Most Poway houses built on a slab have water lines running through or under that slab. Many have drain lines under it too. When one of those pipes leaks, you don’t see a puddle. You see a bill. Or a warm spot on the floor. Or a crack that wasn’t there last year.
On sandy ground, a leak like that mostly wastes water. On clay, it’s a foundation issue too. Here’s the straight version.
Why clay makes a leak worse
Clay soil swells when it gets wet. It shrinks when it dries. That’s the whole problem in one line.
A slab sits on that soil. When the whole lot gets wet and dries evenly, the slab moves a little, evenly. A leak does the opposite. It soaks one spot, constantly, for weeks or months. That spot swells. Or, on some soils and fills, it softens and settles. Either way, one part of the slab now moves differently from the rest.
That’s why the California Residential Code treats expansive soils as their own category. It says foundations and slabs on expansive soils are to be designed under a specific section of the California Building Code. A design like that assumes the moisture under the slab behaves more or less like the moisture around it. A steady leak breaks that assumption. Our page on expansive soil foundation repair has more background.
Test your meter. Today.
You don’t need a plumber to find out if water is leaving the system. You need your meter and fifteen minutes.
The City of Poway lays out the test:
- Make sure no water is running anywhere.
- Turn off faucets and water-using appliances, including the ice maker and any evaporative cooler.
- Read the meter. Write it down, including tenths of a cubic foot, or mark the needle with a felt pen.
- Read it again after 10 to 15 minutes.
If the reading changed or the needle moved, you have a leak somewhere. That’s the City’s rule, and it’s a good one.
EPA’s WaterSense program suggests a longer version: check the meter before and after a two-hour period when no water is used. Same idea, more sensitive.
A moving meter doesn’t tell you where the leak is. It could be a toilet flapper. Poway’s own page calls toilets the most common cause of high bills. So rule those out first with the food-coloring test the City describes. If toilets, faucets and irrigation are all quiet and the meter still moves, look harder.
Signs that point under the slab
These don’t prove an under-slab leak. Together, they make it worth checking:
- The meter moves with everything off and toilets ruled out.
- A floor spot feels warm. That points to a hot-water line.
- You hear water running when nothing is on.
- Flooring lifts, cups or smells musty in one area.
- New cracks in tile or drywall in one part of the house.
- Damp soil or efflorescence along one stretch of the slab edge outside.
- A sudden jump in the bill with no change in habits.
The City lists a broken service line at 15 gallons per minute as wasting 21,600 gallons in a single day. Even a slow leak, running for months, puts a lot of water into the same patch of clay.
Who owns the pipe
This trips people up. Poway’s water service code is clear. The City’s responsibility ends at the customer handle connected to the meter. Everything on the customer’s side, including the service line, is the customer’s to install and maintain. The code also says customers have to keep their service line and equipment in good repair and free from leakage at their own expense.
So a leak between the meter and the house, or under the house, is yours to fix. Call the City’s customer service line if your bill spikes. They can help you read the meter and understand the bill. The fix itself is on the property side.
The right order of operations
This is where people go wrong. They fix the crack first. Don’t.
First, stop the water. Find the leak and repair or reroute the line. A licensed plumber with leak-detection tools is the right call here.
Second, let the ground settle down. Soil that has been soaked for months doesn’t return to normal overnight. Some movement may continue for a while as it dries.
Third, document. Photograph cracks with a tape in frame. Note door gaps. Check floors for slope. Do it again over the following months.
Fourth, evaluate the foundation. Once the water is off and you have a few data points, you know whether the slab is still moving.
Fix the structure before the water and you may be fixing it twice. Our post on what over-irrigation, pools and leach lines do covers the other water sources that cause the same trouble.
Do and don’t
Do run the meter test a couple of times a year.
Do fix toilet and faucet leaks right away. They’re easy and cheap.
Do keep a record of the leak repair: date, location, what was done. You’ll want it later.
Don’t ignore a warm spot on the floor. Hot-water lines run under a lot of Poway slabs, and a warm patch is one of the few clues you can feel with your bare feet.
Don’t patch slab cracks before the leak is fixed.
Don’t assume a reroute fixed everything. Keep watching the cracks for a season.
What a foundation look adds
After a leak, a foundation evaluation answers a few specific questions. Did the slab move? Where? Is it still moving? Does the pattern match the leak location, or is something else going on, like fill settlement or drainage? Our slab foundation repair page explains the usual approaches.
Scope and cost depend on how big the affected area is, whether movement has stopped, the soil type, access inside the house, finish flooring that has to come up, and whether engineering is needed. When the findings call for design work, the plan should coordinate with licensed engineers as needed. Repairs to a structure in Poway generally need a building permit.
We cover the whole City of Poway. If your meter moved and your floor cracked, request a Free Quote. Bring the plumber’s notes. They help.