What's actually causing this
Toilets run when water continuously trickles from the tank into the bowl. The two most common culprits are a worn-out flapper that doesn't seal properly, and a fill valve that's stuck open or set too high.
What you'll need
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- Toilet flapper kit Shop →
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Step-by-step fix
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1
Diagnose the problem
Lift the tank lid and add a few drops of food coloring. If color appears in the bowl within 10 minutes without flushing, the flapper is leaking.
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2
Turn off the water supply
Turn the shutoff valve behind the toilet clockwise. Flush once to empty the tank.
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3
Replace the flapper
Unhook the old flapper from the overflow tube pegs. Snap the new flapper in place and reconnect the chain — leave about half an inch of slack.
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4
Adjust the fill valve
If water is running over the overflow tube, the water level is too high. Adjust the float arm or float ball downward until the water sits 1 inch below the top of the overflow tube.
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5
Turn water back on and test
Slowly open the shutoff valve. Let the tank fill and listen for any continued running after the fill cycle completes.
In Boston, tap water is soft (30–70 ppm). Boston's water is soft, sourced from protected upland reservoirs. Mineral buildup is minimal. Soft water can cause pin-holing in copper piping, particularly in older systems. Corrosion is a concern in pre-1950s buildings.
Plumbers in Boston typically charge $145–240/hr. Most homeowners budget $800–2,500 for common repairs like fixture replacement, drain clearing, or valve repairs.
Massachusetts requires state licensing for plumbers. Boston has strict codes and inspections. Homeowner exemptions limited to minor repairs.
Pre-1950s homes dominant in urban core. Galvanized piping with severe corrosion is common. Cast-iron drain stacks are standard. Copper replacement is frequent in renovations. Soft water can cause pin-holing. Freeze-thaw cycles cause burst risk. Many homes have radiant heat systems.
DIY in Boston: Boston's strict code requirements, historic preservation rules, and high licensing standards make DIY repairs very restricted. Most homeowners must hire licensed professionals. Permits are expensive and inspections are thorough. The cost of non-compliance is high.
- The tank or bowl has visible cracks.
- The toilet rocks or is loose at the base — this may indicate a wax ring failure.
- Water appears on the floor around the base after flushing.
Let Uncle AI diagnose it first.
Describe the problem. Uncle AI asks the right questions and tells you exactly what's broken — and whether you should fix it yourself or call someone in Boston.
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