High Water Bill but No Visible Leak? Here's Where to Look

The bill arrives and it's double what you usually pay. You walk the house and see nothing: no puddles, no drips, no wet ceilings. It's one of the most common and frustrating calls plumbers get in Texas. The good news is that the water is going somewhere, and with a systematic approach you can usually figure out where. This guide covers the hidden places water goes, the order to check them, and when a slab leak is the likely answer.

First, make sure it's a real increase

Before hunting for a leak, rule out the paperwork.

• Compare usage, not dollars. Rates and fees change. Look at gallons or thousands of gallons used, which are printed on most bills.
• Check the billing period. A bill covering 35 days instead of 28 will be higher even with identical use.
• Look for an estimated read. If the utility estimated your last bill, this one may include a catch-up.
• Consider the season. Summer irrigation in Texas can easily double or triple usage. Compare to the same month last year if you can.
• Think about life changes. Guests, a new pool, a new lawn, or a teenager who discovered long showers all count.

If the increase survives these checks, you're likely dealing with a leak.

Prove it with the meter

Turn off every fixture, appliance and irrigation zone, then watch your meter's leak indicator for one to two hours. If it moves, water is escaping. Our step-by-step meter test guide covers this in detail, including how to use the house shut-off valve to tell a yard leak from an indoor leak.

The hidden places water goes

Here are the usual suspects, roughly from most common to least, with how to check each.

Toilets

A worn flapper or a fill valve that never quite shuts off can waste a surprising amount of water without making much noise. Put food coloring in each tank and wait 15 minutes without flushing. If color appears in the bowl, you've found a leak. Also listen for the tank refilling on its own every so often.

Irrigation systems

Sprinkler systems are the biggest water users in many Texas homes, and their leaks hide underground. Look for soggy patches, unusually green strips of grass, water bubbling around a head, or a valve box full of water. A controller programmed wrong after a power outage can also run zones far more than you intended.

Pool auto-fill

If your pool tops itself up automatically, a pool leak or a stuck fill valve can show up as a high bill. Turn off the auto-fill and mark the water level with tape. If the level drops much more than evaporation would explain, the pool may be leaking.

Water softeners and filtration

A softener stuck in regeneration sends water to the drain continuously. So can a malfunctioning reverse-osmosis system. Listen for running water near these units when nobody is using any.

Water heater

Check the temperature and pressure relief valve's discharge pipe. If it's dripping or wet, the valve may be releasing water. Look at the base of the tank for moisture as well.

Outdoor faucets and the yard line

A dripping hose bib is easy to spot. A leak in the line between the meter and the house is not. If the meter keeps moving after you close the house's main shut-off, the leak is in that yard line or an irrigation line connected before the shut-off.

Under the slab

If you've ruled out everything above and the meter still moves with the house shut-off open but stops when it's closed, the leak is inside the house and hidden. In a slab home, the supply lines under the concrete are the prime suspect.

Clues that point to the slab

These signs, alongside a high bill, make a slab leak more likely:

• A warm spot on the floor
• The sound of running water when nothing is on
• A water heater that runs constantly
• Damp carpet or cupped wood flooring near a plumbing wall
• A musty smell near the floor
• New cracks in tile or drywall

If any of these show up, it's time for professional detection rather than more guessing.

How professional detection narrows it down

A leak detection plumber starts where you left off. They confirm the leak with a meter and a pressure test, isolate the hot and cold sides, then separate individual lines until the leaking one is identified. That line's route is traced under the floor, and the exact spot is found with acoustic listening, thermal imaging or tracer gas. Two methods should agree before the spot is marked. Our Our Process page walks through all nine steps.

Don't forget the drains

A drain leak under the slab won't raise your water bill, because it leaks water you already used. But it can cause damp floors, odors and soil washout. If your bill is normal but you smell sewage or see dampness near bathrooms, ask about a hydrostatic test of the drains.

Asking for a leak adjustment

Many Texas cities and MUDs offer a partial credit for water lost to a hidden leak, such as one under the slab, once it's repaired. Most require:

• A paid invoice from a plumber showing the leak was repaired
• A request within a set number of days after the repair
• That the leak was not caused by negligence

Many limit credits to one per year. Call your utility's billing office early to learn its rules and deadline, and keep your detection report and repair invoice together. Our FAQs include more on water bill credits.

How much water a small leak wastes

It's easy to underestimate a leak you can't see. A pinhole in a pressurized line runs every minute of every day. Even a leak that only moves the meter's leak indicator slowly can add up to thousands of gallons over a billing cycle or two, which is why the bill is often the first sign. The longer it runs, the more you pay and the more soil the water can move under the slab.

Read your usage like a detective

Many Texas utilities now offer online portals that show daily or even hourly water use from smart meters. If yours does, it can save you a lot of guessing. Look at the hours between about 2 a.m. and 5 a.m., when most households use almost nothing. If usage never drops to zero during those hours, something runs constantly, and a constant flow is the signature of a leak in a pressurized line. If usage spikes at the same times every few days, look at the irrigation schedule or the water softener's regeneration cycle instead.

Compare weekdays to weekends, and the weeks you were traveling to the weeks you were home. A leak doesn't take vacations. If the house used water while it was empty, that's strong evidence.

Why the bill can jump suddenly

Homeowners often ask why a leak that must have started small suddenly doubles the bill. There are a few reasons. Pinholes in copper tend to grow as water erodes the edges of the hole. Soil movement can turn a weeping joint into a separated one. And in many Texas cities, water is billed in tiers, so the first extra thousand gallons cost less than the next. A modest leak can push you into a higher tier and make the increase look dramatic.

A simple checklist

1. Confirm the increase is real, using gallons, not dollars.
2. Do the meter test with everything off.
3. Close the house shut-off to split yard from house.
4. Check toilets, irrigation, pool, softener and water heater.
5. Look for slab leak signs: warm spots, sounds, damp floors.
6. Book professional detection if the leak is still hidden.
7. Ask your utility about a leak adjustment after the repair.

This is one of the most common calls from homeowners in Mansfield, Lewisville and Rockwall, where many homes are now 20 to 30 years old.

The bottom line

A high bill with no visible leak almost always has an explanation. Work through the checklist and you'll either find the culprit yourself or narrow it to a hidden leak. If it's under the slab, contact us and a licensed Texas plumber can find it without breaking your floor to search.