U-Shaped Underdrain Tubes
The U-shaped underdrain tubes for water and air distribution are low-pressure resistant, featuring a unique dual-layer water and air distribution structure with upper and lower layers. It consists of horizontal water and air distribution pipes (U-shaped underdrain tubes), vertical water distribution pipes, and vertical air distribution pipes. This structural design ensures that the uniformity of water and air distribution in the shutter filters is superior to other types of low-resistance air-water distribution systems. The inner and outer surfaces of the horizontal U-shaped underdrain tubes are smooth and flat, with wall thicknesses that meet requirements and are uniformly distributed. They exhibit good straightness and possess sufficient stiffness. During the initial installation of filter media or when the filter bed is empty for maintenance, the horizontal U-shaped underdrain tubes can withstand the pressure generated by the filter media and support layers above without any deformation or damage.
Product Overview
The U-shaped underdrain tubes for horizontal air-water distribution are bread-like in shape, and large hollow pipes having both sectional ends sealed. The tube crosssection is in circular shape at the top half and in square shape at the bottom half, with the top half section mainly serving as the air distribution space and the lower square section only as the water distribution space. Inlet openings for vertical water and air distribution pipes are provided at the tube bottom, while air-water distribution orifices on both sides of the tube, and air ventilation orifices at the top edge of the tube are provided. These openings and orifices at precise positions are able to guarantee uniform water and air distribution during filter backwash, and meet the requirements for cleaning the filter media. The air orifices ensure the formation of an air cushion layer inside the tube and enable uniform distribution of backwash air; the water orifices ensure uniform distribution of incoming and outgoing water. The spacing between the water distribution and air distribution orifices on the tube can be adjusted according to design requirements, with different orifice spacings configured for different flow rates through the orifices.
The vertical water distribution and air distribution pipes can be made of HDPE or stainless steel. The upper end of the vertical water distribution pipes extend into the horizontal U-shaped underdrain tubes by 20 mm. The upper ends of the vertical air distribution pipes are open and extend into the U-shaped underdrain tubes by 110 mm. The lower ends of the vertical air distribution pipes are sealed at the ends, but with four air inlet orifices, and an exhaust hole is opened at the top elevation of the top plate. The vertical water distribution pipes are not sealed at either end. The air distribution pipes have a circular opening at the upper end to create sufficient head loss, forming an air cushion layer in the U-shaped underdrain tubes to ensure uniform distribution of backwash air.
Scope Of Applications
Medium temperature: 0～+45℃
The U-shaped tube underdrain system is suitable for carbon filters/shutter filters in urban and industrial water supply, reclaimed water, and wastewater tertiary treatment projects. Work environment: Outdoor/indoor
Working medium: Water
Ambient temperature: Meets the meteorological conditions of customer sites
PH value: 5-9
Medium temperature: 0～+45℃
Specifications Table
| No. | Item | Technical Specifications |
| 1 | Length of U-shaped underdrain tubes | 3-6m (as per design drawings) |
| 2 | Cross-section Dimensions of U-shaped underdrain tubes | 136*170*5 (B*H*δ) |
| 3 | Water Distribution Orifice Diameter of U-shaped underdrain tubes | Ф13~Ф17mm |
| 4 | Air Distribution Orifice Diameter of U-shaped underdrain tubes | Ф3.5mm |
| 5 | Perforation ratio of U-shaped underdrain tubes | 1.2~1.4% |
| 6 | Backwash Head Loss | ≤200mm |
| 7 | Vertical Water Distribution Pipe | DN80L = 1080mm (or as per design) |
| 8 | Vertical Air Distribution Pipe | DN30L = 690mm (or as per design) |
| 9 | Material of U-shaped underdrain tubes | HDPE or Stainless Steel |
| 10 | Material of Vertical Distribution Pipes | HDPE or Stainless Steel |
Technical Specifications
Horizontal U-shaped underdrain tubes:
① Cross-sectional dimensions:
Upper section: 70 mm inner diameter semi-circular tube;
Lower section: internal dimensions width × height = 136 × 110 mm rectangular tube.
② Length: Determined based on filter bed dimensions.
③ Material: HDPE, stainless steel.
Vertical water distribution and air distribution pipes: Determined based on design.
