Hotel water bill gone up? How to check for a hidden leak

Before you start: find the meter and the stopcock

The water meter is usually in a chamber in the pavement or the car park, near the boundary. The internal stopcock is wherever the main enters the building, often in the plant room or a ground-floor cupboard. If nobody on site knows where either is, that is the first job, and it is worth doing before you have a problem: the guest house in one of our case studies lost the first hour of its survey to a meter nobody could find.

Larger hotels may have a bulk meter and sub-meters for the kitchen, the pool or a leisure block. Each one can be read the same way.

Step 1: read the meter when the building is at its quietest

Pick the quietest hour you have, typically between two and four in the morning, when no baths are running and the kitchen is closed. Read the meter, including the red dials or the last digits, and read it again thirty minutes later. Some meters have a small spinning disc or star that turns with any flow; if it is turning at 3am, water is moving.

If you have a smart or automatically read meter, ask the water retailer for the half-hourly data. A flat line overnight that never reaches zero is the same result in a graph.

Step 2: close the stopcock and read it again

Close the internal stopcock fully and watch the meter for ten minutes.

This is exactly the check our engineer ran at a detached hotel losing an estimated 17 litres an hour. The meter stopped, so the whole search moved indoors, where it found overfilling toilets, dripping taps and two plant-room leaks. Read that case.

Step 3: the usual culprits inside the building

Small faults are the most common cause of a rising bill in a hotel, and they hide in plain sight because each one looks harmless.

• Overfilling cisterns. Lift the lid on a few toilets; water trickling into the overflow or down the back of the pan is a fault. A few drops of food colouring in the cistern shows up in the pan within ten minutes if the flush valve is passing.
• Dripping taps and showers. One drip a second is roughly 15 litres a day; a hotel with forty bedrooms can have twenty of them.
• Urinal flush controls. Older cistern-fed urinals flush continuously unless the control is working.
• Plant. A pressurisation unit that tops up the heating every day, a safety valve dripping into its tundish (the small open funnel below it), a softener regenerating too often, a booster set that cycles when nothing is running.
• Pools and spas. Automatic top-up valves hide a pool leak completely. Turn the auto top-up off for 24 hours and watch the level.
• Kitchens and laundries. Recently installed appliances are worth a look; a new washing machine connection was one of the leaks at that detached hotel.
• Irrigation and outside taps. Timers left on from the summer, a garden tap somebody forgot.

Isolate each suspect in turn and watch the meter. When the meter slows, you have found one of them; when it stops, you have found the last.

Step 4: if the meter turns with the stopcock closed

The supply pipe is leaking somewhere between the meter and the building. Look along its route for anything green, soft or sunken, and for water surfacing on a path or in a car park, but do not expect to see much: an underground leak on a hotel supply can run for months without breaking the surface. Locating it is a job for acoustic listening, leak-noise correlation and tracer gas, and a targeted excavation once the spot is known. How ADI investigates mains and boosted supplies.

Turning the meter reading into litres

Water meters read in cubic metres. One cubic metre is 1,000 litres. A leak of 17 litres an hour, the estimate at that detached hotel, is about 400 litres a day and a little over 12 cubic metres a month, before anyone has had a shower. Small numbers on the meter are large numbers on the bill.