Pond Boss Forums AERATION Systems questions Check valves

The center of the bladder has no slits and uses the force of the water down pressure on the bladder to act as the check valve along with the rebound memory of the bladder itself.The hole in the center of the disc varies from manufacturer and intended use. Some manufactures will use an orifice size that keeps constant pressure to the underside of the disc so that if the disc isn't perfectly level on the pond bottom it will still have the same flow high side and low side. This is also another reason not to operate a disc above the suggested cfm rating as these bladders can stretch and compromise the check valve effect. Some bladders have I slits some C slits, some have the slits arranged in a delta pattern, some have a proprietary rubber composition that gives better "rebound memory" but to look at them they can all look similar ! Hope this helps.