I often spend weekends on extended backpacking trips where water needs to be filtered from lakes and streams before consumption. For years the most popular filter for outdoor enthusiasts was the Hiker by PUR (now Katadyn). The filter itself is very well designed, featuring great throughput, reliability, and easily replaceable parts. Unfortunately, the rest of the system is appallingly designed for the user. The pump handle, the output line, and the filtering process are quite poorly executed.
The stock pump handle for the Hiker is a large flat part, which fits awkwardly in the palm, protruding to one side of the pump shaft. This design is not comfortable for the hand and puts a great deal of torque on the pump shaft due to asymmetrical loading. This causes the pump to bind-up easily and induces flex which makes the pump feels insecure and fragile. It does, however, store very compactly.
The clean-water output line is a long silicone hose attached to a plastic cap. The cap does not physically attach to bottles and is wont to pop out during use. To ensure it stays in place it must either be held in place or kept perfectly still while pumping. In storage the output hose and intake hose get shoved into the same bag where they can easily become entangled and contaminated. Avoiding contamination requires the user to remove both hoses, bag them separately and carefully avoid letting them touch. I often use my filter 2-3 times a day making assembly and disassembly a monotonous task.
Actually filtering water requires the user to manage 3 separate parts: the pump body, the non-ergonomic pump handle, and the output hose/cap loosely placed into a water bottle. Like most people I only have 2 hands, enough to pump water but not to manage the bottle at the end of the ouput hose. I have seen hikers clamp the bottle between their legs while perched precariously on wet rocks at the riverside, bottles balanced on tree roots next to lakes, or held by a second person if available.
Fed up I decided to redesign the filter. While making my prototype I decided to retain as many original parts as possible. Rather than redesign the entire housing, I created an adapter that clamped onto the filter to attach the improved parts.
A machined polycarbonate cap, shaped like a water ripple, is attached by a pivot and clamped into position via a quick-release. Integrated threads allow the ubiquitous wide-mouth and narrow-mouth Nalgene bottles to screw into securely for hands-free bottle management while pumping away. In use the cap pivots into a filling position, holding water bottles next to the filter. In storage the cap tilts the output end of the line upwards and away from the intake line, which is conveniently wrapped around the filter, eliminating the possibility of contamination. The output cap is now an integral part of the filter, with no loose lines to manage, one less item to hold on to, and improving the health safety.
I decided a T-handle which could be used with 1 or 2 hands would be ideal for axial loading and pumping comfort. To allow the handle to store as compactly as possible the handles can be released from the shaft. They are attached by shock cords which keep all the parts together and facilitate quickly snapping the handle together. For storage the adapter holds the loose handles tightly against the space around the sides of pump shaft resulting in a configuration that is comparably compact to the stock arrangement. All handle parts were machined out of solid polycarbonate for strength and durability.
The resulting arrangement regularly fetches admiring glances out on the trail, with others often asking to try the prototype and complaining about how poorly their filters work. It has accompanied me on numerous trips into several countries and numerous national parks without a hitch. When hiking in groups it has frequently become the "workhorse" filter used to pump water for the whole campground. The slight increase in carrying weight and bulk is completely worth the enormous improvements in usability, security, and safety.