The SteriPEN uses four AA cell batteries. While any AA batteries work, tests have shown that high quality Lithium batteries provide on average ten times the treatments of standard Alkaline batteries.
So if your low battery indicator is flashing and you've recently replaced the batteries try using Lithium or NiMH batteries instead of Alkaline.
2. Testing your SteriPEN.
If you attempt to test your SteriPEN in tap water you will often find that it does not work. This is because tap water is considerably purer than water from a stream or river, and lacks the sediments and minerals found in nature. The SteriPEN water sensors use the sediment in the water to detect it and therefore will not activate in tap water. Try stirring in a teaspoon of salt or sugar before testing your SteriPEN.
3. Low Temperatures.
Battery performance may be adversely affected by cold weather, try to ensure your SteriPEN is above 0°C before use. Store your batteries in your pocket or in a warm place in cold weather.
4. Sensor not dry problems.
If the water sensing pins are dirty or wet they will be unable to detect water, and the flashing green LED will not activate. Clean and dry the water sensors with a clean cloth to prevent this problem from occurring.
5. Turbid, murky or cloudy water.
SteriPEN is intended for use, and is most effective, in clear water. However, SteriPEN has been shown to reduce contamination in cloudy water. If clear water is not available, first try to filter the water to clarify it. If it is necessary to treat turbid, murky or cloudy water then use double the normal dose. For example, to treat one litre of turbid water, use two one-litre treatments.
Note: treating turbid, unfiltered water should only be done when clear water is unavailable. Use clear water whenever possible.
6. Alternative treatment.
As with any water treatment systems, you should always have a backup method of water treatment available.