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Sand and Gravel water filter- HELP Answered

Okay so I have been charged with finding out how to build a simple sand/ gravel water filter for use at scouts on Thursday and I have come up with ZERO... Does anyone know enough about it to explain to me in laymans terms on how to construct one... or rather what grades of sand/gravel i need?

I'm planning on using a pop bottle, and layering the sand and gravel inside it.... using the screw top end as the tap.... I have a BASIC idea of what i need... I just want to be sure it works!

Thanks guys and girls




5 years ago

All of us give ideas for the filtering the water to remove primary clarification of water by using sand filter bed/ charcoal/ chlorine tablets etc.

I suggest to use the laptop adaptor 24 V DC/1.04-5 AMP Supply & connect two small plates may SS or iron 5 cmx3 cm length with cables for using as anode/cathode and immerse into the water for 15 minutes.

It will give very good effect on water , which not only removing impurities but also the micro organisms remain in the water without changing the odor of water

(Global Challenge badge?)

To make a "survival" filter:

Starting at the bottom, layer of sandpit sand, small gravel, large gravel, and top off with stuffed in straw or grass. Starting at the top, each layer removes progressively finer particles.

Pour in muddy puddle water.

What comes out of the bottom should be reasonably clear, but on no account must it be drunk or tasted.

If you have the facilities, boil some of the filtered water dry in a glass or white container to show them why - the crud left is dissolved minerals and other organic substances, including bacteria and other microscopic bugs that can cause serious illnesses.

As an anecdote, you can mention the time the Chief Scout, as a last resort, rehydrated himself by giving himself an enema of dirty water - the colon absorbs the water, but not the infectious and toxic agents.

Are you kidding about the enema story ? Anyway colon absorbs a lot of organic and inorganic molecules, drugs, germs and parasites . If you drink by moutth you could feel some horrible taste , stink or animal moving and you could spit it out . I would seriously consider some kind of alternative to this. Didn't the Chief Scout have any kind of bottle to chek the water and try some kind of last chance treatment of the dirty water and if he hadn't how did he got water into his own colon., did he use some some kind of ayurvedic or yoga practice sitting in an awfullly pest populated pond ?. I must say it's quite an incredible tale to me, I advice against that last chance tecnique..

Yes, it's true, and you're missing the point - it *is* a "last chance technique".

YOU went there!! I just posted the video of it!

<dodges bullet by getting distracted and not hitting the insert video button earlier>

The Biosand filter is fully described here: www.cawst.org complete with a downloadable manual.

It is built with 2" of gravel at the bottom, then 2" of smaller pebbles, then 21" of sand on top. It is a version of a "slow Sand filter". The bio layer builds up over about 30 days and will then purify the water. Until that time you must boil, solar purify, or chemically purify the water before drinking it.

The filter may be made in other containers than the concrete container that is described. Plastic barrels, trash cans, large diameter pvc pipe, and many other clean water tight containers can be used.

Cities use "slow sand filters" on a larger scale to supply entire cities with safe, clean, pure, drinking water.

i know i'm late, sorry.

.... actually, kiteman, there are filters that use just sand that are completely safe to drink from (biosand filter). i learned about them from a group who teach people in africa how to build them. if i'm remembering correctly, the sand cultures a bateria system that cleans the water. however, i think they take like a week or something to get started, and they were like 1'-1'-3' in size, being 3 feet tall.....

they're great for africans, because all they need is sand, make the container out of concrete (basically sand.....) and fill it with progressivy larger sand particles...

amazing.... that buisness card was still in my wallet.... the goup was called active water, activewater.org

i couldn't find anything specific on their website, but they give this information away for free to africans, so shoot them an email, they will probably tell you.

That's not Kmans caveat, its the Scouts derriere-covering, so they can't get sued if someone tries to dring from it.


... plus, it means you can use any old sand you find lying around.

Hmmm, are you going to mix up a batch of mud water, filter it, boil it and then attempt to drink it?

I would have thought that is in the scout manual but it is a simple scientific experiment to filter out the big gunk and progressively going to smaller and smaller filter or trapping particles. Strain through fabric first - cheesecloth, then gravel, then sand, activated charcoal is in the mix when you are trying to get rid of some other nasties in the water. Just make a few holes in a tin, layer at bottom with sand, coarser and coarser gravel on top. The mud should be trapped as the water settles through. Making it safe to drink with chlorine tabs, boiling or distilling is another matter.

Any outdoors survival manual will have better details.
Good luck.

Sadly the scout manual doesn't have HALF of what it once had.....I would love to have my old one...it'd have a place right next to my Dangerous Book for Boys on the book shelf :-)

Probably for a slightly elevated price? thanks, I will check it out in case I am wrong ;-)

Tricky. Getting a Scout-interesting flowrate is going to take a decent head of pressure. Otherwise, the filter design is pretty sound, though I'd try and put a piece of geo-textile between the gravel and the sand, to stop the sand coming through the gravel bed.


Just go to the pet store and get the media for the aquarium filter - polyester floss, gravel, and sand.