Was wondering why my chlorine kept going down. My Stenner is moving... then at closer look (5 days later), it's moving but level in tank hasn't moved. Disconnected output and nothing dripping... I had one extra tube and replaced it, now all seems to be working well. What is the expected life of the tube? It's been about a year and a half, old tube "seems" OK but is kind of mashed, so maybe nothing or very little getting through. Just curious about expected maintenance. Going to order a 5 pack from ChemWorld (best price with shipping). One of the rollers is also a bit tight, but rotates. Other 2 rotate freely.