Does a Sawyer Mini lose its effectiveness over time?

With effectiveness, I assume that you mean will it filter out the same particulate sizes.  The answer is yes.  What happens is debris will build up on your filters.  Classically, this makes your filter better as it creates a labyrinth for particles to get trapped in.  As the labyrinth grows, your flow rate will tend to diminish as well.  My 2 cents.

or, just one event of leaving hard water in the filter will plug it up

that could be when you first bought it, or after years of use

it’s not like it gets used up over time until it gets full and you then have to discard

Yes, when I refer to effectiveness I mean ability to filter out pathogens. I’ve never had any issues with my Mini clogging or slowing down. Like I said, I back flush after every use and I’ve been filtering water with a good PH.

I like to replace my filters yearly and consider the Mini’s lifespan to be about 100 gallons then it filters to slow to be useful.

Just don’t freeze it.

So if the Mini freezes will it stop working or does it just mean that it won’t properly filter out all harmful particles? I’ve had mine down to about 30 degrees a couple of nights in my pack when I forgot to put it in my sleeping bag with me. I don’t think it froze hard. Obviously I’m a bit overly scared about water borne diseases.

Freezing MAY damage the filter.  The problem is that there isn’t a reliable or simple test to determine if the filter is still good or not.  When in doubt, I would chuck it and buy a new filter.  Out backpacking, just keep it from freezing.  My 2 cents.

My Squeeze has frozen a few times.

I always shake the water out before hand so there’s only water in the tubes, but they’re designed to stretch when they’re back flushed, so it doesn’t matter if they freeze.

But, like Jon says, the problem is there’s no way to know if it still filters effectively.

If you don’t shake the water out then the case will probably crack.  That would be obvious.

Or if the connection between tubes and housing cracks then if you squeeze water through it it would be obvious, little pressure required to get water to flow through.

My Squeeze requires normal pressure to squeeze water through so it’s probably good.  When I filter tannin water, the output water is clearer and when I backflush there’s a lot of tannin in that, so the filter must be doing something.  But Jon’s probably right, I should just chuck it.

Too bad there isn’t a way to have some colored particles of small diameter to test to see if your filter works.

…so it doesn’t matter if they freeze.

Are you speculating here or do you have an authoritative source, Jerry?

This reminds me of Daryl and Daryl’s detailed experiences with the Sawyer Mini several years ago.  He was having issues with it, and trouble back flushing.  One thing he noted is that water should not be left in the filter between trips. or else it would be very difficult to back flush without home water under much higher pressure than available in the field.

After reading about his experiences, I decided to just buy a new mini before each trip, which average 1-3 weeks.  Were I thru-hiking longer distances, would use a better filter cartridge; but the mini worked fine for the shorter trips.

As I recall from that thread, it was generally accepted that freezing water in a mini would end its effectiveness.  But with trips in the summer and shoulder seasons, using a tent, there have been no problems.  My filter is at:  https://backpackinglight.com/forums/topic/99643/              Note the use of a prefilter taken from an old pump filter.  Am still using the filter with the ketchup pump with a new mini for each trip.  They have been cheapest at Walmarts.

Yes, I am speculating about Squeeze not being damaged by freezing

I hate to throw things away that still work, just in case they may not work

Note to self: don’t drink Jerry’s water.

I’ve never got sick drinking water :)

I’ve never got sick drinking water :)

Speculating again, are we?  :-)

I don’t think that’s speculative – although I could have got sick but didn’t know it

It was provocative though in that me getting sick is sort of irrelevant.  The question is, out of a population of users, if they treated their water, would there be significant fewer people getting seriously sick.

An individual remembering their experience is anecdotal and not very useful information.

Sort of like covid, masks, and vaccines.

The Sawyer Mini needs a faucet-pressure backwash a few times each season. This is what I made to do that. Fittings are double-female garden hose thread, male garden hose to 3/8 inch hose barb, and then 5/16 i.d. vinyl tubing. I softened the tubing in hot water to slip it over the hose barb. The choice of fittings was based on what was available at my local hardware store.

Adrian, do you reduce the 60 psi (nominal) tap pressure with an inline valve to preclude damage to the membrane?

No valve, but I just measured my water pressure–it’s 44 psi static. Also,  the vinyl tubing isn’t clamped to the filter output end. I just hold it there. So I don’t think there’s much chance of excessive pressure. But it’s worth wondering about.

Debate is all well and good, but I’ll stick to buying a new mini Filter for each trip at the $20 or so Walmart price.  And will still backflush and drain, and keep at room temp, after each trip for use hiking for only a day or so.

Do not have to speculate.  I did get giardia twice.  First time was from a stream that looked free flowing and pure; but after drinking and hiking a bit higher, saw that the stream drained from a marsh.  Took the pills right after the trip – no problem except the tummy ache.

Second time was a doozy.  Same symptoms, but how could I have got it in winter?  And why did the same meds not work?  Subsisted on tetracycline for a long time until found that a family of squirrels were living in the well.  Cleaned out the well, and had a new one put in some distance away.  Used jugs of spring water until the new well was done.  The biggest challenge was persuading the doc what happened, but succeeded, and the symptoms resolved.  One catch, long term exposure can do damage to the gut, and cause chronic disease about which little is known.  YMMV – the symptoms can be different for different folks, so generalizations are seldom helpful.

Jerry is quite right. About 20-30% of the population never have guardia symptoms, though they may carry it. He might very well be one of those people.

sort of like Typhoid Mary?

Yeah, sort of.
No, Sawyers don’t loose effectiveness over time, but, they go slower and slower till you get fed up with using them. At least that’s what happened to me. I get somewhere around 6-7 months use out of a Sawyer Mini, before it just takes too much effort and time to bother with. After a couple, I gave up.