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High Water Bill in San Antonio? Find the Hidden Leak Before You Panic (SAWS Meter Test)

A water bill that jumped with no change in how you use water almost always means a silent leak. Here's the SAWS meter test, the dye-tab toilet check, and the one result that means it's under the slab.

Your bill jumped and your habits didn't. Start with the meter.

A SAWS bill that spikes with no change in how much water you use is almost never a billing error. It's water going somewhere you can't see, and the trick is telling a silent toilet from a pressurized line leaking under the slab, because one is a five-dollar part and the other is a job for acoustic detection. You can do most of that sorting yourself in about fifteen minutes with nothing but the meter in your yard and a few drops of food coloring. Armor Pro Services runs leak-detection calls across Bexar County every week, and we'd rather you rule out the cheap causes first than pay us to find a running toilet.

If you can already hear water running when every fixture is off, skip ahead to the slab section. That sound is the tell that matters most, and it changes what you should do next.

Why is my water bill so high in San Antonio?

A sudden high water bill with no lifestyle change points to a leak, and in San Antonio the usual suspects fall in a predictable order: a silent running toilet first, then an irrigation or hose-bib leak, then the water heater, and finally a pressurized underground or slab line. The last one is the expensive one, which is exactly why you work through the cheap causes before you assume the worst.

Here's the order we tell homeowners to check, cheapest and most common first:

1. A silent toilet leak. The single most common cause of a mystery bill, and the easiest to miss because it makes no sound and leaves no puddle.
2. Irrigation or an outdoor hose bib. A cracked sprinkler line or a valve stuck partly open runs water straight into the yard where you never see it.
3. The water heater. A weeping tank or a T&P valve dumping down a drain can add gallons a day without pooling anywhere obvious.
4. A pressurized underground or slab leak. The line under your yard or your concrete slab has failed, and water is escaping under full house pressure around the clock.

"After years of chasing high-bill calls under post-tension slabs across Bexar County, the pattern is clear: most turn out to be a toilet or irrigation, and the meter test tells us which camp you're in before we ever open a wall."

The good news is that one test at the meter separates the cheap problems from the expensive one. Do that first, and you'll know whether you're buying a flapper or booking a leak-detection appointment. Get a leak-detection appointment on the calendar if you'd rather we run the whole sequence for you.

How to check for a water leak with the SAWS meter

To check for a hidden leak with your meter, shut off every fixture and appliance that uses water, then watch the meter's low-flow leak indicator: if it keeps moving with everything off, you have an active leak somewhere in the system. This is the most reliable at-home leak test there is, and it costs you nothing but fifteen minutes.

Your SAWS meter sits in a rectangular box in the ground near the curb or the front sidewalk, usually under a metal or plastic lid you can pry up with a screwdriver. Once you have it open, work these steps in order:

1. Turn off everything that uses water. Faucets, the dishwasher, the clothes washer, the ice maker, and any irrigation zone. Don't flush a toilet during the test.
2. Find the leak indicator. On most SAWS meters it's a small triangular or star-shaped dial, or a tiny red or blue sweep hand, separate from the main odometer-style number wheels. It's designed to spin on the slightest flow.
3. Watch it for two full minutes. If that indicator is turning, creeping, or twitching with every fixture in the house off, water is moving through the meter and you have a leak.
4. Do the two-hour read if you want proof. Write down the full meter reading, leave all water off for one to two hours, then read it again. Any increase confirms water is escaping even with nothing running.

That one step, isolating the house valve, tells you whether you're chasing a yard leak, a house leak, or a utility-side problem before anyone starts guessing. Ready when you are: call 210-212-7667 and we'll walk the meter test with you on the phone.

The silent toilet leak dye test

The fastest way to catch a silent toilet leak is the dye test: put a few drops of food coloring in the tank, wait fifteen minutes without flushing, and if color shows up in the bowl, the flapper is leaking and letting tank water seep past into the bowl around the clock. A running toilet is the number-one cause of the mystery high bill we see, and it's a repair most homeowners can handle themselves.

Run the dye test on every toilet in the house, one at a time:

• Drop the dye in the tank, not the bowl. Ten to fifteen drops of food coloring, or a dye tab if you have one, into the water in the back tank.
• Wait fifteen minutes and don't flush. Walk away and let it sit. No flushing, no using that bathroom.
• Check the bowl. If the water in the bowl has taken on the color, tank water is leaking past the flapper or the flush valve seat. That toilet is your leak, or one of them.

A toilet that fails the dye test is usually a worn flapper, a flapper seat crusted with San Antonio's hard-water scale, or a fill valve set too high so water trickles down the overflow tube. Those are inexpensive parts and a manageable DIY fix. The reason this matters so much on the bill: a silent flapper leak runs continuously, day and night, and can quietly waste a couple hundred gallons a day without ever making the sound of a "running" toilet you'd normally notice.

"The homeowner is convinced it's a slab leak, we run the dye test, and the guest-bath toilet nobody uses turns the bowl blue in ten minutes. That's a good day. It's the cheapest possible answer to a scary bill."

If the dye test comes back clean on every toilet and the meter indicator is still moving, you've ruled out the most common cause, and it's time to check the water heater and the irrigation before you land on a slab leak.

Isolate the water heater and the irrigation

If the toilets pass the dye test but the meter is still spinning, isolate the water heater and the irrigation next, because both can leak gallons a day into places you never look. These are quick to rule out and they sit right between "cheap toilet fix" and "call for leak detection."

Start with the water heater. Close the cold-water shutoff valve on the line going into the top of the tank, then go back and check the meter's leak indicator. If it stops moving, the leak is on the water heater or the lines feeding it. A weeping tank, a dripping T&P discharge tube running to a drain, or a corroded supply connection can all add water use without ever pooling where you'd notice. That's a fixable repair, and a leaking water heater can spike the bill more than people expect when it's draining down a floor drain out of sight.

Next, the irrigation and outdoor spigots:

• Walk every hose bib and sprinkler valve for drips, hissing, or a soggy patch of lawn that stays wet when it hasn't rained.
• Check the irrigation controller for a zone that's stuck on or running longer than you set it.
• Look for a suspiciously green or sunken strip in the yard, which is a classic sign of an underground irrigation line leaking below the surface.

Irrigation leaks are common in San Antonio because the same expansive clay soil that shears copper supply lines also flexes buried poly and PVC irrigation pipe every time the ground swells and shrinks with the season. If the water heater's isolated, the toilets are clean, the irrigation checks out, and that leak indicator is still turning, you've reached the gate.

The gate: when the meter still spins with everything off

Here is the line that decides everything. If you've shut off every fixture, isolated the water heater, ruled out the toilets with the dye test, checked the irrigation, and the meter's leak indicator is still moving, you have a pressurized supply line leaking somewhere between the meter and your fixtures, and in a post-1970 San Antonio home that very often means under the slab. This is where the DIY sequence ends and detection begins.

Most homes south of Loop 1604 were built after 1970 on post-tension slab foundations, and that's the housing stock where under-slab supply leaks show up most. The reason is local: Bexar County sits on expansive clay over caliche and limestone that swells when wet and shrinks hard in drought, and that seasonal soil movement flexes and shears the rigid copper supply lines cast into the concrete. Add the high incoming pressure common off the SAWS main, which accelerates pinhole failures in copper, and slab leaks become a recurring category here, not a freak event.

"When the meter keeps spinning with everything off, that's an underground or slab leak, and the worst thing a plumber can do is open the concrete in the wrong place."

This is where you stop and call, because the next step is not something you can do yourself. Locating a pressurized under-slab leak takes acoustic listening discs that pick up the hiss of water escaping under the concrete and tracer gas, a safe helium-nitrogen blend pumped into the isolated line that rises through the slab at the exact leak point. On a post-tension slab that precision matters even more, because there are tensioning cables in the concrete that must never be cut. Guessing means a bigger hole, more floor to patch, and sometimes a repair in the wrong spot. This is exactly the work our slab leak repair crew does: if the meter keeps spinning with everything off, that's an underground or slab leak, and we pinpoint it within a few inches before any concrete is touched. Call 210-212-7667 and we'll tell you straight whether we can locate it today.

When it's NOT a leak, and we'll tell you so

Not every high bill is a leak, and we'd rather save you a service call than sell you a detection appointment you don't need. If you run the meter test and the leak indicator sits dead still with every fixture off, you do not have an active leak, full stop. No honest plumber should be talking about opening your floor when the meter isn't moving.

A few things get blamed on leaks that aren't:

• A one-time bill spike after filling a pool, running irrigation hard through a dry spell, or houseguests staying over. That's usage, not a leak, and next month's bill will settle back down.
• A SAWS rate or tier change that raised the cost per gallon without your usage changing at all. Check the bill's rate line, not just the dollar total.
• A damp baseboard after a hard rain, which is usually grading or drainage, not a pinhole under the slab.

If the meter's still and the bill still looks wrong, the next call is to SAWS about the reading or the rate, not to a plumber. We check the meter and isolate the system first precisely so you don't pay to jackhammer concrete over a problem that lives outside your plumbing. No upsell on faith.

FAQ

What are the signs of a slab leak with a high water bill?

The clearest signs of a slab leak are a high SAWS bill with no change in usage combined with the meter's leak indicator still spinning when every fixture is off. Beyond that, watch for the sound of water running when the house is silent, a warm or hot spot on a tile floor (which points to a leak on the hot-water side), an unexplained drop in water pressure, new cracks in tile or flooring, or a musty smell near a baseboard with no source above the floor. One clue homeowners miss: a leak on the cold-water side won't warm the floor, so people rule out a slab leak because "the floor isn't hot," when a cold-line pinhole is just as common. If the meter test confirms an active leak and you have any of these signs, that's a call for acoustic and tracer-gas slab leak repair at 210-212-7667.

How much water can a silent leak waste?

A lot, quietly. A silent toilet flapper leak can waste around 200 gallons a day without ever making a sound, and a small pinhole on a pressurized supply line under the slab can move thousands of gallons a month at full house pressure. That's why the bill jumps before you ever see water. The meter test and the dye test together will tell you which one you're dealing with in under twenty minutes.

Should I turn off my water if I think I have a hidden leak?

If the meter test shows an active leak and you can't isolate it to a fixture you can shut off individually, closing the main shutoff between periods of use will stop the water loss until it's repaired, and it protects the slab from soaking in the meantime. If you've isolated it to the water heater or a single toilet, just shut that fixture's valve and use the rest of the house normally. Either way, once you've confirmed the meter is moving with everything off, get it on the schedule. Call 210-212-7667 and we'll tell you whether it's a same-day pinpoint.

Get the leak found

If your SAWS bill jumped and your habits didn't, run the meter test first, then the dye test, then isolate the water heater and irrigation. Most of the time that sequence lands you on a cheap toilet or irrigation fix you can handle yourself. But when the leak indicator keeps spinning with everything off, that's a pressurized underground or slab leak, and it needs acoustic and tracer-gas location, not a guess and a jackhammer. We find it within a few inches before any concrete is cut, show you where it is, and price the repair upfront.

Armor Pro Services is licensed in Texas under RMP License #36282, locally owned and operated, and available same-day or next-day across San Antonio, Alamo Heights, Schertz, Converse, and Helotes. Free estimates and competitive, upfront pricing, with workmanship backed by a one-year written warranty and parts under manufacturer terms. Call us at 210-212-7667 or book slab leak detection and repair online.