Start with the part that fixed my creek-bank problem.
Sediment is what kills a filter. Not bacteria. Mud.
Push muddy water straight at a fine membrane and it packs up and quits. That's exactly what happened to me.
PureFlow runs the water through four stages before it ever reaches the fine membrane.
A coarse screen catches the sand and the visible junk. Medical-grade cotton takes out the fine silt.
A stabilizing layer evens out the pressure so it draws easy instead of feeling like a coffee stirrer. Then the 0.01-micron membrane does the fine work.
The first three stages exist to protect the fourth.
That's the whole reason it goes the distance.
One straw filters up to 1,800 gallons.
Drink a gallon a day and that's close to five years of water out of something the size of a marker.
It needs no power, no batteries, no chemicals, and no fire. You put one end in the water and you drink from the other.
Or you screw it onto a regular water bottle, fill the bottle with the dirty stuff, turn it over, and squeeze.
Now you're filling a pot or a canteen instead of putting your face in a creek. That's how you get water to more than one person.
And the answer to the question I get asked most:
No expiration date when it's stored dry.
There's nothing chemical in it to break down and nothing electric to fail. Keep it dry. Don't let it freeze, because freezing wrecks the hollow fiber. If you do use it, let it dry out before it goes back in the bag.
That's the entire maintenance schedule.
It's third-party tested for bacteria and protozoa removal, and pressure-tested for membrane integrity and leak resistance. It's made with FDA food-contact-compliant, BPA-free materials.
The twelve-dollar ones are untested factory parts in a plastic tube.
Don't gamble on water.