How to Clean Toilet Tank Anti-Siphon Valves

Shut off the water supply to the toilet by turning the fill valve handle to the right as far as it will go.

Remove the top to the toilet tank. Set it on a towel or rug to protect it from cracking or chipping.

Locate the short arm at the top of the anti-siphon fill valve. Unlock the cap on top of the anti-siphon fill valve by lifting the arm and turning it so it faces the wall behind the toilet.

Hold the fill valve cap open with one hand. Reach down behind the toilet and turn the water supply back on by turning the handle to the left. Allow water to run through the anti-siphon fill valve for 10 seconds to flush debris and sediment from the valve system.

Turn the water back off and set the cap down for a moment. Pour white vinegar over an old toothbrush. Lift the anti-siphon fill valve cap again and scrub around the black rubber seal with the vinegar-dampened toothbrush to remove scum, mildew and debris. Wipe the seal with a clean cloth.

Place the anti-siphon fill valve cap back down. Turn the short arm at the top toward you until it's back in a locked position.

Fill the toilet tank by turning the water shut-off valve to the left so the water supply is on again. Replace the toilet tank lid onto the top of the toilet tank.