3701-31-04 (B)(6)(c)(ii) / Backwash lines and lines from drainage sumps have an air gap and are open to freely drain
Backwash lines and lines from drainage sumps did not have an air gap prior to discharge
Open the lines that discharge into the backwash or drainage sumps so that there is an air gap and the lines can drain freely. PROVIDE AN AIR GAP FOR THE FILTER BACK WASH DISCHARGE LINE.