Reddit mentions of Katadyn Ceradyn Replacement Filter Element

Yeah, I agree. Ceradyn is a great option, thanks for bringing it up. For reference, they are available on Amazon:

http://www.amazon.com/Katadyn-Drip-Ceradyn-Water-Filter/dp/B0007U010W/

Actually the Gravidyn is a tiny bit cheaper - this is the one I have:

http://www.amazon.com/Katadyn-Drip-Gravidyn-Water-Filter/dp/B0007U011G/

For anyone who's wondering, yes, the two systems are identical except for the filters that come with. You can put Ceradyn filters in the Gravidyn setup, and vice versa.

The filters are quite delicate, though, and prone to cracking and breakage. You need to inspect them carefully for hairline fractures when you get them. For example, one of the ones in my Gravidyn was broken on arrival. I convinced Amazon to send me a spare one (rather than having to send the whole system back). Also, when I was moving stuff around in one of my storage closets in the garage, I accidentally dropped one of the spare Gravidyn filters on the concrete floor. It was inside its protective cardboard box, but it still broke. I was heartbroken - such a waste of money from a moment's clumsiness. Make sure to treat these things with kid gloves!

For completeness, here are the spare filters - Gravidyn:

http://www.amazon.com/Katadyn-20720-Gravidyn-Replacement-Element/dp/B0007U011Q/

And Ceradyn:

http://www.amazon.com/Katadyn-Ceradyn-Replacement-Filter-Element/dp/B0007U0116/

Hope it's ok posting links like this... I have no stake, not connected with the company at all etc.

The Monolithic filters are also interesting, and they claim to remove arsenic and lead as well. I would be concerned with arsenic in the surface water around here, though it might only be something that is in ground water (i.e. from wells etc). Anyway, these are very simple and cheap too, you can make a bucket filter around one of these little things and have a basic system. I don't know how much formal testing they have had, but they seem to be used a lot in 3rd world countries.

http://www.monolithic.org/water-filters

http://www.monolithicmarketplace.com/collections/frontpage/products/just-water-ceramic-drip-filter

As I said earlier, if I ever have to use the creek water, then I intend for the Monolithic to be the first stage, then treat with calcium hypochlorite (pool shock - 78% TurboShock from Poolife is the best I've found), then treat again with the Katadyn to remove the chlorine and just do another round of filtering in general. I figure I should be covering my bases with this.

http://www.amazon.com/POOLIFE-Poolife-TurboShock-1-lb/dp/B0017SSFU6

And also in case anybody's interested: To treat water with calcium hypochlorite, first make a bleach solution (NOT FOR DRINKING!) by adding a heaped teaspoon to 2 gallons of water. Then you can treat drinking water with this by using 1:100 ratio (i.e. for every 1 part bleach solution, 100 parts water). This should make it obvious that the calcium hypochlorite is pretty concentrated stuff - you shouldn't be trying to treat drinking water directly. First make the solution, then use that to treat the water. For reference, the 1:100 ratio translates into roughly 2.5-3 tablespoons of solution per gallon of drinking water, or 3/4-1 cup to every 5 gallons of water (if you're treating by the bucket). I give a range since it might be easier to measure 3 tablespoons and 1 cup rather than fractions like 2.5 and 3/4, and I think it's probably true that a little over treatment won't do any harm, especially if you are filtering it out anyway. Let the water stand for at least half an hour when treating, the longer the better. Contact time is important for killing the viruses etc.

Also, the pool shock is hard to store safely, since it produces chlorine. Anything metal will get corroded over time. The best method I have found is to use the mason jars with the metal canning lids (the ones that come in two parts). The 1 lb packs of TurboShock fit nicely in a 1/2 gallon jar. I know the lid is metal, but it has a plastic coating on the inside, and those lids are the best sealing I have found. I can put three jars inside a plastic 5 gallon bucket that has been sealed with a Gamma spintop lid. Then I can check on them every few months, and I'll know immediately if the jars have been leaking inside the bucket, because you'll be hit with the chlorine as soon as you open the bucket. I figure if the metal lids start rusting, then I'll just see what their safe lifetime is, and treat them as consumable items. A box of lids is only a few bucks, so replacing them every six months or year or whatever is no big deal. I also wrap the jars inside the bucket in bubble wrap, just so they won't break against each other if things are thrown around during an earthquake. With 3 lbs of the calcium hypochlorite, I'm ready to disinfect a LOT of pond water! Maybe also useful as bartering material in the event of a long term service outage, you never know.

Oh, and one last thing - I got a set of long handled measuring spoons, so that I will be able to reach inside the jars to get the pool shock out without having to tip them up or whatever, risking getting this toxic substance on my skin or in my eyes (big nope).

http://www.amazon.com/ChefLand-Set-Sizes-Stainless-Ingredients/dp/B00AEUR6K8

I know metal isn't good with calcium hypochlorite, but I'm not storing them with the stuff and their contact time will be minimal, and I'll be washing them after each use. I just figure it's useful to try to consider the practicalities of how you will use stuff in reality... also, I'll probably not make 2 gallons, but rather only 1 gallon at a time, which will mean a heaped 1/2 teaspoon of pool shock. And how to store the bleach solution? I found some nice 1 gallon jars with plastic lids for that:

http://www.amazon.com/1-gallon-USDA-Fermentation-Glass-Jar/dp/B006ZRBGSC

The solution should be good for a couple of weeks, I think, if stored in a cool dark place. I guess you could also use it to treat your bucket toilet, so maybe you won't waste much.

Sorry, as you can tell I have thought way too much about this stuff. :P