Pentair T40BG AutoFill Automatic Water Filler with Side-Mounted Float Valve (Gray)

The Pentair T40BG AutoFill is an in-deck automatic water leveler designed to maintain a consistent pool or spa water level using a simple, reliable float mechanism (no electronic controls). When the water level drops below your set point, the float valve opens to add water until the proper level is restored. If the level rises too high, the built-in overflow helps remove excess water to reduce overfilling and water waste.

Key Features

• Automatic water level control: Helps keep water at a steady operating level for reliable skimming and circulation.
• Side-mounted float valve: Mechanical float design meters in water as needed without electronics.
• Built-in overflow: Helps protect against overfilling and related water waste.
• Compact housing: Approximately 7" diameter deck canister fits many new builds and renovations.
• Durable construction: Corrosion- and chemical-resistant ABS polymer body designed for outdoor pool environments.
• Color: Gray lid/ring (T40BG).

Common Applications

• In-ground pools and spas where maintaining a consistent water level protects equipment and improves day-to-day operation
• New construction and remodels requiring a compact in-deck autofill canister
• Installations where a non-electronic, mechanical water leveler is preferred

How It Works

• As the pool water level drops, the float lowers and opens the fill valve to add make-up water.
• Once the set level is reached, the float rises and closes the valve to stop filling.
• If water rises above the normal level, the overflow pathway helps carry away excess water.

When to Replace

• Water level no longer holds steady (valve won’t open/close consistently)
• Continuous filling or frequent overfilling
• Cracked canister, damaged lid, or worn internal float/valve components
• Sticking float or debris-related valve issues that return soon after cleaning

Installation Notes

• Confirm your desired set waterline height and orient the side-mounted float so it moves freely without contacting the canister walls.
• Use a proper backflow prevention method per local code on the water supply line to the autofill.
• After installation, test fill shutoff and overflow operation before leaving the system unattended.

Maintenance Tip

Periodically remove the lid and check for debris, scale, or insects that can restrict float movement. If you notice the pool filling more than usual, inspect for leaks in the pool system and verify the float valve is sealing fully when the target level is reached.

Related Products (Aqua Pool Supply)

• Pentair AutoFill replacement parts
• AutoFill float valves
• AutoFill lids and rings
• Pool backflow preventers
• Automatic pool water levelers