A filter nozzle is a nozzle with a filtration design by which the media is retained and provides a good distribution of water and air.
Use of filter nozzles
Filter nozzles can be installed in side pipes or on suspended floors. The nozzle has three main components, a filter for removing media or filling with gravel, a water control orifice, and a tail pipe with an orifice for controlling airflow. The nozzle may rely on the open area of the filter slot to provide controlled head loss for good distribution, or a separate orifice within the assembly is often preferred. The filter slots may be partially clogged with media. This will change the head loss of the slot. If the control orifice is within the nozzle body and the slot has a large open area, a partially clogged slot will have less effect on the head loss through the nozzle.
Filter nozzle slot sizes vary widely from approximately 0.2 mm to 10 mm, with larger slots most suitable for upflow filters. Slots of 0.2, 0.3, and 0.35 mm are typically used for direct contact with the filter media without needing a gravel layer on top of the nozzle. This direct contact facilitates a combination of air flushing and water backwashing.
If slots less than 1.0 mm wide are to be used, care must be taken to avoid the entry of grit with the backwash water. If the filtrate is always used for backwashing, there is usually no problem. Some flooring suppliers market nozzle-free floors, but these rely on filler layers or porous compositions that seem to clog equally or more quickly and are more difficult to clean.
The filter nozzle tailpipe serves to control the distribution of air. If air is not used, an exhaust tube is not required. The tailpipe usually has an upper orifice (starter or vent) and a lower orifice or slot (metering orifice/slot). When air is applied to the floor, suspended or lateral, the air collects under the floor and presses water down until the air reaches the metering orifice or slot. The metering orifice is sized accordingly to prevent air from reaching the end of the tailpipe, which would result in poor air flush distribution and localized intense aeration, which in turn would result in uneven media, possibly carrying media into the discharge channel and mixing the filter media layers (if used).
Filter nozzles can be made from various materials, such as plastic and metal, and are supplied with auxiliary components for installation in concrete, sheet metal floors, and lateral pipe systems.
If you would like to customize or purchase high-quality filter nozzles, please contact nozzle manufacturer CY Spray.