As with any mechanical system, there are a variety of service issues that come up for solar hot water. One of the most common are failed air vents. These devices are prone to failure no matter where in a piping system they are, but the roof is a particularly challenging environment for them. Ostensibly they are installed to let air out when charging the system with glycol, however, with the right equipment and techniques, one can persuade all of the air to come down to the basement. This is why when we address this issue, we simply remove the air vent and put in a plug.