Why Does My Toilet Keep Running? 7 Fixes That Work

Why Your Toilet Keeps Running (And How to Fix It): Expert Solutions from San Jose’s Trusted Plumbers

That constant sound of running water from your bathroom isn’t just annoying—it’s literally money going down the drain. A toilet that won’t stop running can waste up to 200 gallons of water daily, costing you over $500 per year in wasted water. Whether it’s a phantom flush that happens randomly or a toilet that runs continuously after every flush, the expert plumbers at Drain and Water are here to help you diagnose and fix the problem.

As a local, family-owned plumbing company serving Santa Clara County and San Mateo County since our founding, we’ve repaired thousands of running toilets across San Jose, Palo Alto, Sunnyvale, Redwood City, and throughout the Bay Area. With our 5-star Google rating and commitment to customer satisfaction, we’ve become the go-to plumbing experts for homeowners from historic properties built in the 1800s to contemporary developments. In this comprehensive guide, we’ll walk you through the 7 most common causes of running toilets and show you exactly how to fix them—saving you time, money, and frustration.

Understanding Why Your Toilet Keeps Running

Before we dive into solutions, it’s important to understand what’s happening. Your toilet tank contains several interconnected components that work together to flush and refill your toilet. When one part fails or becomes misaligned, water continuously leaks from the tank into the bowl, triggering the fill valve to keep refilling the tank. This creates that telltale running sound.

According to the EPA, toilets account for nearly 30% of an average home’s indoor water use. When yours is running constantly, that percentage skyrockets—along with your water bill. At Drain and Water, we’ve seen firsthand how a simple running toilet can add hundreds of dollars to annual utility costs for Bay Area homeowners.

Pro Tip #1: Before you start troubleshooting, confirm your toilet is actually running continuously. Sometimes a toilet that was just flushed can take 10-15 minutes to fully refill, especially if you have low water pressure—a common issue in older neighborhoods throughout San Jose and surrounding communities. If the sound stops after 15 minutes, you may have a different issue, such as a slow-filling toilet or sediment buildup in your supply line.

The 7 Most Common Reasons Your Toilet Keeps Running (And How to Fix Them)

1. Worn or Damaged Flapper

The Problem: The flapper is a rubber seal at the bottom of your tank that lifts when you flush and closes to allow the tank to refill. Over time, flappers become warped, brittle, or coated with mineral deposits—especially in Bay Area homes with hard water. When the flapper doesn’t seal properly, water continuously trickles into the bowl.

How to Diagnose:

Perform the food coloring test:

• Add 4-6 drops of food coloring to your tank (don’t flush)
• Wait 30 minutes
• If color appears in the bowl, your flapper is leaking

The Fix:

1. Turn off the water supply valve (located behind or beside the toilet)
2. Flush to drain the tank
3. Unhook the old flapper from the overflow tube pegs
4. Take it to your local hardware store to find an exact match
5. Install the new flapper and reconnect the chain
6. Turn water back on and test

Cost: $5-$15 for a replacement flapper

Pro Tip #2: Avoid using in-tank bleach tablets or drop-in cleaners. These products contain harsh chemicals that deteriorate rubber components like flappers and gaskets, significantly shortening their lifespan. Instead, use a toilet bowl cleaner applied directly to the bowl, or schedule regular professional cleaning to maintain your toilet without damaging internal parts.

Need help with your water quality? Hard water is particularly common throughout Santa Clara and San Mateo Counties, and it can destroy toilet components faster. Contact Drain and Water at (408) 564-0580 for expert water leak detection services and professional plumbing solutions that address the root cause of your plumbing issues.

2. Incorrect Water Level or Float Position

The Problem: Your toilet’s float (either a ball float or cup float) tells the fill valve when to stop filling the tank. If it’s set too high, water spills into the overflow tube, draining into the bowl and triggering constant refills. If it’s too low, your toilet won’t flush properly.

How to Diagnose:

• Remove the tank lid
• Check if water is flowing into the overflow tube (the vertical pipe in the center)
• The water level should sit about 1 inch below the top of the overflow tube

The Fix:

For Float Cup Valves (modern toilets):

• Locate the adjustment screw or clip on the fill valve
• Turn the screw clockwise to lower the water level
• Or slide the float cup down the valve shaft
• Flush and check the water level

For Ball Float Valves (older toilets):

• Gently bend the float arm downward to lower the water level
• Be careful not to crack the arm
• Flush and adjust as needed

Pro Tip #3: Mark your ideal water level with a permanent marker inside the tank. This gives you a visual reference point for future adjustments and makes it easier to spot when something’s wrong. Place the mark about 1 inch below the overflow tube opening.

3. Faulty or Clogged Fill Valve

The Problem: The fill valve (also called a ballcock) controls water flow into the tank. Mineral deposits, sediment, and debris can clog the valve, preventing it from shutting off completely. This causes a constant hissing sound and water that never stops running.

How to Diagnose:

• Listen for a constant hissing sound
• Check if water level slowly rises above the fill line
• Look for short bursts of refilling when no one has flushed

The Fix:

To Clean:

1. Turn off the water supply
2. Remove the fill valve cap (usually a quarter-turn)
3. Hold a cup over the valve
4. Turn water on for 10 seconds to flush out debris
5. Replace the cap and test

To Replace:

1. Turn off water and flush to empty tank
2. Disconnect the supply line
3. Unscrew the locknut under the tank
4. Remove the old fill valve
5. Install the new valve according to package instructions
6. Reconnect supply line and turn water on

Cost: $10-$25 for a new fill valve

Pro Tip #4: When replacing a fill valve, consider upgrading to a WaterSense-certified model. These valves are designed to be more efficient and durable, and they often include built-in features that prevent overfilling and reduce water waste. The small upfront investment pays for itself through lower water bills—especially important given Bay Area water rates.

Experiencing frequent plumbing issues? Sediment buildup often indicates larger problems with your water supply or pipes. Drain and Water’s expert plumbers can schedule a comprehensive plumbing inspection to identify hidden issues before they become expensive emergencies. With 24/7 emergency service available throughout San Jose, Campbell, Cupertino, Palo Alto, and all of Santa Clara and San Mateo Counties, we’re here when you need us most. Call (408) 564-0580 today.

4. Stuck or Misaligned Flush Handle and Chain

The Problem: The chain connects your flush handle to the flapper. If it’s too tight, the flapper won’t seal after flushing. If it’s too loose, the handle won’t lift the flapper enough to flush properly. A stuck handle can also keep the flapper open, causing continuous running.

How to Diagnose:

• Flush and watch the chain’s movement
• Check if the handle returns to its resting position
• Look for chain tangled under the flapper
• Test if the handle feels loose or stuck

The Fix:

For Chain Issues:

• Adjust the chain to have about ½ inch of slack
• Remove any excess links
• Ensure the chain isn’t tangled or caught under the flapper

For Handle Issues:

• Tighten the mounting nut inside the tank (turn counterclockwise—it’s reverse-threaded)
• Don’t overtighten or you’ll crack the porcelain
• If the handle is broken, replace it by disconnecting the chain, unscrewing the nut, and installing a new handle

Cost: $5-$15 for a new handle

5. Cracked or Improperly Sized Overflow Tube

The Problem: The overflow tube prevents your tank from overflowing by directing excess water into the bowl. If it’s cracked, too short, or if the refill tube isn’t properly positioned, water continuously drains into the bowl.

How to Diagnose:

• Inspect the overflow tube for visible cracks
• Check that the refill tube is clipped to the overflow tube
• Ensure the refill tube isn’t inserted too far down (which can create a siphon effect)

The Fix:

• If cracked, the overflow tube needs replacement (this is more complex and may require professional help)
• Reposition the refill tube so it clips to the outside of the overflow tube
• The refill tube should direct water into the overflow tube without being submerged

Pro Tip #5: The refill tube should only extend about 1 inch into the overflow tube. If it goes deeper, it can create a siphon that continuously pulls water from the tank into the bowl. This is a commonly overlooked cause of phantom flushing that many DIYers miss—but our experienced technicians at Drain and Water spot it immediately.

6. High Water Pressure

The Problem: Excessive water pressure (above 80 psi) can overwhelm your toilet’s fill valve, preventing it from closing completely. This is especially common in older Bay Area homes and neighborhoods with municipal water systems that haven’t been pressure-regulated.

How to Diagnose:

• Purchase an inexpensive pressure gauge from a hardware store
• Attach it to an outdoor hose bib
• Ideal pressure is 40-60 psi
• Anything above 80 psi is problematic

The Fix:

• Install a pressure-reducing valve (PRV) on your main water line
• This is a job for a licensed plumber
• A PRV protects all your plumbing fixtures, not just your toilet

Cost: $300-$600 for professional PRV installation

Pro Tip #6: High water pressure doesn’t just affect your toilet—it puts stress on all your plumbing fixtures, appliances, and pipes. Signs of high water pressure include banging pipes (water hammer), leaking faucets, and appliances that fail prematurely. If you suspect high pressure, address it immediately to prevent costly damage throughout your home.

Concerned about your home’s water pressure? The licensed, professional plumbers at Drain and Water can provide a complete water pressure assessment and expert pressure-reducing valve installation. Serving properties from historic Victorian homes in San Jose to modern developments in Mountain View, we have the expertise to protect your entire plumbing system and extend the life of your fixtures. Contact us at (408) 564-0580 or visit drainandwater.com for same-day service.

7. Blockage in the Toilet or Drain Line

The Problem: A partial blockage in your toilet trap or drain line can cause your toilet to run continuously as it tries to maintain proper water levels. The toilet keeps attempting to flush away the obstruction, resulting in constant running.

How to Diagnose:

• Slow draining after flushing
• Gurgling sounds
• Water level fluctuations in the bowl
• Toilet runs after every flush

The Fix:

• Try plunging with a toilet plunger (not a sink plunger)
• Use a toilet auger to break up deeper clogs
• For persistent blockages, professional drain cleaning is necessary

Pro Tip #7: Never ignore a slow-draining toilet. What starts as a minor inconvenience can quickly escalate into a complete blockage, sewage backup, or even pipe damage. If plunging doesn’t resolve the issue within 2-3 attempts, it’s time to call a professional before the problem worsens.

Dealing with frequent clogs or slow drains? This could indicate a more serious issue with your sewer line—potentially tree root intrusion, pipe corrosion, or structural damage. Drain and Water specializes in advanced drain and sewer diagnostics, including professional camera inspection services that identify blockages, tree root intrusion, or pipe damage before it causes a backup. Our expert technicians use state-of-the-art video inspection technology to pinpoint problems with precision. Schedule your inspection today by calling (408) 564-0580.

Step-by-Step Diagnostic Process

If you’re not sure which issue is causing your toilet to run, follow this systematic approach recommended by Drain and Water’s expert plumbers:

Step 1: Perform the Dye Test
Add food coloring to the tank and wait 30 minutes. Color in the bowl = flapper leak.

Step 2: Check Water Level
Remove the lid and see if water is flowing into the overflow tube. If yes, adjust the float.

Step 3: Listen for Sounds

• Hissing = fill valve issue
• Trickling = flapper or valve seat problem
• Gurgling = possible blockage

Step 4: Inspect Components
Look for visible damage to the flapper, chain, overflow tube, and fill valve.

Step 5: Test Water Pressure
Use a pressure gauge to rule out high-pressure issues.

Step 6: Check for Blockages
Flush and watch how water drains. Slow drainage indicates a clog.

When to Call Drain and Water’s Professional Plumbers

While many running toilet issues can be fixed with DIY solutions, some situations require the expertise of licensed professionals. Here’s when to call Drain and Water:

✓ You’ve tried multiple fixes without success – The problem may be more complex than it appears, and our experienced technicians can quickly diagnose the root cause

✓ Water is leaking at the base of the toilet – This indicates a wax ring failure or cracked toilet that requires immediate professional attention

✓ Your toilet is more than 15 years old – Older toilets waste significantly more water; replacement may be more cost-effective, and we can help you choose the right high-efficiency model

✓ You notice cracks in the tank or bowl – This requires immediate replacement to prevent water damage

✓ You’re uncomfortable working with plumbing – There’s no shame in calling a pro; DIY mistakes can lead to expensive water damage

✓ You need same-day or emergency service – We offer 24/7 emergency plumbing services throughout our service area

As a local, family-owned plumbing company with a 4.9-star Google rating, Drain and Water has seen it all. Our team of licensed, professional plumbers can quickly diagnose the issue, provide upfront pricing with no hidden fees, and fix your running toilet the same day. We proudly serve homeowners and businesses throughout Santa Clara County (San Jose, Santa Clara, Campbell, Cupertino, Saratoga, Los Gatos, Palo Alto, Sunnyvale, Milpitas, Mountain View, Morgan Hill, Gilroy, Los Altos) and San Mateo County (Menlo Park, Atherton, Redwood City, San Mateo, Burlingame, San Carlos, Foster City, and more).

Ready to fix your running toilet? Call (408) 564-0580) or visit drainandwater.com to schedule your service today.

Preventive Maintenance: Stop Problems Before They Start

An ounce of prevention is worth a pound of cure—especially when it comes to plumbing. Follow these maintenance tips from Drain and Water’s expert plumbers to keep your toilet running smoothly:

Annual Inspection Checklist:

✓ Inspect the flapper for wear, warping, or mineral buildup
✓ Check the chain for proper length and condition
✓ Test the fill valve for smooth operation
✓ Verify water level is correct
✓ Look for leaks at the base and supply line connections
✓ Clean mineral deposits from the valve seat

Best Practices:

• Replace flappers every 3-5 years (more frequently in Bay Area hard water areas)
• Use WaterSense-certified replacement parts
• Avoid chemical drop-in cleaners
• Address small issues immediately before they worsen
• Consider upgrading to a high-efficiency toilet if yours is over 15 years old

Pro Tip #8: Create a simple maintenance schedule by setting an annual reminder on your phone. Spending 15 minutes once a year inspecting your toilet’s internal components can prevent emergency repairs and save hundreds of dollars in wasted water. The best time to do this is when you change your HVAC filters or test your smoke detectors—bundle your home maintenance tasks together.

Want worry-free plumbing? Ask Drain and Water about our preventive maintenance services that include comprehensive plumbing inspections, priority scheduling, and exclusive discounts on repairs. We’ll catch small issues before they become big problems—saving you money and stress. Contact us at (408) 564-0580 to learn more.

The Cost of Ignoring a Running Toilet

Still thinking about putting off that repair? Consider these numbers:

• A running toilet wastes 200+ gallons per day
• That’s 73,000 gallons per year
• At Bay Area water rates, that’s $500-$700 annually in wasted water
• Over 5 years, you’ll waste $2,500-$3,500

Compare that to:

• DIY flapper replacement: $5-$15
• Professional toilet repair from Drain and Water: $150-$300
• New high-efficiency toilet installation: $300-$600

The math is clear: fixing a running toilet is one of the best investments you can make in your home—and Drain and Water makes it easy with upfront pricing, same-day service, and customer satisfaction guaranteed.

Upgrade to a High-Efficiency Toilet with Drain and Water

If your toilet is more than 15 years old, replacement might be more cost-effective than repeated repairs. Older toilets use 3.5-7 gallons per flush, while modern WaterSense-certified toilets use just 1.28 gallons per flush—without sacrificing performance.

Benefits of upgrading:

✓ Save up to 13,000 gallons of water per year
✓ Reduce your water bill by $100+ annually
✓ Fewer repairs and maintenance issues
✓ Better flushing performance
✓ Increased home value
✓ Potential rebates from your local water utility

Ready to upgrade? Contact Drain and Water for a free consultation on high-efficiency toilet installation. Our licensed plumbers will help you choose the right model for your needs and budget, and we’ll ensure proper installation for years of trouble-free operation. With financing available through Wisetack and our industry-leading warranties, upgrading your toilet has never been more affordable.

Why Choose Drain and Water for Your Plumbing Needs?

When you choose Drain and Water, you’re choosing:

✅ Local & Family-Owned – We’re your neighbors, serving the Bay Area community with pride
✅ 4.9-Star Google Rating – Trusted by thousands of satisfied customers
✅ 24/7 Emergency Service – We’re here when you need us most
✅ Licensed & Professional – Fully licensed plumbers with extensive training
✅ Upfront Pricing – No hidden fees or surprise charges
✅ Customer Satisfaction Guaranteed – We stand behind our work
✅ Same-Day Service Available – Fast response times throughout our service area
✅ Financing Available – Flexible payment options through Wisetack

Don’t let a running toilet drain your wallet. Contact the plumbing experts at Drain and Water today.

📞 Call: (408) 564-0580
🌐 Send Us a Request
📍 Location: 1913 Stone Ave, San Jose, CA 95125

Serving Santa Clara County and San Mateo County with professional plumbing services you can trust.