Why Is My Toilet Constantly Running?

A toilet constantly running water is typically caused by three main issues: a worn flapper seal allowing water to leak from the cistern into the bowl, a faulty fill valve that won't shut off properly, or an incorrectly adjusted float mechanism. In the UK, running toilets waste 200-400 litres daily—adding up to £300 yearly on metered bills. The good news? Most causes are fixable in under 30 minutes with basic tools, though silent leaks often go undetected for months, causing extensive damage.

Understanding Your Toilet's Inner Workings

Before we fix anything, you need to understand what's actually happening inside that cistern. When you flush, the flapper (or flush valve seal in modern UK toilets) lifts, releasing water from the tank into the bowl. The float then drops, triggering the fill valve to refill the cistern. Simple enough—until one component fails and water keeps running continuously.

The BBC reported that 400 million litres of water leak from UK toilets every day. That's not a typo. Thames Water estimates that 1 in 20 households has a leaky loo, and most homeowners don't even realise it's happening.

What Causes a Toilet to Keep Running Water?

After inspecting thousands of running toilets across the Southwest, I can tell you the causes fall into clear patterns. Here's what's actually going wrong when your toilet constantly runs:

Different Types of Running Toilets (And What They Mean)

Not all running toilets are created equal. Understanding the pattern helps identify the cause faster:

Continuous Running

Water constantly flows without stopping. This typically indicates a flapper seal that won't close properly or a fill valve that won't shut off. You'll hear continuous water flow, though sometimes it's so quiet you only notice when the house is silent at night.

Intermittent or Phantom Flush

Your toilet randomly runs for a few seconds every 10-15 minutes, like someone's just flushed it. This "phantom flush" or "ghost flushing" indicates a slow leak from the cistern into the bowl. The water level drops gradually until the fill valve kicks in to refill it.

This is particularly insidious because many people assume it's normal. It's not. Even a toilet running every 5 minutes is wasting significant water and indicates a failing seal.

Running After Flush Only

The toilet continually runs for several minutes after flushing, then stops. This usually means the fill valve is working but taking too long to shut off, or the float needs adjustment. Sometimes it's debris stuck in the fill valve mechanism.

UK Toilet Types and Their Specific Issues

Understanding UK Toilet Systems

UK toilets have evolved significantly over the past 20 years. Understanding your specific system is crucial for proper diagnosis and repair.

Dual Flush Toilets (Push Button)

These became standard in UK homes from the early 2000s onwards. Instead of traditional siphon systems, they use drop valve flush mechanisms with two buttons—typically a full flush (6 litres) and half flush (3 litres).

Common problems with dual flush systems:

• Flush valve seal deterioration causing constant trickling
• Button mechanism sticking in the pressed position
• Air pressure issues in pneumatic button systems
• Calcium buildup preventing proper seal closure (particularly common in Devon and Cornwall's hard water areas)
• Incorrect water level causing continuous overflow

If your dual flush toilet is constantly filling or won't stop running after pushing the button, the flush valve seal is almost certainly worn. These seals cost £5-15 from plumbers' merchants and most keen DIYers can replace them in under 20 minutes. For complex issues with water leaks in your home, sometimes professional diagnosis saves both time and money.

Siphon vs Drop Valve Systems

Older UK toilets (pre-2000s) typically used siphon flush systems—robust, reliable, but water-inefficient. When these run continuously, it's usually because the siphon diaphragm has perished. Replacement requires removing the entire cistern from the pan—not a quick job.

Modern drop valve systems are easier to maintain but more prone to seal failure. The good news? Repairs are simpler and parts more readily available.

Concealed Cisterns (Wall-Mounted)

Contemporary bathrooms often feature concealed cisterns hidden behind wall panels or furniture units. When these run continuously, diagnosis becomes trickier because you can't easily see what's happening.

Access typically requires:

• Removing the flush plate (usually secured with clips)
• Unfastening the flush rods from the central frame
• Removing plastic access panels if fitted
• Sometimes removing entire furniture units

The internal mechanisms are identical to standard close-coupled toilets, but repairs take longer due to access issues. If you're not confident, call a professional—I've seen too many damaged wall panels from DIY attempts gone wrong.

Close-Coupled Toilets

The most common UK toilet type—cistern sits directly on the back of the pan with a large gasket between them. These are the easiest to diagnose and repair because you simply lift off the lid to access everything.

When water constantly runs in these toilets, check the flapper seal first, then the fill valve, then the float adjustment. That order solves 95% of issues.

The Real Cost of Ignoring a Running Toilet

Let me be blunt about what this actually costs, because most articles gloss over the financial damage:

These figures are based on current UK water rates averaging £2 per cubic metre (combined water and sewerage). If you're not on a water meter, you won't see direct cost increases, but you're still wasting this much water—and contributing to the UK's water stress problems.

The Environmental Impact You're Not Considering

Beyond your wallet, there's the environmental angle that most people ignore. The South East of England is classified as "seriously water-stressed" by the Environment Agency. Cornwall and Devon, while wetter, still face summer shortages and hosepipe bans.

According to the Environment Agency, England could face significant water deficits by 2050 unless we reduce per capita consumption from 140 litres to 100 litres daily. A single running toilet can waste double the average person's daily consumption.

Think about it this way: every litre your toilet wastes is a litre that needs processing at treatment plants (energy-intensive) and pumping to your home (more energy). It's not just about water—it's about the carbon footprint of treating and moving that water.

How to Detect Silent Toilet Leaks (The Tissue Test)

Many running toilets are virtually silent. You won't hear any water flow, see any ripples in the bowl, or notice anything obviously wrong. Yet they're still wasting hundreds of litres daily.

This simple test reveals silent leaks that water company engineers use to identify problems. If you've received a South West Water leak notification, this is likely how they identified the issue from your meter readings alone.

Alternative method: Add food colouring to your cistern. Wait 30 minutes without flushing. If colour appears in the bowl, you've got a leak even if you can't hear or see it.

DIY Fixes for Toilet Constantly Running

Right, let's get practical. Here's how to fix the most common causes yourself:

Fix #1: Adjust the Float (5 Minutes)

This solves about 20% of running toilet issues and costs absolutely nothing.

Fix #2: Replace the Flapper Seal (20 Minutes)

For dual flush toilets, you're replacing the flush valve seal rather than a flapper. The principle is identical, though you might need to twist the entire valve unit anticlockwise to remove it. If you're unsure how to find water leaks beyond the obvious toilet issues, sometimes the problem runs deeper.

Fix #3: Clean or Replace the Fill Valve (30 Minutes)

Fix #4: Shorten or Replace Flush Chain (5 Minutes)

If your chain is too long and getting caught under the flapper:

• Disconnect chain from flush lever
• Shorten by hooking it higher up on the lever arm
• Leave just 12-25mm of slack when flapper is closed
• Trim excess chain with wire cutters to prevent future tangling
• Test flush to ensure flapper opens fully and closes properly

Specific Fixes for Dual Flush Push Button Toilets

Push button toilets require slightly different approaches:

Accessing the Cistern

1. Press down on the outer edges of the button assembly
2. Turn anticlockwise until it unscrews (usually 1-2 full turns)
3. Lift out the button unit carefully
4. Remove cistern lid

Some models have a small screw beneath the buttons—gently prise out the buttons with a screwdriver, then undo the screw.

Replacing Dual Flush Valve Seal

1. Turn off water and flush to empty cistern
2. Twist the central flush valve clockwise to remove (it lifts out)
3. Check the holder beneath for limescale buildup—clean thoroughly
4. Inspect the rubber washer on the valve bottom
5. If worn, cracked, or hardened, replace it (bring old one to match)
6. Clean any debris from the seating area
7. Reinstall valve by twisting anticlockwise to lock
8. Replace button assembly
9. Turn water on and test both flush buttons

When to Call a Professional (Don't Waste Time on These)

After three decades in the trade, I can tell you when DIY stops being cost-effective:

Here's something most articles won't tell you: if you've spent more than an hour faffing about with a toilet and it still runs, call someone. Your time has value, and sometimes the issue needs professional diagnosis because there's an underlying problem you can't see.

For instance, I recently investigated a toilet that kept running despite three flapper replacements. Turned out the flush valve seat was severely corroded—something the homeowner couldn't spot because it was beneath the flapper. Entire valve needed replacing, which meant temporarily removing the toilet from the floor. That's not a DIY job for most people.

Preventing Future Running Toilet Problems

Right, you've fixed it. Now keep it fixed:

What NOT to Do

• Don't use in-cistern cleaning tablets—they corrode rubber seals faster than anything else
• Don't ignore intermittent running—phantom flushes indicate slow leaks that worsen
• Don't overtighten connections—you'll crack ceramic or strip plastic threads
• Don't use WD-40 on fill valves—petroleum-based lubricants damage rubber components
• Don't leave the lid off long-term—dust and debris get into mechanisms
• Don't assume it's "just how toilets work"—properly maintained toilets don't run constantly

Understanding Water Meter Impact and Company Notifications

If you're on a water meter, running toilets show up quickly on consumption reports. South West Water (which serves most of Cornwall and Devon) now sends leak notifications when they detect unusual consumption patterns.

How Water Companies Detect Your Toilet Leak

Modern smart meters track water usage patterns. When they detect continuous flow (even small amounts) over extended periods, it flags as a potential leak. The water company's algorithm can distinguish between normal daily use and constant background flow from a running toilet.

You'll typically receive a letter or text alert saying something like: "Our records indicate you may have a leak at your property." Don't ignore these. Their data is usually accurate, and catching leaks early prevents massive bills.

What Happens if You Ignore It

Water companies generally give you reasonable time to fix leaks. However, if you ignore notifications and consumption remains high for months, you'll pay for every litre wasted. Unlike some utilities, water companies won't retrospectively reduce bills for leaks you should've noticed but didn't fix.

Some companies offer a one-time leak allowance if you can prove you fixed it promptly upon discovery. Keep receipts for any parts you purchase and photograph the repair for documentation.

Other Reasons Your Toilet Might Be Running

Occasionally, the cause isn't your toilet mechanism at all:

High Water Pressure

Excessively high mains pressure (above 5 bar) can cause fill valves to leak and seals to fail prematurely. If your toilet continually refills and you live in a low-lying area with known high pressure, install a pressure-reducing valve on your main supply. This protects not just your toilet but all your plumbing fixtures.

Frozen or Blocked Overflow Pipe

External overflow pipes can freeze in winter or become blocked by debris. When this happens, water backs up and appears to make your toilet run continuously. Check the external discharge point—it should be clear and show no signs of blockage. For comprehensive information about what to do if you think you have a water leak, understanding all potential causes helps.

Shared Plumbing Issues (Flats and Apartments)

In multi-occupancy buildings, sometimes your toilet runs because of issues in the building's plumbing system rather than your specific toilet. Pressure fluctuations from other units can affect your fill valve operation. If you've done everything right and the problem persists, speak with building management about system-wide pressure checks.

When You Need Professional Leak Detection

Sometimes what seems like a simple running toilet actually indicates a bigger problem lurking beneath:

I've investigated dozens of cases where homeowners spent weeks trying to fix a toilet, only to discover the real leak was in the supply pipe beneath the bathroom floor or in the waste pipe behind the wall. Thermal imaging cameras can spot these issues in minutes.

Signs you need professional leak detection rather than just toilet repair:

• Water meter spinning even with everything turned off including the toilet
• Damp patches on walls or ceiling near the toilet
• Musty smell in the bathroom that persists after fixing the toilet
• Floor feels soft or spongy around the toilet base
• Multiple fixtures in the bathroom having issues simultaneously
• Your toilet and your central heating system both losing pressure

Will Home Insurance Cover Running Toilet Damage?

Here's the insurance reality most people don't understand:

What's typically covered:

• Sudden and unexpected escape of water (burst pipe, sudden seal failure)
• Damage to property caused by the leak (ceiling damage below bathroom)
• Trace and access costs to find hidden leaks

What's NOT covered:

• Gradual deterioration and wear (slow-developing flapper wear)
• Lack of maintenance (ignoring obvious running water for months)
• The faulty component itself (you pay for the new flapper)
• Water bills from wasted water

If your running toilet causes damage to rooms below (common in flats), insurers will investigate how long the problem existed. If they determine you should've noticed and fixed it earlier, they may deny the claim. This is why regular checks matter—both for your wallet and insurance coverage.

Common Questions About Running Toilets (The Answers That Actually Help)

Can I use WD-40 on a toilet fill valve?

No. Absolutely not. WD-40 is petroleum-based and will deteriorate rubber seals and plastic components. If your fill valve is sticking, clean it with water or replace it. Using WD-40 might temporarily solve the problem but causes bigger failures within weeks.

Is it worth trying to fix a running toilet or should I replace the whole thing?

Unless your toilet is cracked or severely corroded, it's almost always worth fixing. A complete internal replacement kit costs £30-50 and gives you essentially a new toilet mechanically. Replacing the entire toilet costs £100-300 plus installation. Fix it first unless there are other reasons to upgrade.

How do I know if my toilet flapper needs replacing?

Remove it and check for:

• Cracks or tears in the rubber
• Hardening or loss of flexibility (it should bend easily)
• Black residue when you touch it (indicates deterioration)
• Warping or deformation that prevents flat sealing
• Age over 5 years (replace as preventive maintenance)

Should I call a plumber for a running toilet?

Try the simple fixes first (adjust float, clean fill valve). If those don't work within an hour or you're uncomfortable working with plumbing, yes, call a professional. Plumbers typically charge £40-80 for this repair plus parts. That's money well spent compared to months of wasted water or botched DIY that makes things worse. When wondering who to call for leak under floor or ceiling issues related to your toilet, the same principle applies.

How to adjust ballcock in toilet cistern in the UK?

For older brass ballcock systems:

1. Gently bend the brass rod downward to lower the float
2. Bend upward to raise the float
3. Make small adjustments—brass can fatigue and break
4. Target water level: 25mm below overflow pipe

For modern fill valves:

1. Look for an adjustment screw on top of the valve
2. Turn clockwise to lower water level
3. Turn anticlockwise to raise water level
4. Some have a clip that slides up/down the rod instead

What happens if a toilet runs all night?

Assuming a moderate leak (200 litres/day), one night wastes approximately 67 litres. On a meter, that's about 13-17p per night. Doesn't sound like much, but over a year that's £47-62 for absolutely nothing. More importantly, continuous running accelerates wear on all toilet components, leading to bigger failures. And you're contributing to unnecessary water treatment and environmental impact.

Is it bad to leave a toilet that is constantly running?

Yes, for multiple reasons:

• Financial cost accumulates daily
• Environmental waste in water-stressed areas
• Increased wear on toilet components
• Potential insurance complications if damage occurs
• Possible violation of water use regulations in drought areas
• Your contribution to the 400 million litres wasted daily from UK toilets

How much water can a running toilet use in 30 days?

Depends on severity:

• Minor leak: 1,500-3,000 litres/month
• Moderate leak: 6,000-12,000 litres/month
• Severe leak: 30,000-60,000 litres/month
• Critical leak: 120,000-240,000 litres/month

For perspective, the average UK household uses about 142,000 litres annually. A severe running toilet can waste that much in just 2-5 months.

Can a constantly running toilet increase the water bill?

If you're on a water meter, absolutely. Even a minor leak adds £50-100 annually. Moderate leaks add £200-400. Severe cases can double or triple your water bill. If you're on a fixed rate (unmetered), you won't see direct cost increases, but you're still using the water and contributing to overall water stress in your area.

Is my toilet running costing me money?

Only if you're on a water meter. Check your billing type:

• Metered: Yes, every litre costs money
• Unmetered (rateable value): No direct bill increase, but you're wasting water and energy

Even on unmetered billing, consider switching to a meter if you have a leak—the savings from fixing it might make metering worthwhile. Most water companies offer free meter installation and a trial period.

Final Thoughts: Don't Flush Money Down the Loo

After 30 years investigating water issues across Cornwall and Devon, I can tell you this: most running toilets are simple fixes that homeowners overcomplicate. The flapper seal or flush valve costs less than a takeaway curry, takes 20 minutes to replace, and saves hundreds annually.

But here's what matters more than the money—we're in a genuinely water-stressed country. The Environment Agency isn't exaggerating when they warn about 2050 deficits. Every litre your toilet wastes is a litre that needs treating, pumping, heating (for hot water systems), and disposing of. It's not just your bill—it's everyone's future water security.

The tissue test takes 5 minutes to set up and could reveal a silent leak wasting 200 litres daily. Do it tonight. If you find a leak, fix it this weekend. If the fix doesn't work, call someone who knows what they're doing rather than guessing for weeks. Sometimes issues like mysterious wet floors in your house connect to toilet problems you hadn't considered.

Your toilet shouldn't run constantly, intermittently, or randomly. If it does, something's broken. Fix it, save money, save water, and stop contributing to the 400 million litres wasted daily from UK toilets. That's not just good sense—it's basic responsibility.