A running toilet wastes hundreds of gallons of water per day and adds $50 to $100 to your monthly water bill. A weak flush means clogs and repeated flushing. A leak at the base means water damage to your subfloor. All three problems are fixable by a homeowner with basic tools and $10 to $30 in parts.

Toilet Repair Guide

Problem 1: Toilet Runs Constantly

A running toilet almost always means water is leaking from the tank into the bowl through the flush valve. This triggers the fill valve to keep refilling the tank.

Check the Flapper

The flapper is the rubber disc that seals the flush valve at the bottom of the tank. It lifts when you flush and drops back down to seal the tank.

Remove the tank lid and look at the flapper
Push it down gently with your finger — if the running stops, the flapper is not sealing
Check the flapper for warping, mineral buildup, or deterioration (it should be soft and flexible, not stiff or rough)
If worn, unhook the flapper from the flush valve pegs, take it to the hardware store, and buy a match
Hook the new flapper on, connect the chain to the flush handle lever, and test

Flapper replacement takes five minutes and costs $3 to $8. It solves running-toilet problems about 80 percent of the time.

Adjust the Chain

If the chain connecting the flapper to the flush handle is too short, it holds the flapper partially open. If it is too long, it can get caught under the flapper. Adjust so there is about 1/2 inch of slack.

Check the Fill Valve

If the flapper is fine, the fill valve may be the problem. The fill valve controls water flow into the tank. If it does not shut off when the tank is full, water overflows into the overflow tube and runs continuously.

Check if water is flowing into the overflow tube — if yes, the fill valve is not shutting off
Adjust the float (a ball or cylinder on the fill valve) lower to reduce the water level
If adjustment does not help, replace the fill valve. Universal replacement valves (Fluidmaster 400A) cost $8 to $12 and install in 15 minutes

Problem 2: Weak or Incomplete Flush

Check the Water Level

The tank water level should be about 1 inch below the top of the overflow tube. If it is lower, the flush lacks power. Adjust the float on the fill valve to raise the water level.

Clean the Rim Holes

Water enters the bowl through small holes under the rim. Mineral deposits can clog these holes, reducing flush power. Use a mirror to look under the rim, then clear each hole with a piece of wire or a small Allen key. Soak stubborn deposits with vinegar overnight.

Check the Flapper Drop Speed

If the flapper drops too quickly, it cuts off the water flow before the tank empties fully. Adjust the chain length or replace the flapper with one designed for your toilet model.

Problem 3: Toilet Leaks at the Base

Water pooling around the base of the toilet usually means the wax ring seal between the toilet and the floor flange has failed.

Turn off the water supply valve behind the toilet
Flush the toilet and hold the handle down to drain as much water as possible
Sponge out remaining water from the tank and bowl
Disconnect the water supply line
Remove the two bolts securing the toilet to the floor (they may be under decorative caps)
Lift the toilet straight up and set it on its side on an old towel
Scrape the old wax ring from the toilet base and the floor flange
Press a new wax ring onto the toilet outlet (warm the ring in your hands first for better adhesion)
Lower the toilet onto the flange bolts, pressing down firmly to compress the wax ring
Reinstall the bolts, connect the water supply, and test

Do not over-tighten the floor bolts — porcelain cracks easily. Alternate between bolts, tightening a little at a time until the toilet does not rock.

Problem 4: Toilet Rocks or Is Loose

A rocking toilet will eventually break the wax ring seal and leak. Fix it by:

Tightening the floor bolts gently
If the toilet still rocks, the floor is uneven. Insert plastic toilet shims under the base where the gap exists, then caulk around the base with silicone to lock the shims in place

Tools and Supplies

Adjustable wrench and pliers
Sponge and bucket
Replacement flapper, fill valve, or wax ring as needed
Plastic toilet shims
Silicone caulk

When to Replace the Toilet

Consider replacement if:

The porcelain is cracked (cannot be repaired)
The toilet requires frequent repairs
It uses more than 1.6 gallons per flush (older models use 3.5 to 7 gallons)
You want to upgrade to a water-efficient model

A new toilet costs $100 to $300 and installation is essentially the same process as replacing a wax ring — you are already familiar with the steps.