Why Did My Water Bill Spike? What to Check Before You Panic

An unexpectedly high water bill is usually trying to tell you something. Here's how to figure out what.

I'm Justin Sims, and I get calls every month from homeowners in the Austin Hill Country who opened their water bill and nearly fell over. Some bills come in at two, three, even ten times normal. It's alarming—and it should be, because a sudden spike almost always means water is going somewhere it shouldn't.

Let me help you track down the problem.

First: Rule Out the Obvious

Before you start tearing apart your plumbing, check a few simple things:

Billing Changes

• Did you change from monthly to bi-monthly billing (or vice versa)?
• Did the utility estimate your previous bill and true-up this month?
• Are there new rate increases or tiered pricing you didn't know about?
• Did you have any billing corrections from previous periods?

Seasonal Factors

• Did you fill a pool or hot tub?
• Was there a heat wave that increased lawn irrigation?
• Did you have houseguests who increased water usage?
• Did you power-wash the deck or driveway?

If none of these explain the spike, you probably have a leak.

How to Confirm You Have a Leak

Here's a simple test that takes five minutes:

1. **Turn off all water in your home.** Everything—faucets, ice makers, irrigation, appliances.
2. **Find your water meter.** It's usually in a box near the street.
3. **Check the flow indicator.** Most meters have a small triangle, star, or dial that spins when water is flowing. If it's moving with everything off, water is going somewhere.
4. **Record the meter reading.** Write down the numbers.
5. **Wait 30 minutes** (still with no water use).
6. **Check the reading again.** If the number changed, you have a leak.

**How much water are you losing?** The difference between readings, multiplied by 48, gives you a rough idea of gallons lost per day.

The Usual Suspects: Where Leaks Hide

Toilets (The #1 Culprit)

Toilets account for more hidden water waste than anything else. A running toilet can leak 200+ gallons per day—that's 6,000+ gallons a month—without making any obvious noise.

The Dye Test:

1. Remove the tank lid
2. Drop in a few drops of food coloring or a dye tablet
3. Wait 15 minutes WITHOUT flushing
4. Check the bowl

If you see color in the bowl, the flapper is leaking. It's allowing water to constantly seep from tank to bowl, and your fill valve is constantly running to replace it.

Common toilet leak causes:

• Worn flapper valve (cheap, easy fix)
• Stuck or failing fill valve
• Float set too high (water drains into overflow)
• Cracked overflow tube

**Do this for every toilet in your house.** I've found many homes with multiple leaking toilets.

Irrigation Systems

Sprinkler systems are notorious for hidden leaks, especially here in Central Texas where the soil expands and contracts with our weather swings.

Signs of irrigation leaks:

• Soggy or unusually green spots in the lawn
• Water bubbling up when the system runs
• Low pressure at some sprinkler heads
• Unusually high bills during watering season

How to test:

1. Turn off the irrigation system at the controller
2. Run your meter test again
3. If the leak stops with irrigation off, the leak is in your sprinkler system

Irrigation leaks can be anywhere in the system—broken heads, cracked pipes, failed valves, or damage from lawn equipment.

Water Heater

Check around your water heater for:

• Pooled water at the base
• Moisture on the floor
• Corrosion or rust streaks
• Dripping pressure relief valve

A slow water heater leak can waste hundreds of gallons before you notice standing water.

Under-Slab Pipes (Slab Leaks)

This is the big one that homeowners dread. If the pipes running under your concrete slab develop a leak, water can flow for weeks before you see any sign.

Warning signs:

• Warm or hot spots on the floor
• Sound of running water when nothing is on
• Cracks appearing in foundation
• Moisture or mildew smells
• Water bill spike with no visible leak

Slab leaks are serious. They can cause foundation damage and require professional detection and repair.

Service Line

The pipe running from your meter to your house (the service line) is your responsibility, and it's buried underground where leaks aren't visible.

Signs of service line leak:

• Soggy area between meter and house
• Green grass stripe in dry season
• Meter shows flow but house shut-offs stop nothing

Faucets and Fixtures

A dripping faucet wastes 5-10 gallons per day. A steady drip can waste even more. Check:

• Kitchen and bathroom faucets
• Bathtub faucets (even if you mostly use the shower)
• Outdoor hose bibs
• Utility sink faucets

Hidden Pipe Leaks

Pipes in walls, ceilings, and crawl spaces can leak for extended periods before you notice.

Signs:

• Water stains on ceilings or walls
• Peeling paint or bubbling wallpaper
• Mold or mildew smell
• Warped or damaged flooring

Calculating the Cost

Here's some math that might motivate you to find that leak quickly:

Austin Water typically charges around $0.005-0.01 per gallon (varies by tier and usage). Doesn't sound like much—until you do the math:

• **Dripping faucet (1 drop/second):** ~5 gallons/day = 150 gallons/month
• **Running toilet:** 200+ gallons/day = 6,000+ gallons/month
• **Small pipe leak:** 10-50 gallons/hour = 7,200-36,000 gallons/month
• **Irrigation line break:** can be hundreds of gallons per hour

That "small" running toilet could add $30-50 to your monthly bill. A pipe leak could add hundreds.

What to Do When You Find a Leak

If It's a Toilet

Replace the flapper (usually under $10 at any hardware store). If that doesn't fix it, the fill valve might need replacement. Both are DIY-friendly repairs.

If It's a Faucet