Office water bill gone up? How to check for a hidden leak
When an office’s water bill rises but nothing about how the building is used has changed, the cause is usually a leak on the pipe outside, a leak inside, or several small faults together. A few meter readings, taken at the right times, show which.
Start with who pays for which meter
In a building with one occupier, there is usually one meter and one bill. In a multi-let office, the landlord may have the main meter and recharge water through the service charge, or each tenant may have a sub-meter or a separate supply for their floor. Before testing anything, ask the managing agent how the supply is split. If the rise shows on one sub-meter, the search starts in that tenant’s space; if it shows only on the main meter, the common parts and the pipe outside are more likely.
Compare a working day with a closed one
Offices use most of their water during working hours, so the useful reading is the one taken when nobody is in. Note the meter at the end of the day and again before the first person arrives, or take two readings half an hour apart at the weekend. Include the red dials or the last digits. If the small disc or star on the meter face is turning while the building is closed, water is being used or lost.
Some buildings have an automatic meter reader. If yours does, your water retailer may be able to provide interval data, which shows whether use ever drops close to zero at night. A flat line that never falls points the same way as a turning dial.
Find where the main comes in
The meter is usually in a small chamber under a cover in the pavement, the car park or a planted strip near the entrance. The internal stopcock sits where the main enters the building: often the plant room, a basement or riser cupboard, or near the ground-floor kitchen. Knowing where both are saves time on the day, because the engineer will ask for them first.
Close the stopcock: inside the building or underground?
With the building closed, shut the internal stopcock fully and watch the meter for ten minutes.
| With the stopcock shut | What it points to | Next step |
|---|---|---|
| The meter stops | Water is being lost after the stopcock: in pipework, cisterns, taps, plant or appliances inside the building. | Work through what uses water when the office is empty. |
| The meter keeps moving | Water is escaping on the supply pipe between the meter and the stopcock, usually under the car park or pavement. | Read about leaks under the car park below. Finding it needs listening or tracer-gas equipment. |
| The meter slows but keeps moving | There may be a loss on both sides, or the stopcock may not be closing fully. | Have the stopcock checked, then test again. |
What uses water in an office when nobody is there
A rising bill is more often a handful of small faults than one burst pipe. Check the things that can run without anyone touching them:
- Urinals. A cistern-fed urinal on a timer keeps flushing through the night and the weekend unless a flush control is fitted and working.
- WC cisterns. A fill valve or flush valve that passes sends a steady trickle into the pan or the overflow. Check the cisterns on every floor, including accessible and shower-room WCs.
- Tea points. Boiling-water taps, water coolers, dishwashers and ice machines plumbed into the supply, any of which can weep at the connection.
- Cold water storage. A tank whose float valve no longer shuts keeps refilling and spills through its overflow pipe.
- Heating plant. A pressurisation unit that tops up the heating every day, or a safety valve dripping into its tundish, the small open funnel beneath it.
- Air conditioning and humidifiers. Some units have their own water feed, and a valve that stays open can run unnoticed.
Isolate one suspect at a time and read the meter again. A drip of one a second adds up to roughly 15 litres a day, so several small faults across a few floors are worth finding.
Leaks under the car park
If the meter moves with the stopcock shut, the supply pipe is leaking somewhere between the meter and the building. Signs on the surface include water rising through paving joints, a patch of tarmac that stays damp or a strip of grass that stays green in dry weather. Often there is nothing to see. The pipe is located with acoustic listening, leak-noise correlation and tracer gas, and then exposed with a targeted excavation once the position is known. How ADI investigates water mains and car park supplies.
What a small leak adds to a quarterly bill
Meters read in cubic metres, and each cubic metre is 1,000 litres. A leak of 20 litres an hour comes to 480 litres a day. Over a quarter of 91 days that is nearly 44 cubic metres, all of it used while the office is shut.
When to call
Call if the meter keeps moving after everything you can find is off, if it moves with the stopcock shut, or if you would prefer an engineer to run the checks with proper equipment. Tell the office which readings you took and what changed; it shapes the quote and the plan for the visit.