What a Hidden Leak Looks Like From Inside the House

A bill that moved without a reason

The most common first sign, and the least conclusive one. Bills move for weather, for visitors, for a new appliance, for a different number of days in the billing period and for a rate change.

Rule those out first, and then treat an unexplained rise as urgent rather than curious — because of the deadline, not because of the water.

Sound where there should be silence

Running, hissing or a faint rush when nothing is on. Stand still in the quietest part of the house late at night with everything off and listen at a wall or a floor.

Before you conclude anything, rule out the two innocent versions: a toilet passing water silently into the bowl, and a water heater or boiler topping itself up.

Heat, damp and movement

A warm patch on a floor where no heating runs is a hot line under it. Damp at the base of a wall, a section of lawn that stays green through a dry spell, or a paved area that is wet with no rain all point the same way. Mildew smell in a closed space is a slower version of the same signal.

Cracking or movement in a slab or a path is a late sign and a serious one, because by then water has been moving soil for a while.

Pressure that drops when it should not

A gradual loss of pressure at fixtures can be a supply leak, and can equally be scale, a failing pressure reducing valve, a partly closed valve or the utility’s own supply. It is a reason to test rather than a conclusion.

The one check that settles it

All of the above are circumstantial. The meter with everything off is not, which is why it is also the thing the adjustment schemes ask for.

• Proving it
• Whose pipe is it