WINDOW PERFORMANCE The Learning Center Under actual field conditions, a water head will build up to balance the pressure exerted on the window. The higher the pressure the window sees, the higher the height of the water head. With any type of operable window, the water is forced through the unit by pressure and a variety of other mechanisms. This is true regardless of style. However, because half the interior track is visible from the inside in a sliding window, the balancing water head is visible. Water will build up in the inside track of the window until the height of the water creates a water head to balance the outside pressure. As the air pressure, or wind velocity, rises and falls, so does the height of the water seen in the sill track. With any window, under extreme high wind and heavy rain conditions, there even may be enough pressure to force the water over the inside of the sill. Under typical wind and rain conditions, water may find its way into the inside track of a sliding window. The amount that can be seen will be dependent upon the pressure being exerted on the weep holes or covers. Unless the wind becomes extremely high, the water head will eventually exceed the air pressure, forcing the water through the drain holes in the track and out the weep holes in the sill. In any standard sliding window, some water may be seen in the inside sill track when significant wind pressure is exerted on the window. Some residual water, or water droplets, may even be left on the bottom of the track after the pressure has been removed. In a typical slider, the inside track leg is designed so that it is high enough to hold the expected water head, while the drain system is designed to remove the bulk of the water once the air pressure drops. Since this water will drain out over time as the air pressure decreases, water in the sill track is not detrimental to the performance of the product unless it overflows the sill and comes past the inside surface of the window frame. 6. What causes the visible water in the sill track of my new windows? < back to list of questions about window performance 1-877-SWING CLEAN info@energyswingwindows.com 3245 Miracle Drive Murrysville, PA 15668 724-387-2991 PA Contractor ID PA001856