The Durso standpipe is used to quiet the flow from a noisy over flow box. In some cases water in an overflow falls over two feet. This makes plenty of noise as it splashes down. The water then sucks in plenty of air making obnoxious gurgling moises as it drains to the sump. The Durso standpipe reduces this noise by raising the water level and limiting the amount of air that is sucked into the drain.
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