except to tell you that the plastic water bottle is constructed of poly carbonate(which has been declared to be toxic by several industrialized nations), it is not fair to myself, the vendor, the manufacturer, or to amazon, to offer up a review until i finish my "field trial"..

i purchased the steripen system for an upcoming trip to mexico, and i cannot, in good conscious, offer up a review until i return..

at this time, i would suggest that you purchase only the pen(without the polycarbonate bottle).. i have disposed of the bottle and will be using only the pen while in mexico.. after all, i bought the "system" to get rid of toxic material..

beleive you me, when i get back, i will let you know what i think..

hasta la vista
j

you have to press the button first, wait for the green light, then immerse the light tube into the water. Great for traveling to another country where the water condition is unknown.. and yah.. NIMH battery is a must or else you will be running through the alkaline batteries like there is no tomorrow... too bad they didn't provide it.

Took my SteriPEN for 8 days in the Smoky Mountains. It worked every time and must have done the job because there were no ill effects. Do use lithium batteries however.

For anyone having problems I found this at http://www.backpackgeartest.org/reviews/Water%20Treatment/Ultraviolet/SteriPen/Owner%20Review%20by%20John%20Heubi/

I was able to determine that the extended outdoor use seemed to create too much humidity within the unit and caused this malfunction. The malfunction occurred with a much greater frequency during periods of extremely high humidity and periods of extended rain. I was able to "fool" the unit when I got a red light by waiting for the indicator light to stop blinking and then placing the unit in the water, just as if I were purifying the water. Then I would pull it out of the water, just as if I had completed the purification, then push the button again. The SteriPEN would then work just fine for any number of uses. I am certain that this would not even be an issue to anyone using the SteriPEN for weekend or week long treks. The problem also goes away after the unit is in a controlled environment (inside) for approximately 1-3 days to get a chance to get completely dried out.

I was out on the trail for four days. This was my only water purification system and it worked great for three days. The pre-filter was fantastic. It collected things I couldn't even see, leaving a brown film on the screen. The SteriPEN is supposed to give a green light when complete. On the fourth day I started getting red lights. The UV light came on for 5 seconds and then shut off giving a red light. The batteries were brand new. I took the batteries out and then put them back in. I dried the unit off. I dumped the water out and put new water in... Red light, red light, red light. I got on the trail an hour late that day and probably ended up drinking some non-purified water. I cannot recommend this product.

The product did perform as describe. I order two sets of the Lithium Ion battery from another source, one set worked and the other did not.
After a week of constant use, about 6 times a day, it needed a new set of battery. Rechargeable NiMH battery also worked in the unit.

I purchased the combination set with the bottle and pre-filter. The main advantage is the fileter adapter allows the SteriPEN to be inserted into the bottle and form a water tight connection. This makes it easier to shake or swire the bottle without worrying about spilled water.

It took me a while to figure out what was the sediment filter. I thought at first it was missing, but it was the funny thing sticking out the middle of the adapter. Removing the filter from the adapter allows the SteriPEN to be tightly inserted into the bottle. For most purposes, the filter serves no useful purpose, so I just put it away for safe keeping.

I used the unit to purified all my drinking water in Inner Mongolia and any water used to brush my teeth in any hotels in China. At the Beijing Airport, when leaving the country, it did raise some concern about what the device was, and added an extra step to the out processing when they attached a photo of me with a x-ray picture of the unit.

I will take the unit on my next back packing trip to truely purify my drinking water. I have never been sick from just using a water filter on previous trip, but this unit is convenient.