbon. I know activated carbon can remove a lot of chemical impurities, but sooner or later my supply of activated carbon would run out. What would happen if I made and used my own charcoal for a filter?

Finally, chemical treatment seems to be an ideal final step. Preferably with iodine, but if not, then chlorine.

Are there any steps or stages you would consider changing, adding, deleting? There is a stream of running water not far from the house, but as I would not want to use it without treatment. If possible, I'd like to design a system to use as little stored resources as possible. If a syastem can use things you can readily obtain without buying, then it seems to me that is an ideal renewable system in a longterm situation.

Thanks.

Well for the last couple steps what happens when you run out of chlorine?
Why not replace your roofing with some of the materian designed to allow water collection then fill some large tanks there?

After your initiall filtration if your still worried about your water there are a couple ways to go.
1. My personal favorite BREW BEER beer is a great way to make water safe to drink and store.
2. If your bound and determined to have just plain and boring water create a still and boil it look at plans for a flash still like the navy uses.

Dan,

Check this thread.
It has a ton of info and links on setting up long-term water purification systems.

-Blast

My plan is to gather rain from the roof top in my 30gal trashcans (each with a sterile trashbag), strain the water through cloth, then run it thru a 3'x4" activated charcoal filter (made by myself of 4" pvc piping), then boil it for 20 minutes, cool it down, and then add it to my barrel/bottles for consumption.

Trash bags? Are you sure that's a good idea? Personally, I wouldn't want to store water in anything that's not food grade. Trash bags were never intended to store things consumable by humans.

They are not recommended to store food in because they can leach nasty chemicals. Also some trash bags are treated with pesticides. Not things I'd want to add to my water supply.

Maybe you should consider going with water storage tanks for runoff water. Not as cheap as garbage bags, but much more reusable, and made with food grade plastic. Plus if you have it on hand, it will always be full when you need it. You won't need to worry about setting up or when this dry spell will end.

Thanks for the comments.

Roof runoff seems to be a much better idea that trying to transport it from a nearby stream. Although being able to adapt it for either source would seem to be a good system.

I was generally thinking of a system very much like the one Blast posted a diagram of, in the thread linked in his post above. His preflush tube is very much the like idea I had of using a settling tank.

I've read a bit on slow sand filters with bio layers, and my reading indicates they work well. That would be my ideal second step. However, I think I should probably try it out. I also have read about sand as just being a good filter, without maintaining the bio layer. Designing the system to backflush the sandfilter seems more complicated, although I imagine one could adapt the valves off of a pool filter to work. Pool filters might be the thing to adapt for any fitler in such a system.

My idea of adding a carbon/charcoal filter to the system would be to try to account for chemical contamination. I know I'd never be able to account for all possibly chemical contaminants. I've tried to think of a filter that would draw out a lot of chemicals, and carbon seems to do a good job of it, and with some effort, I should be able to create some charcoal, so I could renew that filter. I do not know how effective it might be, but trying to get stuff out is better than not trying at all and slowly poisoning oneself.

Boiling does seem like a good longterm option. Thanks for that suggestion. I could store enough chlorine to do the job for a while. However, I also know about some of the hazards of calcium hypochlorite (that is usually the chemical we call chlorine), and I do not want to store tons of it and risk runaway decomposition.

I've thought about distilling too.

Thanks.

I wonder if you could build a permanent solar distiller out of glass mounted on top of your home or nearby. Let a set amoutn of water flow into it each day and let the sun distill it

Pesticides in trash bags is news to me but sounds reasonable for the intended cargo. I'll do some research on this and get another posting up on what I find. Thanks, Bo

After looking over what Google provided and checking out Wickipedia, it appears that some (most?) garbage bag manufacturers do put some kind of animal repelling chemical into the manufacturing process.

I will rethink that part of my collection plan and find suitable containers to collect the rainwater from the roof.

Dan,

The attached article describes how the folks in Bermuda have collected and cleaned water for 100's of years. Might be a good starting point for some further research. Bermuda Cottages

BTW, that's one place in which I'd love to bug in, er, out, whatever. I've been lucky to have spent a lot of time there, a wonderful place with friendly people and beautiful vistas.

Interesting future thread, how do you cope if you're on vacation and disaster strikes?

A bit expensive, but this might be nice to use for a vessel to hold a filter. http://morebeer.com/view_product/8419/102211

Andy, Thanks, I'll read about the Bermuda cottages today.

While there's no easy way that I can think of to make a continual supply of activated carbon or activated charcoal in a long term emergency, charcoal by itself is still a chemical "filter". Though charcoal won't do as good a job as its activated self, I've read an article or two that stated using between four to ten times the amount of un-activated charcoal in comparison to activated charcoal will do a very good job. It's all about available surface area, and that's the magic of activated carbon/charcoal.

Also, you'll want to create as much surface area as possible to run the water through, so break down the large chunks of charcoal into smaller and smaller and smaller pieces.

So, if you're going to boil your water supply using wood, you may as well collect or make some charcoal while you're at it to use as a filter. It's not going to hurt.

Also, don't burn chemically treated woods...

Additionally, distilling the water before filtering through (activated) charcoal is an excellent purification strategy. Distillation removes everything except for a few volatile organic compounds (VOCs) that evaporate at a lower temperature than the water. Carbon (charcoal) filtration removes all of these VOCs very effectively.

Using the fire to do the distillation, then using the charcoal from the fire to do the carbon filtration not only seems like a very effective purification means, but it seems almost self sufficient as long as you can find wood for a fire.

If collecting rainfall is viable for you, just go ahead and collect some, then have it tested. I think you'll be surprised at what you DON'T find. Do this first, before you go crazy with the purification systems.

From "Harvesting, Storing, and Treating Rainwater for Domestic Indoor Use" from the Texas Commission on Environmental Quality
http://rainwaterharvesting.tamu.edu/drinking/gi-366_2021994.pdf

"The water in a raindrop is one of the cleanest sources of water available. Rainwater can absorb gases such as carbon dioxide, oxygen, nitrogen dioxide, and sulfur dioxide from the atmosphere. It can also capture soot and other microscopic particulates as it falls through the sky. Nevertheless, rainwater is almost 100% pure water before it reaches the ground."

I see you are in NYC. I read a clever way to keep birds from perching on the peak of your roof: screw a sturdy eye-bolt into each end of your roof peak, then stretch some stainless steel wire or strong fishing line between them. That's it.

Sue

What I am considering doing is using a cistern type collection system. In my area, most of the rain falls in the winter and early spring. Then we go 6 to 8 months with unpredictable amounts of rain. So, old timers in this area have done for many years, is have good gutters installed on their houses and outbuildings. Then have the water routed to go into a tank of some kind. I am buying a tank of poly 3,000 gallon capacity to be my above ground cistern. The water will be filtered in a filter similar in some ways to what you describe. If the first tank is a success I will add three more for a total capacity of 12,000 gallons to get us through the dry months. I want to make certain to have plenty of water for our yard, garden and orchard. If power goes in a severe problem we would have lots of soft potable water. My main concern for immediate use is for irrigating our food growing plants.

Wildman, Good luck rethinking your water gathering. If you find any food safe garbage size bags send me a PM. I've been searching for a supply of nonpoisonous garbage size bags for a while now, with no luck.

Intro to distilation
http://lorien.ncl.ac.uk/ming/distil/distil0.htm

How it is done on submarines
http://www.fleetsubmarine.com/fresh_water.html

Solar Stills
http://www.txses.org/epsea/stills.html
http://www.thefarm.org/charities/i4at/surv/sstill.htm
http://www.rotarnet.com.au/users/9/9520/SolarWater/swp.html
http://www.davesplanet.net/solarstill/

If you would like them I have several links to building stills. These are primarily for alcohol but can work the same to purify water.

In New Zealand many properties take their water supply from their own tank, which is filled by rainwater from the roof. No treatment is done, nor is it necessary. A simple diverter discards the first few minutes of rainfall (i.e. until the roof is "clean") and a grating deflects leaves and other debris.

Tank sizing at the beginning is very important, but if you don't get enough rain you can pay for a water tanker to show up (bit expensive though).

A