Hi Bill!
I've pretty well had it with filters because the constant vibration of the rough roads I ride seems to crack the ceramic filter elements, and some seemed to clog prematurely no matter how carefully I pre-filtered the water.
Instead, I switched some time ago to a SteriPen Classic UV water purifier. SteriPen's CR123R (rechargeable form of the CR123 battery; pretty difficult to find in rural areas in my neck of the woods) model is more compact, but not so easily charged by my Tout Terrain The Plug2+, B&M e-Werks or Joos solar panels, which do a nice job refilling my Eneloop AA cells through an Eneloop USB charger.
The SteriPen is not the lightest purification device, but it is one of the fastest by volume. I take chlorine and iodide pills as a backup and can also boil water, but for the fastest clean water, I've found nothing to beat a SteriPen, and it is impervious to clogging. To save weight, one can "rob" batteries from other gadgets to operate it, then recharge and restore the piles to the other devices after water chores are done. For my use, it is worthwhile to keep a set of fully charged Eneloop XX piles in the purifier so it is always ready to go and can be depended on for continued use when needed.
I always carry 6.5liters of water on the bike itself when desert touring, and usually boost that to 8l for an average day's *drinking* intake in desert heat. Cooking my dehydrated food requires more. In the hot season, I also pack two 10l MSR Dromedary bags, for a total water capacity of 26.5 to 28l to see me through 4-5 days without resupply. Given the volume, being able to purify water quickly by the liter every 3 minutes or so makes a big difference as I'm sitting in the hot sun refilling my water tanks. On the alpine and forest transits from my home in the Valley up over mountain passes to high desert plateaux, I can count on finding water in streams. Much of it is infected with various blastocysts (i.e. giardia) and some sources have water-borne hepatitis, but being able to zap-and-go quickly means I can carry less water *and* keep my average speed faster than if I had to wait 30+ minutes for chemicals to become fully effective in cold water or if I had to pump or wait for a gravity-fed (water bag) filter. This makes my SteriPen Classic the lightweight choice for my style of riding but it might not work as well for other locales.
I do have to be careful with the SteriPen in several circumstances:
I pack it with the cover on in a neoprene sleeve so it is unlikely the UV bulb elements will break.
I make sure I have fully charged high-capacity batteries on hand for it. The thing sucks alkaline disposables dry after just a couple uses, but has so far done very well for me using the high-capacity Eneloop XX cells. That's why I prefer to have a set dedicated just to the SteriPen. If I expect heavy use, I put the cells in the charger right after use so they'll be fully topped up if I need to purify more water in a few more hours.
If water is unusually pure and lacks much in the way of native mineral content, I add a pinch of salt so the SteriPen contacts can make contact to start the UV light going.
So far as I can tell, the SteriPen does nothing to alter the taste or color or smell of the water. The result is not always palatable, but I have not gotten sick after using it on some pretty sketchy water. Hold your nose, take a drink, and you're hydrated; mission accomplished.
The SteriPen's indicator light is hard to see in bright sunlight, but critical. For this reason I have standardized on opaque black water bottles (Zιfal Magnum 1l) so I can actually see the UV bulb glow, nevermind the indicator light.
As with any form of purification, it is critical to avoid cross-contamination. For dipping from crevices and toilet tanks, I use my silicone measuring/drinking cup, which is then disinfected afterward. The water is then dumped into the water bottle, being careful to avoid spillage onto the lid threads with the cap well away from the splash zone. The water is then zapped and the last step is to slosh some purified water over the threads before capping. I do the same with boiled or chemically treated water so the clean water and container are not cross-contaminated by the dirty water.
If water is unusually turbid or dirty, I clear it in several ways so the SteriPen can zap effectively: By spin-swirling the bottle (crude centrifuge) so contaminants are thrown to the bottom and I can decant clearer water from the scoop container to the purification container, let it settle with time (a few minutes), or filter it through some pantyhose (ladies tights) which *always* go on my tours (cut off the trunk and they make sun sleeves, substitute for broken cargo straps, can be soaked in insect repellent and then donned, or used as a water filter, to keep produce together in my panniers,worn when cold, plus about a million other uses including as mouth and nose filters in dust storms for my desert travels). They are especially useful for skimming off algae from (cattle) stock tanks and livestock ponds. Though it may not always taste good, water contaminated by cattle urine and feces is safe to drink after the SteriPen has zapped it -- provided it is clear enough for the light to fully contact the (cleared) water. I'll sometimes zap it twice, all while swirling the bottle for the 90 seconds it takes to purify 1 liter.
No filter will correct for alkali contamination in water, so I check my sources first by dipping a pH test strip in the water before attempting to zap it. If there is too much alkali, then I rely a bit longer on my reserves until I can find a more likely source. There is usually enough blowing alkali dust in the air to raise sores on my lips and around my nostrils (you can see an example here:
https://www.youtube.com/watch?v=AISuUrSM74Q ), so I wouldn't relish drinking the stuff; it can scorch through and damage mucous membranes, not a good thing on tour.
I have no connection to the company and bought my own, finding success with the SteriPen Classic after some frustrating times with various filters and pumps. The Classic can be found for a pretty low price at season-end sales -- sometimes as little as USD$35-38 here in the States (what I paid, about £23-£26 *plus* shipping, which could add a good bit if sent to the UK). People generally avoid it in favor of the more expensive, more compact models, but I deliberately chose it for the AA cells.
Hopefully helpful as another data point to consider.
Best,
Dan.
