A pipe you cannot see, under a floor you walk on
In a slab-on-grade house, the concrete floor sits directly on the ground, and the water supply lines that feed the kitchen, baths and water heater were often laid in the soil or gravel before the concrete was poured. Once the slab cured, those lines became part of the foundation for the life of the house.
Across Fullerton, a large share of homes went up in the 1950s, 60s and 70s as single-story tracts built this way. Most of those supply lines are copper; some older houses have galvanized steel. Either way, the pipe has been in place for decades, and every leak is the end of a long, slow process rather than a sudden event.
The usual contributors
| Factor | What happens to the pipe | Can you check it? |
|---|---|---|
| Age | Pipe walls thin over decades of water flow, especially at bends and joints. | Yes: the build year of the home is a starting point. |
| Hard water | Mineral content can contribute to scale and, combined with other factors, to wear inside the pipe. | Partly: scale on faucets and showerheads is a visible clue. |
| Abrasion | Pipe that touches concrete, rebar, rock or another pipe can rub thin as it expands and contracts. | No: only visible when the slab is opened. |
| Hot-water expansion | Hot lines heat and cool many times a day, so they move more than cold lines. | Indirectly: a warm floor points to the hot side. |
| Water pressure | Higher static pressure adds stress to every joint and thin spot. | Yes: a plumber can measure it with a gauge at a hose bib. |
| Soil movement | Settling or shifting soil can put strain on lines under and around the slab. | Partly: new floor or wall cracks are worth noting. |
| Installation details | Kinks, poorly made joints or pipe laid without protective sleeving where it passes through concrete. | No: original installation records are rarely available. |
Why hot-water lines often go first
Hot water moves pipe. Each time a tap opens, the hot line warms and lengthens slightly; when it closes, the line cools and shrinks. Over years, that movement can grind a pipe against whatever it touches inside the slab. Hot water can also be more aggressive inside the pipe than cold water.
That is why the classic slab leak complaint is a warm patch of floor somewhere between the water heater and a bathroom or kitchen. Cold-side leaks happen too, but they tend to be found by the water bill or the meter rather than by touch.
Factors you can check at home today
- Find the year your house was built on your property records or purchase documents.
- Look at faucet aerators and showerheads for white mineral scale.
- Note whether the house has had a slab leak before, and where.
- Look for a pressure regulator near where the main line enters the house, and ask a plumber to measure pressure if you are unsure.
- Check exposed pipe at the water heater and under sinks: reddish-brown or rough gray metal suggests galvanized steel; orange-brown or green-tinged metal suggests copper.
- Write down any new cracks in tile or along walls, with dates.
Key points
- Most common setting
- 1950s to 1970s slab-on-grade tract homes
- Typical pipe
- Copper, sometimes galvanized steel
- Line most often blamed
- Hot-water supply
- One cause or many
- Usually several together
- Who confirms the cause
- A licensed plumber, at the leak site
Questions to ask once the leak is found
- What did the pipe look like at the leak: thin overall, rubbed on one side, or failed at a joint?
- Does what you saw suggest the rest of the line is in similar condition?
- Is our water pressure within a normal range, and would a regulator help?
- Does this change which repair you would recommend?
Common questions
Does hard water cause slab leaks?
It can contribute, but it is rarely the only factor. Age, pipe movement, abrasion against concrete and water pressure usually play a part as well.
Can a newer home get a slab leak?
Yes. Leaks are more common in older homes, but installation details, pressure and soil conditions can cause leaks in newer slabs too.
Will fixing one leak stop future leaks?
It fixes that spot. Whether more leaks are likely depends on the condition of the rest of the line, which is worth asking the plumber about at the time of repair.
General information for Fullerton, not a quote or professional advice. In an emergency, call 911.