A doubled water bill in Addison or North Dallas usually means one of these seven things. Work down the list.
1. Running toilet
The #1 cause of high bills. A single toilet with a bad flapper can dump 200 gallons a day without you noticing. To check: put a few drops of food coloring in the tank. Wait 20 minutes without flushing. If color appears in the bowl, replace the flapper.
2. Irrigation leak
An underground irrigation line break can waste hundreds of gallons before the wet spot shows. Walk your yard the morning after a full system run. Look for boggy spots or "greener than the rest" grass.
3. Old / running softener
A softener stuck in regen dumps a lot of water. Check the salt level and the regen cycle counter.
4. Pool auto-fill
If you have a pool with an auto-fill float, a failed float sends water in continuously.
5. Slab leak
A pinhole leak in an under-slab supply line is the scariest cause because you often cannot see it. Warm spots on the floor, mildew smell, or a slight hiss under the concrete are the tells.
6. Water heater T&P valve leak
A T&P valve trickling into a drain pan can waste a lot of water — it often flows into a drain you never see.
7. Hidden wall or ceiling leak
Water bill up + drywall stain + no visible fixture leak = pipe in wall. Time for electronic leak detection.
The meter test — how to isolate
Every home has a water meter with a small triangle or dial that spins when water is flowing.
- Turn off every fixture and appliance in the house
- Look at the meter — is the small dial spinning?
- If yes, you have a leak somewhere
- Now shut off the water heater cold-inlet valve. Re-check the meter.
- If the dial stops, the leak is on the hot side. If it keeps spinning, cold side.
- Then shut off individual fixture branches one at a time and re-check
When to call for detection
If the meter test confirms a leak but you cannot find it in the seven-item list above, you almost certainly have a hidden leak — in a wall, above a ceiling, or under the slab. Electronic detection finds it without random demolition.
Addison / North Dallas — the hot-water slab leak
Expansive clay + hard water + 30+ year old copper = the classic Addison / Dallas slab leak profile. If your home was built before 1990 and you have any of the symptoms above — warm floor spot, mildew smell, hissing — call leak detection. Fast diagnosis saves the flooring.
Visual playbook
Belt Line Plumbing expert insight
This guide reflects what our licensed Texas RMP plumbers see on real core-service calls across Addison, Farmers Branch, Carrollton, and the greater Dallas North Tollway corridor. Belt Line Plumbing Co. has served the Addison area since 2007, with 412+ five-star reviews from north Dallas homeowners, property managers, and Belt Line Restaurant Row operators.
Local factors that affect the advice above: North Texas expansive clay soil drives most residential slab and sewer failures; Dallas Water Utilities supply water at 8–11 grains of hardness per gallon shortens every water heater and tankless system without a softener; and the February 2021 Winter Storm Uri freeze exposed attic supply lines across almost every 1970s–2000s Addison home. If your situation includes any of these local realities, factor them in before deciding between repair, replacement, or a preventive upgrade.