I drilled a small hole right at the water line of the bog so if I lose power the air is sucked in and it stops the reverse flow after some water drains back in the pond. You will most certainly want a full bore sized valve for the back flush. It may not back flush at first because there isn't much resistance. After a while the build up will start and once you open the valve some yucky will come out until it runs clear. One more thing, be sure and try and stay away from aggressive growing plants like pickerel rush, horse tail, mint, and water celery. They all do a great job the first year but after a couple of years of growing they are a pain to thin out.