Backflushing at a glance
- Tool
- Syringe or coupling
- How often
- Little and often, on the trip
- Restores
- Most of the lost flow
Why a filter slows down
Everything a filter removes stays on its inlet side. Over a few days that layer builds up and flow drops, which people interpret as the filter wearing out. Usually it isn't worn out at all, just loaded, and pushing clean water back through in the reverse direction lifts the sediment off and restores most of the original flow.
How often to do it
Most filters ship with a syringe or a coupling for exactly this, and the instinct is to save it for the end of the trip. Do it more often than that. Backflushing daily on silty water keeps flow high the whole time and stops the element ever reaching the badly clogged state that's hard to recover from.
Backflushing without the syringe
If you've left the syringe at home, the field version works: fill a bottle with clean filtered water, connect it to the outlet side, and squeeze hard. It's less effective than the syringe and considerably better than nothing. What you must not do is let the filter dry out fully with sediment still packed in it, because that sets hard.
What this means when you're choosing
- An included syringe or coupling, since you will not do it without one
- Whether the filter can be backflushed at all, because some cannot
- How the maker says to do it, which varies by element
The common mistake
Saving it for when the filter has almost stopped
Sediment compacts on the inlet side and gets harder to shift the longer you leave it. Backflush little and often, on the trip rather than after it, and a filter lasts years instead of a season.
Common questions
How often should I backflush my filter?
Whenever flow noticeably drops, and daily if you're drawing from silty water. It takes under a minute and it's the main thing that determines how long the filter lasts.
Can I backflush without the syringe?
Yes. Attach a bottle of clean filtered water to the outlet side and squeeze it back through. It works less well than the syringe, so carry the syringe when you can.