How to Spot a Hidden Water Leak Early in a Delhi Flat

1. The overnight test: does the flat use water when nobody does?

This is the single most useful leak check, and it works in a Delhi flat even without a per-flat water meter, because it uses the tank instead.

• If you have a water meter, close every tap, switch the geyser off and note the reading last thing at night. Read it again before anyone uses water in the morning. Any movement at all with nothing running means water is escaping somewhere between the meter and your fittings.
• If you do not have a meter, use the overhead tank. At night, after the tank has filled, switch the pump off at the MCB so it cannot refill, and mark the water level inside with a marker or a piece of tape. Check it before anyone uses water in the morning. A tank that has dropped noticeably overnight with nobody using water is telling you something leaks — and the commonest culprit is a WC flush valve seeping continuously into the pan.
• The WC dye check. Put a few drops of food colouring or a little coloured liquid into the cistern and do not flush. If colour appears in the pan within twenty minutes, the flush valve is leaking. A silently running WC wastes more water than every dripping tap in the flat combined, which matters a great deal when supply runs only a few hours a day. Our toilet flush guide covers what to do about it.
• Listen at night. With everything off and the flat quiet, stand near the bathroom wall. A faint continuous hiss or trickle inside a wall is a pressurised pipe leaking, and it is worth acting on immediately.

2. Learn what an early leak looks like

A hidden leak announces itself indirectly, and usually months before anything drips. Walk the flat once a month and look for these.

• Paint bubbling or blistering in one small area, particularly low on a wall shared with a bathroom or kitchen. Damp from a leak works upwards from the source; blistering in a defined patch is a strong sign.
• Skirting, wardrobe bases or a kitchen cabinet plinth that has swollen or softened. Board swells long before anything looks wet.
• A cool or slightly damp patch on the reverse side of a bathroom wall. Feel it with the back of your hand. This is often the first physical sign, and it appears in the bedroom, not the bathroom.
• Grout going dark or crumbling in one spot, especially where the bathroom floor meets the wall, or a floor tile that sounds hollow when you tap it.
• A white powdery bloom on plaster. That is salt carried out of the masonry by moisture, and it means water has been moving through the wall for a while.
• A musty smell in a cupboard or a corner that does not go away with ventilation.
• Falling water pressure with no other explanation, or a pump that starts more often than it used to.

3. Look under and behind things, once a month

Most leaks that get expensive start somewhere perfectly visible that nobody looks at. Five minutes with a torch and a piece of dry newspaper.

• Under both basins. Dry everything, lay a sheet of newspaper on the cupboard floor, and check it a day later. Paper shows a slow drip that a cloth-wipe test misses.
• The flexible connector hoses feeding taps, the WC and the washing machine. These are the most common sudden failure in a modern flat. Look for rust spots, a bulge, or fraying in the braiding, and replace one that shows any of those rather than waiting.
• Behind and under the washing machine, including the inlet valve and the drain hose end.
• The geyser and the wall under it. A stain on the wall below a geyser is an early warning — our geyser leaking guide covers what each leak point means.
• The WC base. A permanently damp ring or discoloured grout around the pan means the seal is going.
• The water purifier and its tubing, which is thin, push-fit and easy to knock loose when reaching into a cupboard.
• Around the overhead tank, for a steady overflow drip. A stuck float valve overflows quietly for weeks and soaks a terrace or a wall while it does.

4. In monsoon, decide first whether it is a leak at all

From July onward, damp patches in Delhi have two possible parents and the repairs are completely different. Sorting this out first saves paying the wrong trade.

• Track the rain. Note the date the patch appeared and whether it grew during rain. Damp that only worsens when it rains is seepage from outside; damp that grows steadily in dry weather is plumbing.
• Look at the position. A patch on an external wall, in a corner, near a window, or spreading down from the top of a wall points outside. A patch under an upstairs bathroom or beside a concealed pipe run points to plumbing.
• Do not repaint until it has been dry for weeks. A Delhi slab holds moisture long after the source is fixed, and paint over a damp wall peels within months.
• Clear the balcony and terrace drains before the season, because an overflowing outdoor drain is one of the commonest causes of internal damp that gets blamed on plumbing.

Our seepage and waterproofing guide covers telling these apart in detail, and if the damp is on your ceiling, our ceiling leak guide covers finding the source and raising it with the flat above.