Here is a manual backwash valve head for a 4" FRP vessel with a flow rate of 10,000 LPH:
 
Manual Backwash Valve Head Manual
 
The Manual Backwash Valve Head is designed for use with 4" FRP vessels and is suitable for various filtration media such as Activated Carbon, Silica Sand, Birm, Iron Removal Resin, Crystal Sand or AFM Glass Media. This manual backwash valve allows for easy and convenient cleaning of the filter vessel by manually backwashing out sediment, dirt, rust, and other large particles that are caught between the media granules.
 
Specifications:
Inlet: 2"/ 50mm female
Outlet: 2"/ 50mm female
Drain: 1.5"/ 40mm female
Base Thread: 4"/ 10.16cm
 
Installation Instructions:
1. Ensure the valve head is installed in a vertical position.
2. Connect the inlet and outlet pipes to the valve head according to the manufacturer's instructions.
3. Connect the drain pipe to the valve head.
4. Tighten all connections securely to prevent leaks.
 
Operation:
1. Close the valve head by turning the handle clockwise.
2. Open the drain valve by turning it counterclockwise.
3. Allow the water to drain completely before opening the inlet valve.
4. Open the inlet valve by turning it counterclockwise.
5. Close the drain valve by turning it clockwise.
6. Open and close the valve head several times to rinse out any remaining debris.
 
Maintenance:
Regularly inspect the valve head and replace any worn or damaged parts.
Clean the valve head and surrounding area regularly to prevent mineral buildup and corrosion.
Lubricate moving parts regularly to prevent sticking.
 
Troubleshooting:
If the valve head is difficult to turn, check for mineral buildup and clean as necessary.
If the drain valve does not open or close properly, check for blockages or damage and replace as necessary.
 
Safety Precautions:
Always follow proper safety procedures when handling the valve head, including wearing personal protective equipment (PPE) such as gloves and safety glasses.
 Ensure the valve head is installed and operated within its rated specifications to avoid damage or injury.
Avoid exposing children or pets to the valve head or its components.