I decided to buy the Platypus Gravityworks system. I picked the 2.0L version. I added a carbon filter. And I purchased a second filter as a backup. You don't want this system to fail when you're out in the woods. I got the whole package at MEC. The filters are reportedly sensitive, meaning DON'T DROP THEM! I dropped the second filter carrying it out of the store. D'oh! Well it was in a cardboard box. The Platypus is "Prong One".
The above items currently sell at MEC for $105, $50.50 for the extra filter and $18.50 for the carbon filter (which is supposed to improve the taste of the water you filter).
"Prong Two" is a Steripen. LT bought the Steripen. I think it is the Steripen Ultra Water Purifier, currently $105 at MEC. It's easy to use and also very sensitive. I'm a bit nervous using it, only because the cap is so darn tough to pull off and I'm afraid of dropping the whole thing into my water bottle when stirring it.
On our first trip last year we needed a method to draw more than 2 litres of water out of the middle of the lake. I had one of those plastic collapsible cubes from Canadian Tire from my car camping days. It has a spigot with a red cap on one corner and holds probably 5 litres. The collapsible part was good, LT could stuff it in a side pocket of his backpack so that it was handy while we were in the canoe. However, it was hard to fill with an opening of less than 2 inches in diameter, while hanging over the side of the canoe. I sit in the front, so I never really see what goes on back there, LOL.
It was obvious the cube had to be replaced. I bought a very large "dirty water" bag. It's like a big dry bag with a spigot and a handle to hang it. It has a mouth the width of the bag and is much quicker to fill. It's still pretty heavy when LT is hauling it into the canoe.
We (well, he) hang this bag as high as possible and then fill the "dirty" bag of the Platypus system at the campsite. I think the big bag holds about 8 litres of water. Plenty to cook, wash dishes and fill Nalgene bottles for the next day's trek.
If I'm boiling the water to cook with, we filter it but don't sterilize it with the Steripen. If we are washing dishes, that water only gets the filtration, not the sterilization either. However, we do sterilize our drinking water right in the Nalgene bottles. We each carry one bottle, both bottles are 1L ones. The Steripen defaults to 1L when you turn it on. You dip the Steripen in the water in the Nalgene bottle and stir for 80 seconds to sterilize that one litre. That's it.
On one of our trips the Steripen got fogotten (we missed it terribly). I was boiling water for drinking. Lesson learned: do NOT put hot water in a Nalgene bottle then hold it by the lid alone. The hot water changes the size of the lid link and the bottle enough that the bottle slid out, banged on the ground and sprayed boiling water through the air onto my face. Fortunately it travelled through enough air to cool down a bit and I did not get any serious burns. Silly mistake I won't make again.
Issue with the gravity fed system: it can get slow, really slow. The filter catches the particles from the lakewater and they build up. It's easy enough to backwash it. It just takes time. The way we set up camp, one of the first things we do is start the filtration system going and it filters while we're setting up the tent, the hammock, the bug shelter, etc. We differ on philosphies on how to best make the system work. I swear it runs better if the plastic tubing is fully stretched, so I often lay the clean water bag on the ground. LT likes to ensure there are no bubbles in the tubes when he sets it up.
We are both happy with the water filtration we are using. When we get home I take the Platypus system and run clean water through it hanging the dirty bag on the shower head in the bathroom. I backwash the filter(s) and rinse out both bags with clean water with a teeny bit of bleach in it. I have a plastic bottle (I think it had some sort of drink powder in it originally) with a lid that I store the spare filter in when tripping. It gets wedged in pretty tight in my backpack, the bottle protects it from being squeezed or punctured.
To help with the flavour of the water I have a product, True Lemon, that comes in little single serve envelopes, like fake sweetener, and I add it to my Nalgene bottle for drinking. LT uses some type of Powerade drops that are blue and have a bit of flavour to them.
The system at work below: