High Water Bill? How to Find a Hidden Leak

A high water bill with a hidden leak behind it is one of the most common reasons homeowners call us. The good news: the first three checks below take about 30 minutes, cost nothing, and will tell you whether you actually have a leak — before you spend a dollar on help.

The Short Answer

Start with the bill itself (gallons, billing days, rate changes), then do a water meter leak test, then check toilets and irrigation. Most “mystery” high bills resolve into one of three buckets: a running toilet, an irrigation problem, or a genuine hidden leak in a pipe. Work the steps in order and you’ll know which bucket you’re in.

First, Rule Out the Innocent Explanations

Before hunting for a leak, make sure the bill itself isn’t the story:

• Compare gallons, not dollars. Rates and tiers change; usage in gallons is the honest number. Find it on each bill and compare the last 3–4 cycles.
• Check the billing period. A 35-day cycle vs. a 28-day cycle looks like a spike all by itself.
• Look for estimated reads. If the utility estimated your meter for a month or two and then took an actual read, the “spike” may be catch-up billing.
• Rate or tier changes. Crossing into a higher usage tier — common in summer — raises the per-gallon price on your top gallons.
• Household changes. Guests, a new irrigation schedule, a topped-off pool, or a kid home for summer all move the needle legitimately.

If gallons are genuinely up and nothing above explains it, keep going — you likely have a leak.

How to Do a Water Meter Leak Test

This is the single most useful DIY leak check in existence, and it takes 30 minutes:

1. Shut off everything that uses water — faucets, dishwasher, washing machine, ice maker, and especially the irrigation system (a frequent gotcha).
2. Find your water meter (usually near the street in a ground box) and note the reading, or watch the small leak-indicator dial — often a triangle or snowflake that spins with even tiny flows.
3. Wait 30 minutes without using any water. Don’t flush, don’t run anything.
4. Check again. If the reading changed or the indicator moved, water is flowing somewhere — you have a leak.

A very slow leak might not move the dial in 30 minutes; if you suspect one, repeat with a 2-hour window. Either way, a moving meter with everything off is definitive: the water is going somewhere it shouldn’t.

Is the Leak Inside or Outside? The Isolation Test

Next, find out where. Close the main shutoff valve where water enters your house, then watch the meter again:

• Meter still moves → the leak is in the underground service line between the meter and your house. This is homeowner responsibility (the utility owns up to the meter), and it’s exactly the kind of leak that needs professional locating — digging blindly along the line is expensive guesswork.
• Meter stops → the leak is inside the house: plumbing, toilets, water heater, or slab lines.

This one test saves enormous time and tells any professional exactly where to start.

Check Your Toilets — the #1 Silent Culprit

A worn flapper can waste hundreds of gallons a day with zero visible signs. The toilet dye test takes 15 minutes:

1. Put a few drops of food coloring (or a dye tablet) in the tank, not the bowl.
2. Don’t flush for 15–20 minutes.
3. If color appears in the bowl, the flapper is leaking and the toilet is running water straight through, 24/7.

Check every toilet in the house — it’s common for two to fail around the same time in older homes. A flapper is a few dollars and a 10-minute fix, and it’s the happiest possible ending to a high-bill mystery.

Don’t Forget Irrigation and the Pool

In West Palm Beach, irrigation is a top-three cause of high bills. A stuck valve, a broken head gushing underground, or a timer running extra cycles after a power outage can add thousands of gallons without a single puddle you’d notice — sandy soil drinks it fast. Walk the zones while they run and look for misting heads, sunken areas, or one zone that never seems to shut off. Our irrigation leak detection page covers what professional testing finds that a walkthrough misses.

Pools are the other Florida special: evaporation is normal, but an autofill valve stuck open or a structural leak can quietly add hundreds of gallons. Mark the waterline with tape, wait 24 hours with the pump running normally, and measure the drop — more than about a quarter-inch per day in normal weather deserves investigation.

Walk-Through: Signs of a Hidden Leak

While you’re at it, do a 10-minute walk-through:

• Stains or bubbling paint on walls and ceilings
• Soft or warped flooring, especially near bathrooms and kitchens
• Musty odors in closets, cabinets, or laundry areas
• Warm spots on the floor — a classic sign of a hot-water slab leak
• The sound of running water when everything is off
• Mildew where it shouldn’t be, like on a dry interior wall

Any of these plus a moving meter means the leak is real and concealed — time to stop DIYing and pinpoint it.

Plumber or Leak Detection Company?

This is the question homeowners ask most once the meter confirms a leak — and the answer matters. Plumbers fix known leaks. Leak detection companies find unknown ones.

• Call a plumber when you know where the problem is: a visibly leaking water heater, a toilet that needs rebuilding, a burst pipe you can see.
• Call a leak detection specialist when the meter moves but you can’t find the source — signs point under the slab, behind walls, or along the underground service line. Detection uses acoustic sensors, thermal imaging, and tracer gas to pinpoint the exact failure point.

Why it matters: a plumber without locating equipment has two options — exploratory demolition or guessing. Both cost you money, and unnecessary demolition can complicate an insurance claim. Get the pinpoint first, then hand the repair to whoever you like. Here’s how professional detection actually works.

What to Have Ready Before You Call

You’ll get faster, more accurate help if you have this ready:

• Where and when you first noticed signs (stains, sounds, bill spike month)
• Your meter test results — how much it moved and over what time
• Isolation test result — inside or outside?
• Photos of any stains, damage, or soggy areas, ideally time-stamped
• Your home’s age and pipe material if you know it

Will Your Water Utility Adjust the Bill?

Many Florida utilities offer a one-time leak adjustment or credit when you can show a leak was found and repaired — typically requiring a plumber’s invoice or repair receipt and sometimes a meter-reading history. Policies vary by provider and often limit adjustments to once per year or per property, so check with your specific water utility before assuming. Either way, document the repair: the same paperwork supports both the utility credit and any insurance claim.

Frequently Asked Questions

How do I check my water meter to tell if I have a hidden leak?
Shut off everything that uses water (including irrigation and ice makers), note the meter reading or watch the leak-indicator dial, wait 30 minutes without using water, and check again. Any movement means water is flowing somewhere it shouldn’t.

How much can a hidden leak actually add to my water bill?
It varies enormously — a running toilet can waste hundreds of gallons a day, while a pinhole slab leak may add a steady, smaller amount that compounds month after month. The meter test tells you the flow rate; multiply by your utility’s per-gallon rate for your actual cost.

Should I call a plumber or a leak detection company for a high water bill with no visible leak?
A leak detection company. Plumbers excel at fixing known problems; when the source is hidden, you need acoustic and thermal locating equipment first. Pinpoint the leak, then any plumber can do the repair.

Can a high water bill be caused by something other than a leak?
Yes — estimated meter reads, longer billing cycles, rate or tier increases, irrigation schedule changes, pool autofill issues, and extra household usage are all common non-leak causes. Always compare gallons across bills before assuming a leak.

How do I find a water leak between the meter and my house — and who pays for that repair?
Close the house main shutoff and watch the meter: if it still moves, the leak is in the service line. That line is the homeowner’s responsibility in most Florida utilities. Because it’s buried, professional acoustic locating beats exploratory digging.

My meter spins intermittently but I can’t find the leak — what next?
Intermittent movement often means a toilet flapper that seals sometimes, an irrigation valve sticking open on certain cycles, or a pressure-dependent pinhole. Run the dye check on every toilet, run each irrigation zone manually while watching the meter, and if it persists, get professional detection — intermittent leaks are exactly what acoustic equipment is for.

Will my water utility give me a credit for a leak?
Many Florida utilities offer leak adjustments with proof of repair, but rules, limits, and application processes differ by provider. Contact your utility directly, and keep your repair invoice and meter readings as documentation.

Next Step

A high water bill with a hidden leak behind it only gets more expensive the longer it runs. You’ve now got the full DIY diagnostic — meter test, isolation, toilets, irrigation. If the meter is still moving and the source won’t show itself, that’s exactly what professional locating is for. Learn more in our guide to finding an underground water leak, or reach out through our contact page to schedule an inspection.