Demystifying the drainage debate
As a whole, the window industry has never truly understood the issues surrounding water damage and window drainage. Many misconceptions still exist regarding how to best handle drainage issues.

Myth #1:
A horizontal slider that tilts in for cleaning is a worst-case scenario for water drainage.
Most of the window industry believes that in order to achieve good water test results, you have to compromise air performance. This is inaccurate, yet is still widely accepted as fact because water that leaks into a window has to be redirected outside. This requires that holes be cut into a window so that water can be released. But these holes also allow air in – and the more holes there are, the worse the air performance is.

The Preferred development team has engineered a product that alleviates this problem. Their HI-FLO drainage system maximizes the flow rate that results from the low pressures found in window and sliding door sills. The system is specially engineered to give optimal flow rates and drainage performance, even when working on a 45º angle.

Our one-way valve weeper assembly snaps on right over the hole. This prevents air from being pushed into the window, while allowing water to be pushed out. Other companies sell what they call ‘weep covers’, but they’re merely little hoods that cover a hole and make it invisible – but have no valves on the covers.

Myth #2:
It takes magic to pass the water test.
The standard water test is graded by pressure – one-tenth of the structural pressure of a window. That means for Level 20 (30 lbs./ft2 structural), a window would have to pass the water test at 3 lbs/ft2 of pressure. When water leaks into the window, it accumulates in the sill until it builds up enough pressure to open the one-way valve. Therefore, there must be more pressure inside the sill than exerted on the exterior of the window by external forces like wind.

By merely factoring the density of the water at 62.5 lbs./ft. and multiplying it by the height of a window sill, manufacturers can determine how high their sill needs to be in order to overcome outside wind pressure. “If you have proper drain holes, channeled in the right way, you will ensure that your window passes the water test. There’s really no magic involved – it’s just regular old physics.”

When a window is tested, the amount of water sprayed on it is quite excessive (twice as much pressure as ever recorded in North America). Not surprisingly, this causes water to leak in, because all windows will leak to a certain extent. But that water has to be channeled back out – and it has to drain out at least as quickly as it’s coming in – or it’s going to start backing up. Preferred’s HI-FLO Weepers were designed with this in mind.

After calculating the flow rate and pressure required, we determined what size opening was needed to allow the same amount of water coming in to be drained out. If you have a tiny hole and you want the water to exit at a certain speed, more pressure needs to be applied. When you have a bigger hole, more water can be drained at less pressure. Our HI-FLO drainage system was engineered so that water could flow out under low pressure.”

Hanging drainage myths out to dry
HI-FLO Weepers enable manufacturers to produce windows with a built-in, high-capacity drainage system. Molded from non-hydroscopic material, the HI-FLO reed valve (one-way valve) is designed to work in the low-pressure environments of window and door sills, while not retaining moisture. The valve remains closed, preventing air and insects from entering the home until interior water pressure (caused by water infiltration), exceeds the exterior wind pressure and allows water to escape. Additionally, an integrated hood covers the reed valve and protects it from being shut by water streaming down the face to the window.

Innovative products like the HI-FLO drainage system are evaporating old drainage myths and giving window manufacturers the opportunity to minimize water damage and costly service repairs, without sacrificing air performance for water performance. The company’s philosophy this way: “We’re a product development company first, and a manufacturer second. We supply on time and make a quality product, but we’re always developing something new. We’re always looking to make new and better products and improve on what the industry considers standard.”