Toilet flush is weak or won't flush all the way

Question 1: Lift the tank lid. Where does the water stop after the tank refills?

The overflow tube is the open pipe standing in the middle of the tank.

• Well below the top of the overflow tube: Likely cause: not enough water in the tank
• About 1/2 inch to 1 inch below the top of it: go to question 2

Question 2: Press the handle and watch the flapper. What does it do?

• It barely lifts, or the chain hangs very slack: Likely cause: a chain that is too loose
• It lifts but drops shut before the tank empties: Likely cause: a flapper that closes too soon, or the wrong size
• It lifts fully and stays up until the tank empties: go to question 3

Question 3: Is the small refill tube clipped into the top of the overflow tube?

It is the thin flexible tube running from the fill valve. During refill it should spray into the overflow tube.

• No, it has fallen off or sprays outside the tube: Likely cause: the refill tube has come loose
• Yes, it is clipped in: go to question 4

Question 4: Hold a small mirror under the bowl rim and flush. Does water come out of the rim holes evenly all the way around?

• No, some holes barely flow or look crusted: Likely cause: mineral buildup in the rim holes
• Yes, it flows evenly: go to question 5

Question 5: Do other drains in the house run slowly or gurgle too?

• Yes, other fixtures are slow too: Likely cause: a drain or sewer line restriction
• No, just this toilet: Likely cause: a partial clog in the toilet trap