Water filters, what to look for.

I used to have a 'thing' with water filters, so I tried and tested a lot of them.

The one's I have owned and used:
- Katadyn Mini, with the external carbon filter element.
- First Need water filter, old model.
- Nerox gravity filter
- Katadyn CAMP
- Gatekeeper
- Pre-mac personal water purifier (PWP)
- Katadyn Pocket
- MSR waterworks
- MSR Mini waterworks II
- MSR Mini waterworks EX
- Katadyn Mybottle
- Tulip water filter (have not used this one, just own it)

(DIY, Millbanks, note included on the list)

I could have had more, I just can't remember. Having had so many water filters, there are a few things I can tell you about them:

Filter types and maintenance
There are two main types of water filters: Ceramic and fiberglass  There are also others, but the manufactures are bit silent on the used type of filter material (example: First Need). Hollow fiber technology has also started to appear, but primarily in smaller sized filters.

Fiberglass cannot be scrubbed clean. You can flush it and with some models backwash it. When badly clogged this however might not do this trick. This makes it hard to determine when the filter will be unusable. However the fiberglass is pleated and there has a very large surface area, making the flow rate fairly high.

With ceramic you actually scrub of a layer of the ceramic, exposing a new fresh layer of ceramic to work with. However I have found that just wiping the dirt off, works too depending on the dirt. Wiping obviously creates less wear on the filter then scrubbing. Since it's only the surface which filters the water, these are low on surface area and relatively slow.

For storage, dry the filters first and make sure not to expose the filter to freezing conditions.
As with everything with o-rings, keep them lubricated and keep a few spare o-ring.

Pumping (or not):

Pumps/filter size; size and type
Small pump and small filter with tiny amount of surface area = little water for a lot of work.
Big pump and large filter with loads of surface area = more water for less work.

I started out with a Katadyn Mini. It really has a mini pump and filter inside. OK for making suspicious tap water safe, but for any large quantity it quickly becomes too much of an effort. The small pump and filter just requires a lot of manual labor and the small filter gets dirty fairly quickly. The advantage of carrying a small and light filter has to be paid in the form of a lot of labor when you pump. All mine other (bigger) pump filters where much easier. What the balance is between weight/size versus labor is yours to make. I prefer the bigger ones.

Types of pumps:
There are long rod type of pumps, you have the short and fat pumps with lever action and you have the two in double action versions. I can't really say which ones are better. Single actions pumps are more simple in construction, but takes a little longer. If the filter screws directly on a bottle, a pump in the middle (right in the middle of the bottle) is best. If it's off set, you really need to hold the bottle steady. I do like the lever action pumps like on the Waterworks models of MSR.

Squeezing
Squeeze bottles are interesting. You don't filter water in advanced, but filter it when you drink. This creates a few issues. Squeezing a bottle to filter water for other purposes then drinking is a lot of work and is hard work for your hands. So what do you do, when you need to carry more water? Fill you other containers with dirty water? It also seems to be impossible to filter all the water from the bottle. There is too much airspace left, to be able to filter the last 1/3 - 1/4 of the water.

Gravity
Mine favorite (I’m lazy). Fill the container and wait. Just check if no dirty water is on the outside and following the hose on the outside down to your clean water supply. Easy, simple and let you do other stuff.

There are three different types of gravity filters:
- Filters mounted in large fixed containers (large stainless containers, plastic containers or even buckets): Best for (semi) permanent use. They are sturdy, simple and just easy to use. Most vesions allow multiple filter elements to be installed to speed up the filter process. They are however very large and relatively heavy.
- Filters mounted in a waterbag (or in line). A more portable alternative to the large fixed containers. Best are the ones which connect to a clean water bag (a open container allows for contamination).
- Siphon type water filters: creating the vacuum to get it running can be a little hard. Sucking on the hose might not be the most hygienic method. Some do have a little balloon bellow to get them started. They can be used with any water container large enough to hold the filter. If there is a balloon bellow, it is a additional part which can fail.

Hoses
What about the hoses? Is just hose a hose right? On most modern filter the hose is nothing to worry about, but I have also had filters with weak hoses which will kink very easily. Highly flexible latex(ish) hose will kink way to easily. Kink = no water. The modern thick walled ones won't. Make sure you get the thick walled ones.

Hygiene
The filter design can help with keeping clean and dirty separated. Wrapping the dirty and clean water hoses together is a big No-No. This allows the dirty water droplets to come in contact with the clean hose. This will contaminate your clean water. This is not a big problem with non-biological threats, but with biological dangers, they can grow in quantity and become a hazard in your clean water supply. Especially in a warm wet bag.

I have seen a few solutions from manufactures:
- No clean water hose at all, just a tap (lots of Katadyn models)
- Attach directly to a water bottle/bladder, with a cover when the bottle is not attached (MSR)

I like the last one the most. Having just a tab means you have to somehow hold a bottle stable and pump at the same time.

Silver
Silver impregnation prevents bacteria from growing inside the filter. This a great feature specially for long term use. For short term use you can use a filter without, but it's best to pump some lightly chlorinated water to kill the bacteria, before frying and storing the filter.

Carbon element
Many filters are equipped with a carbon element. The carbon is used to absorb chemicals and other impurities. There solid carbon cores and the granulate versions. The granulate versions are more effective, but need to replaced regularly, after a certain amount of water or when a certain time has past.

So which one should you get?
Well that's up to you. If you buy a certified filter it should work, other then that. It's all personal preferences. If the filter is small, know that it takes a lot of labor to get it working.