I've had this filter for a few years and I had never used it after my first use until this past weekend. First use was on a backpacking trip to the High Uintas, we camped by a lake with what I considered very clean water. The original filter lasted around 24 hours, as others have stated. We had a large group and this was meant to be our large supply of water, not the case. With no visible debri or dirt, the filter was inoperable very quickly. Fortunately, we had alternative pump options to get us through the trip. After returning from the trip, I contacted Katadyn and I was told they had issues with a batch of filters and that they'd send me a replacement. NEver touched it again until a yurt trip this past weekend. We used melted snow as our water supply and the filter worked well upon its first fill. Round 2, not so much. The filter immediately stopped worked upon my second fill and it was time to troubleshoot. Again, the water being filtered appeared very clean but I couldn't get a drip out of the hose, even when sucking on the hose, I could not pull water through the filter. What I found was there's a small grey tab (circled in the attached photo) where the hose connects to the bag, I removed the hose, drained the water out of the hose and reconnected the connector and the filter immediately worked again. There was no clog and no debri so I do not know what the issue was but the filter worked for the remainder of our trip. When it works, it works great, water flows pretty quickly and I am confident it's coming out clean. However, I have lost confidence in the filter and I would not rely on this product as my sole source of drinking water. Bring a backup or buy something else.