A home made water purifier is a great idea, if you're a kid looking for a science project.
  They make for interesting conversation in Boy Scout meetings.
  And, it's something for the kids to do on a rainy day.
It's almost like a magic trick, if you get it to work right.
  Of course, you wouldn't want to drink the water that was cleaned by a home made water purifier.
  They aren't really purifiers.
What you can do is remove some dirt, but not bacteria or other contaminants.
  The best way to show the effect is to gather a bowl of stinky pond-water.
  Place the bowl on top of a box, that's about a foot tall.
  Make sure it's sturdy enough to support the bowl.
Place an empty bowl on the table, beside of the box.
  Braid yarn into about a two foot rope and place one end in the dirty bowl and the other in the bowl on the table.
Go do something else for about an hour and you'll come back to find that the pond-water was absorbed by the yarn rope.
  It traveled along the length of the rope and dripped off into the clean bowl on the table.
Eventually, all of the pond-water will be absorbed, but mud dirt and debris will stay in the bowl.
  The water will "look" cleaner.
  But, is it really clean?  If you have a microscope, you can put a few drops on a slide and you are likely to see organisms moving around on the slide.
Those organisms cause waterborne illnesses.
  The symptoms are similar to food poisoning.
      In addition to a home made water purifier, you might also want to get a do-it-yourself testing kit from Home Depot or a similar store.
  With it, you can show the kids what's in the tap-water and explain why you have a purification device on your faucet.
  Don't have one?  That's a big mistake.
Public treatment facilities can only do so much to protect our health.
  They get rid of the majority of the organisms that can make us sick, but they use chlorine to do it.
  Chlorine, itself, is not very toxic, but the compounds that are released during the chlorination process cause cancer.
  There is no doubt.
  It's not a theory or a possibility.
  It's a fact.
I'm not sure those do-it-yourself kits test for them, but they do test for chlorine.
  If you have chlorine, you have the cancer causing compounds.
A home made water purifier cannot be used instead of an advanced purification system.
  The processes are too complex.
  But, if you use it, the do-it-yourself test and show them the steps that are taken by facilities (you can see that on the internet), you may be able to help your kids understand the importance of water conservation and purification.
When I was a kid, we visited a treatment facility and I've been interested ever since.
  So, make a home made water purifier for the kids.
  And, if you don't have one already, get a purification device for your kitchen sink.