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Which Side Is Leaking
One of the few things about a slab leak you can often work out yourself, barefoot.
In one paragraph
A warm patch on the floor points to the hot line, which is close to diagnostic. Which side is leaking narrows where to look and frequently changes the repair, because the hot run and the cold run rarely take the same path beneath a slab.
The warm patch
A hot-water line leaking under a slab warms the concrete above it. On a tiled or wood floor in a cool house that is noticeable underfoot, and it points at a spot rather than a house.
It is the single most useful observation a homeowner makes on this subject, and it costs nothing but walking around without shoes on.
Why the side matters to the repair
Hot-water runs are generally shorter than the cold distribution, because they start at the heater rather than at the main. A shorter run is more often reroutable, and a reroute leaves the floor closed.
A cold-side leak upstream of everything is likelier to be on a main distribution run, and those are the ones where opening the slab is harder to avoid.
Proving it rather than guessing
Close the stop valve on the water heater and re-run the meter test. If the meter stops moving, the leak is on the hot side. If it carries on, it is not.
That is a ten-minute check with a definite answer, and it is worth doing before the visit rather than during it.
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If the meter moved with everything off, you have a leak.That is the finding worth leading with, because it saves an hour of diagnosis. We connect you with a contractor who covers your area, and your ZIP code is what decides who that is. You are never charged. It does not have to be a slab leak either — every kind of plumbing request is routed.
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