Water or Gas Leak? How to Spot One, What to Do First, and How It Gets Traced

Most leaks in a house are water, not gas, and most of them are slow. A damp patch that keeps coming back, a boiler that needs topping up every week, a meter that never quite stops. Slow leaks are easy to live with for a while, which is the problem: the water is going somewhere, and by the time it shows on a ceiling it has usually been soaking into the floor or wall for some time.

This guide covers how to tell what kind of leak you have, what to switch off in the first few minutes, and how a leak is actually traced back to where it starts, which is often nowhere near where the water shows. It is written for homeowners and landlords across Kirklees and Calderdale, from our base at Hartshead.

Signs of a hidden water leak

Any one of these on its own is worth checking. Two together usually means a leak:

• A damp patch on a ceiling or wall that grows, or comes back after it dries
• The water meter still turning with every tap and appliance off
• Boiler pressure that keeps dropping and needs topping up
• A sound of running or hissing water when nothing is on
• Mould, peeling paint or a musty smell in one spot
• Floorboards or skirting that are swollen, or a floor that feels warm in a line
• A water bill that jumps without a reason

The meter test is the quickest way to be sure. Turn off every tap and anything that uses water, including the washing machine and any outside tap, then look at the meter. If the dial is still moving after a few minutes, water is escaping somewhere between the meter and your taps.

Boiler pressure that keeps dropping is a leak too

A combi or system boiler runs on a sealed heating circuit, and the pressure gauge on the front shows how full it is. If you are topping it up regularly, the water is leaving the circuit somewhere: a weeping radiator valve, a joint under the floor, the boiler itself, or the pressure relief valve letting water out through the pipe that runs outside.

Topping it up keeps the heating running, but it also keeps feeding fresh water into the system, and fresh water brings fresh oxygen. In West Yorkshire's soft water that means more corrosion and more of the black sludge that ends up in radiators and the boiler. A system that needs topping up is worth finding the cause of, not just refilling. If the boiler is losing pressure and has started locking out, that is a boiler repair job as much as a leak.

What to do first with a water leak

• Find the stopcock and turn it off. It is usually under the kitchen sink, sometimes where the supply comes in under the stairs or in a cellar. Turn it clockwise. If it will not move, do not force it; a seized stopcock is a common call, and a snapped one makes things worse.
• Keep water away from electrics. If water is coming through a ceiling near a light fitting or onto sockets, switch off at the consumer unit before going near it.
• Switch the boiler off if the water is coming from it or from the heating pipework.
• Take photos of where the water is showing and the pressure gauge reading. They help with the diagnosis, and with an insurance claim if it comes to that.

Many home insurance policies include what is called trace and access cover, for the cost of finding a hidden leak and getting to it. It is worth checking your policy before work starts.

How a leak gets traced

The skill in leak detection is not finding water. It is working out where the water started, because it rarely appears in the same place. Water runs along pipes, joists and the tops of ceilings before it finds a way through, so the stain in the living room can belong to a joint under the bathroom floor two metres away.

The work goes in order, from the cheapest answer to the most disruptive:

1. Which system is it? The meter and the boiler pressure settle whether the leak is on the mains supply, the heating circuit, or a waste pipe, which only leaks when something drains.
2. The likely places first. Valves, joints, the boiler, under sinks, behind the bath panel and around the toilet. A good share of leaks are found here without lifting anything.
3. Isolating sections. Closing off parts of the system in turn and watching whether the loss stops narrows a leak down to one run of pipe.
4. Opening up only where it needs it. Once the leak is pinned to one run, the floorboard or panel that comes up is the one over it, not half the room.

In older terraces and stone cottages, where pipework has been added to over the decades, the leak is often at the join between old and new. That is why we would rather spend the time tracing it than guess. Once it is found you get an explanation of the cause and one price for the repair before any work starts, with no hidden call-out fee.

Gas leaks: what to do, and what happens next

If you smell gas, or hear a hiss near a gas pipe or appliance:

• Do not use light switches, plugs, doorbells or anything that could spark
• Do not smoke or use a naked flame
• Open doors and windows
• Turn the gas off at the meter if it is safe to reach
• Get everyone out of the property
• Call the National Gas Emergency line on 0800 111 999 from outside

The emergency service will make the property safe, which may mean capping the supply. They do not usually repair the leak itself. A Gas Safe registered engineer then has to find it, repair it, and test the installation for tightness before the gas can be turned back on and the appliances used again. That is the part we do.

A gas smell is different from carbon monoxide, which has no smell at all. If you feel headaches, dizziness or nausea that ease when you leave the house, or a carbon monoxide alarm goes off, treat it as an emergency in the same way and call 0800 111 999.

Leak detection near you

Haydn is Gas Safe registered (number 962740) and based at Hartshead. Leak tracing, burst pipes and seized stopcocks are part of our plumbing work across the Spen Valley and beyond, including Liversedge, Roberttown, Hartshead, Heckmondwike, Cleckheaton, Mirfield and Brighouse. For a boiler that is leaking or has stopped, see emergency callouts.