The tube attached to the ballcock and discharging into the toilet tank is designed for what purpose?

• A. Replenish the water seal of the bowl trap
• B. Provide overflow protection
• C. Vent the tank
• D. Prevent backflow

Answer: (A)

The tube from the fill valve serves to restore the bowl’s water seal after a flush. When you flush, some water from the bowl is used up as part of the siphoning action, so a small amount of water is routed through that tube into the bowl to refill the bowl’s trap. This keeps the siphon seal intact, helping prevent sewer gases from entering and ensuring a proper flush on subsequent uses.

It isn’t for overflow protection, venting the tank, or backflow prevention. Overflow protection is handled by the tank’s overflow tube, venting is done by the building’s plumbing vent system, and backflow prevention relies on dedicated devices rather than this refill tube.