How do you know if a filter is damaged from freezing temps.

As a general rule, if a water filter has been frozen too far, it develops leaks in the filter element, and then raw water will flow through it too quickly and not get properly filtered.

I don't know if this method still works, but the old method was this: Dump some red food dye in some water, and then pump it through the filter. If you see any pink showing up on the clean side, then you probably have a problem.

I saw a $1000 Katadyn expedition filter that had been frozen, and then the ceramic filter element shattered. We saw pure red water going out on the clean side.

–B.G.–

I would say that its F'ed..

From Sawyer's website:

How do I care for my filter during freezing weather?

Before initial wetting
Filter is safe from freezing temperatures if it has never been wetted.

After initial wetting
While there is no definitive way to tell if a filter has been damaged due to freezing, Sawyer recommends replacing your filter if you suspect that it has been frozen.

During trips
If you are in freezing temperatures we recommend that you store your filter in your pocket or close to your person so that your body heat can prevent freezing. THERE IS NO WARRANTY FOR A FROZEN FILTER

Use it to filter water from the bottom of a beaver pond and if you don't get sick try a cow pond and if you still don't get sick try… Ya know they need to make a test granule of a micron size just bigger than the filters micron rating that you can mix with water, filter then a way to test for the granule. Till then I'd buy a new filter ;^)

When in doubt, throw it out. That sucks, but it's better than getting sick.

Everyone keep that in mind for leaving water treatment gear in the car too.

You needed and excuse to buy a mini anyway, right?

Thanks, guys. I may try the food coloring, but will probably go ahead and order a replacement.
To what Dale said about leaving stuff in the car:
My trip got cut short as I received a phone call that had me returning home suddenly this morning. Last night I was camped on a 2 mile loop trail by the actual trailhead.
Stopped at a rest area on the way home, and the Clorox wipes in my glove compartment were frozen solid. Nice.

I believe this was disucssed last year. In short food coloring won't work.
http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=13959&startat=20

Food coloring is not a prticle. Instead it is a water soluble material. and the coloring molecules are much smaller than viruses. So the food coloring will go right throught he filter. If you have a filter with carbon filter to remove test and chemicals, food coloring willl tell you if the carbon filter needs replacement. But it won't tell you if the particle filter is bad. Sawyer is just a particle filter.

The only way I know is to measure the flow rate. I took a bladder and attached a 3 foot hose to it and at the end put my filter. I put one quart in the bladder and then timed how long it took the water to fully pass through the filter into a bucket. It took about a 1.5 minutes. If ice damaged it it, I believe the time would be a lot shorter. Sawy has several different filters for sale so the time for water to pass through is different for each type.

Thanks for the idea Surf!
I wish I thought of doing this when I received my mini. I started using in November – all subfreezing night temps, but I have kept it in the sleeping bag at night. I should have kept it in a pocket during the day…

A used filter with some clogging and freeze damage may give the same flow rate as an unclogged filter with no damage.

If you're talking about a $100 filter I could see trying to rescue it, but the Sawyers are cheap enough make the possibility of becoming a human poo fountain not worth the risk. If you had an intestinal bug and someone offered you a cure for $20, I'll bet you would happily pay double.

The food coloring idea may stem back to the days when First Need provided a vial of blue dye to test their filter with. The ceramic filter in an enclosed housing could be damaged from dropping as well as freezing and no way to inspect it. No idea what was in the dye. IIRC, that was a 0.02 micron filter.

That is the major "con" of filters and one reason why I have never owned one.

Went ahead and ordered a new one. I did not want the mini. The full size one lets you attach a Platypus by using a "water tornado", which I find a very handy feature. You can backflush with it, and it makes filling my Platy bottles simple. I use an Evernew for the dirty water side out of concern for durability with the factory bags(Platypus doesn't work with the threads), and usually just sit down with a leg over it to "squeeze" my clean water out.
http://img19.imageshack.us/img19/2749/dscn9401h.jpg

I once found myself in the same situation with a Platypus Gravity filter and wasn’t sure whether the hollow fibers were damaged by freezing temperatures.

Cascade design has the following information on their FAQ website

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What about freezing?
Once you have used your CleanStream™ filter and wet the Hollow Fiber filter media, the fibers will remain wet for a very long time. Therefore, it is important to prevent it from freezing, which can permanently damage the filter media. If you are traveling in areas where you are expecting freezing or near freezing temperatures, bring the filter into your tent, or even your sleeping bag. The included, watertight hose barb covers will prevent any leakage wherever you store it. If you think your filter may have been damaged by freezing, perform a Filter Test before the next use.

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The test described in the linked PDF document is really easy to do – just blow through the filter from the clean end. If you can’t do it, the filter is OK. If you can blow air through it, it is damaged.

Assuming that the Sawyer filter uses similar hollow fibers, the same test might work for your filter.

Manfred

It s easy to attach a platy to a mini using a short hose and the same fitting used for a platy drinking tube. The same fitting can be rigged with the Sawyer barbed hose fitting kit.

I think you're making the wise choice in replacing that thing.

Good decision on replacing your frozen filter. I wouldn't have trusted that thing anymore either.

Doubting the efficacy of your water purification method is never fun.