My overflow has recently started making some loud gurgling and "flushing" noises. I have a Durso standpipe in place and haven't had any problems for the past year or so. The input to the sump from the overflow has only a slight bend and ends about 1 inch below the surface of the water in a bubble tower filled with LR rubble.
The noise is not constant (thank the reef gods!) but usually happens every night around 3am. Great timing.
Any thoughts other than throwing it across the room?
