Nothing breaks a bathroom routine like a toilet that won’t stop running. A running toilet is usually caused by a few common issues, and most repairs fall into a few predictable cost ranges. Understanding the problem can help you decide whether to DIY or hire a plumber.

What typically causes a running toilet

A running toilet most often results from one of these problems: a faulty flapper, a misadjusted fill tube, a stuck float, a worn fill valve, or a problematic flush valve. In older toilets, the fill valve or flush valve may simply wear out and require replacement. A stuck flapper can continuously allow water to leak from the tank into the bowl.

Cost breakdown by fix type

Costs vary by part and whether you do it yourself or hire a professional. Here are typical ranges you might see:

• DIY minor adjustments (flapper, adjusting float): $10–$60
• Flapper replacement: $10–$25 for parts, plus any minimal tool costs
• Replace fill valve: $60–$150 for parts, plus labor if hired
• Replace flush valve: $100–$300 for parts and labor
• Full toilet replacement (rare in minor cases): $300–$600

Tips to save money

• DIY simple fixes like adjusting the float or replacing a flapper can save 50–70% vs. hiring a pro.
• Bring a shopping list of parts to a hardware store to compare brands and prices.
• Turn off the water and empty the tank before starting any repair to avoid leaks.

If you’re unsure about the cause or if the tank continues to run after a basic fix, it’s wise to consult a licensed plumber. A quick diagnostic can prevent wasted water and help you choose the right repair path.