Toilet Won't Suck the Water Down

How a Toilet Works

The design of a toilet bowl allows water to enter it quickly from the tank when you flush it. As the water level in the bowl rises, it overflows the internal S-trap of the toilet and begins to fall down the waste line. Because it happens quickly, the water seals the waste line and creates a suction behind it that empties the bowl. When the bowl stops filling, the water level subsides and air eventually gets sucked into the waste line and breaks the vacuum. It creates the characteristic gurgling sound you hear at the end of a flush cycle.

When water doesn't flow fast enough to create suction, the first place to check is inside the tank. The flapper, which is the rubber cover over the siphon hole in the bottom of the tank, may not be lifting up all the way when you flush. The chain may be too long or there may be something in the way. If it doesn't lift, the hole doesn't open wide enough to allow the flow necessary for suction, and the flapper can fall down before the flush is complete, inhibiting the flush sequence even more.

If your toilet is old, obstructions from mineral deposits may have developed in the passage between the tank and the bowl or in the outlet holes around the rim of the bowl. They can impede water flow and suction. There may also be an obstruction in the waste pipe or the S-trap of the bowl. It can limit water flow out of the bowl so that there isn't enough to fill the waste line. For example, a tampon may be lodged in the S-trap. To get the toilet working again, you'll have to remove it somehow.

Early versions of low-flow toilets were notorious for requiring more than one flush, defeating their purpose as water-saving devices. They didn't release enough water at once for an efficient flush and weren't always compatible with the existing waste line configurations. The design of low-flow toilets has been improved since they were first introduced and contemporary ones seldom require more than one flush. There isn't an easy way to modify a low-flow toilet that isn't flushing well. If you suspect yours isn't functioning properly, the best course of action is probably to replace it with a newer one.