Recently I was introduced to home made anti-siphoning device. I use a Mag 18/SCWD to return my water to my tank from my sump. I recently removed my anti-siphon valve to due to decrease of flow. I wanted more flow man! The downfall was that I would have water return to sump because I had nothing to stop it. I did not want to decrease flow. I had a problem until a friend invented this for me. He took some air line tubing and placed it into each return nozzle. He connected air line tubing to each nozzle in series first. Then he cut it in two. He put a t insert in the middle, then attached another T insert to allow my prefilter to be connected. When the pump is turned on it sprays water out the open t insert . When water is turned off air is sucked into T insert breaking the vacuum. It was very cheap and very effective. All you need are air line tubing and two plastic T inserts to connect return spray nozzles to prefilter. I hope this helps someone like it did me? I have my increased return pressure and also an anti siphoning device.