The Platypus GravityWorks hydration system uses gravity to filter water. It comes with 2 bags, one for dirty water (unfiltered) and one to hold the clean water that has passed through the filter. Fill the dirty bag from a river or lake, connect up the filter, hang the dirty bag well above the clean bag and then let gravity do the work.

Depending on the cleanliness of the filter and the dirty water the system will filter a liter of water in around 5 minutes. For long hikes away from civilization, I recommend taking a spare filter. Chances are that the filter will need back-flushing at the most inconvenient time. A spare filter is one of the very few items where a back-up is worth the extra weight. Sometimes, the air in the filter and pipes can slow the process down. Resolve this by squeezing some of the air back up the pipe into the dirty bag.

Platypus also offers a number of hydration reservoirs (bladder) which are compatible. Make sure your reservoir has the screw on drinking tube, rather than the clip in kind. These come with a normal hose for drinking from. Getting the water from the clean bag into your reservoir can be a challenge. Firstly because most packs have an internal sleeve for the reservoir, taking it out of the pack usually involves emptying the pack somewhat, getting the full reservoir back in is even more challenging.

TOP TIP: Add adapters to the hoses between the Platypus GravityWorks hose (after the filter) and halfway along the drinking hose. Now, (keeping the reservoir in your pack) just detach the drinking hose and attach the Platypus GravityWorks filter to fill the reservoir inside your pack. When traveling in a group, simply switch from bag to bag and attach the filter system. Another benefit of using this system in a group is that if all your systems are compatible, a failure is more easily remedied.

Platypus also offers bite valve covers. Whilst these do a good job of keeping the dirt away from the mouthpiece, any dirt which finds its way inside (and it will) is more difficult to clean.

Likes

• Simple, small and light
• Great for a group with the same system
• Let gravity do the work

Dislikes

• Can be slow
• Filter can get clogged and need cleaning

Overall

A great bladder / water filtration system