How Much Is “Unusually High”?

Before diagnosing the cause, it helps to know what normal looks like. Water usage varies by household size and season — irrigation in summer, for example, will naturally push bills higher.

According to the U.S. Environmental Protection Agency, the average American family uses about 300 gallons of water per day indoors. For context, that’s roughly 9,000 gallons per month. A household of four in Sandy, UT with normal usage should land in a predictable monthly range. A jump of 20–30% or more above your historical average — without a seasonal reason — is worth investigating.

What we’ve seen in practice: most homeowners who call us about a high water bill have seen a 30–100% increase. That level of increase almost never has an innocent explanation. It points to a fixture problem or an active leak somewhere in the system.

The Most Common Causes of a High Water Bill

Here are the causes we find most often when investigating an unexpected spike in water cost. They’re listed roughly in order of how frequently we encounter them:

1. A Running Toilet

A toilet that runs continuously — even silently — is one of the most common causes of a spiked water bill. A toilet with a worn flapper or a stuck float valve can waste 200 gallons or more per day. That’s 6,000 extra gallons per month — which will show up clearly on your bill.

The tricky part is that some running toilets are silent. The water leaks from the tank into the bowl without making a sound. To check: put a few drops of food coloring in the tank. Wait 15 minutes without flushing. If color appears in the bowl, water is leaking past the flapper.

2. A Hidden Plumbing Leak

A hidden leak in a supply line — inside a wall, under the slab, underground between the street meter and the house — is the most serious cause of an unexplained high bill. Unlike a running toilet, which wastes water intermittently, a pressurized supply line leak runs continuously at full line pressure.

In our experience, a small pinhole leak in a pressurized pipe can waste 100–400 gallons per day depending on line pressure and the size of the failure point. A slab leak in a hot water supply line can waste significantly more. And because these leaks are hidden, they don’t just drive up water bills — they cause water damage, mold, and potentially structural problems if left unaddressed.

To find out if a hidden leak is the cause, see our guide on signs you may have a hidden water leak and the DIY meter test described there. For professional diagnosis, our water leak detection service in Sandy, UT uses electronic equipment to find exact leak locations without opening walls or floors.

3. Irrigation System Issues

Outdoor irrigation systems are a surprisingly common cause of high water bills — and one of the easiest to overlook, especially at the start of the season. A single broken irrigation head, a cracked lateral line, or a stuck open zone valve can waste thousands of gallons per month.

Many customers notice their bill goes up in spring when irrigation is turned on, but assume it’s just the normal seasonal increase. A sprinkler head spraying at full pressure for hours every day can easily double a water bill. Walk your yard and watch each zone run to check for obvious spraying, flooding, or puddling.

4. A Dripping Faucet or Fixture

A faucet that drips once per second wastes approximately 3,000 gallons per year. That sounds minor compared to a slab leak, but multiple dripping fixtures add up — and they’re easy to ignore because the drip rate is so slow. Check all faucets inside and outside the home, including utility sink faucets and hose bibs.

5. A Leaking Water Heater

Water heater leaks often go unnoticed because the unit is typically in a utility room, garage, or closet that isn’t checked frequently. A slow drip from the pressure relief valve, a leaking supply connection, or a failed tank can add significant water volume to your monthly usage without any obvious signs until damage appears on the floor.

6. A Malfunctioning Whole-Home Softener or Filter

Water softeners that are stuck in a regeneration cycle or set to regenerate too frequently can use hundreds of gallons per cycle. If you have a whole-home water treatment system, check its regeneration schedule and confirm it’s operating within the manufacturer’s recommended cycle frequency.

7. Seasonal and Occupancy Changes

A house guest staying for a month, a new teenager taking long showers, or a new appliance like a second refrigerator with an ice maker can all contribute to higher usage. These aren’t leaks, but they can explain a bill increase that seems otherwise mysterious. Rule these out before assuming a plumbing problem.

How to Diagnose the Cause Yourself

Before calling a plumber, you can narrow down the cause using a few simple tests. Here’s the approach we recommend:

1. Check every toilet — Use the food coloring test on each toilet tank. If color appears in the bowl without flushing, that toilet’s flapper is leaking. A running toilet is the easiest and cheapest fix on this list.
2. Do the water meter test — Turn off all fixtures and appliances. Watch the meter leak indicator. If it’s moving, you have an active leak somewhere in the system beyond the toilets.
3. Isolate indoor from outdoor — Shut off the main indoor valve and recheck the meter. If the meter stops, the leak is inside. If it keeps moving, the leak is in the underground line from the meter to the house.
4. Run your irrigation system zone by zone — Watch each zone for broken heads, misdirected spray, or pooling water. A zone that causes water to pool in a low spot may have a cracked underground lateral line.
5. Check your water heater — Inspect the area around the base of the unit and the supply connections for any dripping, staining, or moisture on the floor.

High Water Bill Causes: A Quick Comparison

Cause	Typical Daily Waste	Detectable Without a Plumber?	Urgency
Running toilet	200–400 gallons	Yes — food coloring test	Moderate
Hidden supply line leak	100–400+ gallons	Partially — meter test only	High
Slab leak	50–300+ gallons	No — requires professional detection	Very High
Broken irrigation head	50–200 gallons	Yes — visible during zone test	Moderate
Dripping faucet	5–20 gallons	Yes — visible drip	Low
Leaking water heater	Varies	Partially — check unit visually	Moderate–High

What To Do If You Can’t Find the Cause

If you’ve checked every toilet, inspected the irrigation system, examined visible fixtures, and done the meter test — and the meter is still moving with everything off — you have a hidden leak that cannot be found without professional equipment.

This is exactly what our leak detection plumber service is designed for. We use acoustic listening devices, thermal imaging cameras, and pressure testing to find the exact location of a leak — under slabs, behind walls, or underground — without opening up your home to search. Learn more about how this works in our post on how leak detection technology works.

Can You Get a High Water Bill Adjustment?

Many municipal water utilities — including Jordan Valley Water Conservancy District, which serves much of Sandy, UT — offer bill adjustments or credits for verifiable plumbing leaks. This typically requires documentation showing the leak has been repaired.

In our experience, having a plumber’s invoice showing the leak detection and repair is usually sufficient for a credit application. It’s worth calling your utility to ask about their policy once a leak has been confirmed and repaired. Most utilities have a formal process for this, and adjustments can reduce the inflated charges significantly.

Frequently Asked Questions