water pre-filter

[regehr]

over in a different thread @futurafree mentioned pre-filtering water using a 25 micron mesh, before poisoning or using a more serious filter. I just got back from an overnighter where I tried this out and it's a really good idea. the thing I was worried about -- that the 25 micron mesh would impede the flow of water -- was a non-issue, in fact I think the water passed through it more easily than it passes through the bandana that I've been using for this purpose for the last 20 years or so. so anyhow, I'm feeling silly for not knowing this simple trick, which surely either extends the life of the following filter, or makes the subsequent chlorine dioxide (or whatever) more effective by removing the chunkies that are too large for the poison to penetrate easily. this kind of pre-filter will be part of my backpacking gear from now on!

these are cheap on amazon and also probably easily available from any store selling to people who brew beer.

 

[futurafree]

Glad it worked for you.

The mesh + alum + 1-gallon jug is my favorite combo in the desert. If the water is terrible, I add alum to the jug and let it sit anywhere from 20 minutes to overnight, depending on my schedule. Then the jug's handle and translucent walls makes it easy to pour only the clear water through the mesh into my Sawyer bag while leaving the mud at the bottom.

I cut off the top few inches of a water bottle and use the blue Sawyer attachment to screw it on my Sawyer bag before pouring:

 

[futurafree]

While we're on this topic of keeping filters in working order...

I've read many places about using hot water and vinegar to soak the filter when it gets clogged. That might be part of the solution to extending the filter's life, but the two tricks I like that really make a difference are 1.) tapping the filter several times on a hard surface to loosen dirt clogs before each round of backflushing and 2.) only backflushing with distilled water once home after every trip. Minerals from mountain water and my hard water at the house were the culprit destroying filters in between trips.

 

[regehr]

do you mind saying how much alum per liter you've found is reasonable?

your funnel setup is interesting-- I always just take my coffee mug and a nalgene when we go for water. the mug scoops water out of the source, the pre-filter gets pushed into the nalgene, and then from there we pour into the platypus bags or whatever.

my favorite thing is when a friend says "eww... how do you get your mug clean before using it??" and that's my cue to pour some whisky into my mug

 

[RyanP]

So I'm not the only one who uses a cut-off water bottle like that as a funnel! I used to get super frustrated trying to use a bandana or coffee filters without a funnel. That system works fairly well but the extra bulk/volume of the funnel is a little bit annoying if the pack is very full. I might at some point pick up something like this (https://adotecgear.com/products/ult...PouSPLQ4s1hwvh-spAAQ4FKgKHRk4EuiAWZV1oRz24uMF) as a better option.

I'll have to try out the mesh instead of coffee filters (assuming I ever make it out to the desert again); thanks for the tip.

 

[futurafree]

do you mind saying how much alum per liter you've found is reasonable?

1/8 to 1/5 tsp of alum per gallon jug, depending on how silty it is.

 

[fossana]

I slot a small circle cut from a gold coffee filter under the Sawyer o-ring as my prefilter. If the water is super silty (e.g. Escalante river in high flow), I use a Platypus bag, and let the sediment settle out while I set up camp. It catches in the corner of the bag if you pour at an angle.

Agree with @futurafree that my main flow issue is probably backflushing/storing with hard water. I recently found similar prevention advice posted on reddit from a Sawyer rep:

Thank you for reaching out to us and for using our filter. Before storing your filter, we'd recommend backwashing and then sanitizing the unit to maximize the life of your filtration system. Soak the filter in hot water for ~20 min to loosen up any residual particulate built up in the filter fibers. Then we want to vigorously backwash the unit. Water will always take the path of least resistance so make sure you are exerting as much pressure as you can, especially during the first couple passes.

To sanitize the filter, we'd recommend using a weak bleach solution (one capful of bleach per Liter of water). Slosh the weak bleach solution around in your pouch and run it through the filter. After the pouch and filter have been sanitized, let the filter sit upright with sufficient ventilation to dry out before storing the filter in a cool/dry location away from direct sun exposure.