http://www.waterfilters.net/Reverse-Osmosis-Filter-Systems.html Aquaman explains how to troubleshoot and fix the two most common problems with RO systems. As reverse osmosis systems age, the reservoir tanks wear out and the bladder inside the tank fails causing the symptom of no water delivered to the faucet. Checking the pressure on the tank is easy and necessary to determine if the tank is still in good condition. ASO (automatic shut off) valve failure is another common issue with under sink RO systems. The symptom is continuous flow of water down the drain. Both issues are easy to verify and repair. Follow Aquaman’s advice and you can inexpensively troubleshoot and repair your reverse osmosis drinking water filter system. Aquaman is a Water Quality Association Certified Water Specialist. His training and experience have given him a deep understanding of water chemistry and water purification equipment. This enables him to provide scientifically accurate information that you can trust!