Hayward VLX4001A Standpipe and Underdrain Assembly

What This Part Is Used For
The Hayward VLX4001A is a standpipe and underdrain assembly used inside compatible Hayward VL Series sand filters. It manages internal water distribution through the sand bed and supports proper filtration and backwashing. This assembly lives inside the filter tank under the multiport valve connection.

Why This Part Matters
If the internal underdrain components are cracked or out of position, the filter can bypass sand and return debris to the pool. That leads to cloudy water and frustrating cleanup after service. Replacing damaged internals restores proper flow through the sand bed and consistent filtration. Correct internal fitment also supports effective backwashing and longer filter runs.

Key Features and Specifications

• Manufacturer part number: VLX4001A
• Standpipe and underdrain assembly for compatible Hayward VL Series sand filters
• Internal component that supports filtration and backwash flow paths
• Installs inside the filter tank beneath the valve connection
• Used when internal components are damaged or bypassing

Installation and Fitment Guidance
Service the filter with the system off and fully depressurized, then remove the valve to access internal components. Ensure all internal parts are seated correctly before adding sand or reassembling. Confirm by manufacturer part number before ordering.

About the Hayward Brand
Hayward manufactures a complete residential pool equipment ecosystem including pumps, filters, heaters, automation, cleaners, chlorination products, and service parts. Their sand filters and internal components are built to integrate with Hayward valves and pumps on common equipment pads. This compatibility simplifies long term maintenance and repairs. Hayward service parts are widely supported across residential pools.

Common Service Context
Techs typically replace underdrain assemblies after freeze damage, broken internals found during a sand change, or when the pool returns sand or debris after backwashing. It is often recognized when water clarity will not improve despite proper chemistry and filter pressure readings.