Even the best filters can get trashed if you pump silty water. If your only water source is dirty or cloudy, attach a prefilter to the intake hose (some are sold separately), strain water through a bandana before filtering, or let sediment settle to the bottom of a bucket, pot, or plastic jug.
Get your water from standing pools rather than swift currents (which stir up debris and microbes), and take it upstream of campsites. Safest sources: headwaters, high-country ponds, and glacial melt. Warning signs: farm runoff, hoofprints, mine tailings–even TP.
Problem Leaking input hose Solution Locate the hole and simply wrap with duct tape. If the hose ends split, snip off the damaged end and reattach the fixture.
Problem Sluggish output Solution First, an ounce of prevention. Disinfect at the start and end of each season by pumping a bleach solution (one capful mixed into one quart of tap water) through the filter. If efficiency dips later, it's time for a cleaning. Ceramic filter elements can be scrubbed with a stiff brush, but resin or fiber filters must be backwashed. Technique varies from filter to filter, so check your manual.
WARM AND DRY
Never let leftover water freeze inside your filter; ice can make the filter element crack. Keep it warm by wrapping it in a T-shirt or towel and stashing it in your bag at night. At home, store the filter in a breathable mesh bag so moisture can fully evaporate.