A wet patch that stays soggy through dry weather usually means a leaking underground supply pipe. In Scotland, the pipe from the boundary to your home is yours, and most homes are unmetered, so the patch is often the only warning you get. Confirm it with the checks below, then have the leak pinpointed before anyone digs.
Wet Patch in the Garden or Driveway? Finding an Outside Leak
Every summer we get the same call. Someone has noticed a wet patch in the garden that never dries out, or a dark stain creeping across the driveway during a week without rain. They have watched it for a fortnight, hoped it was drainage, and now the lawn squelches underfoot.
Sometimes it is drainage. But a patch that stays wet through dry weather, especially one sitting over the line between your outside stopcock and your front door, points to a leaking supply pipe more often than not. This guide covers how to tell the difference, which checks you can do yourself, and how the leak gets found without your garden ending up in trenches.
What this guide covers
Why a patch that never dries matters
The pipe feeding your home carries mains water under constant pressure, day and night. Even a small split pushes water into the ground around the clock, so the soil never gets the chance to dry. Rain-soaked ground recovers in a few days of decent weather. A leak-soaked patch does not.
There is a Scottish twist that catches people out. Most households here pay for water through council tax rather than a meter, so a leak does not show up as a bigger bill the way it would in a metered English home (Scottish Water explains this here). With no bill to warn you, the ground itself is usually the first and only signal.
It is also worth knowing that this is not a problem you can park indefinitely. Under the Water (Scotland) Act, owners are legally obliged to repair leaks on their supply pipe. Scottish Water can serve notice, carry out the repair itself and charge the owner for the work, as Citizens Advice Scotland sets out. Finding the leak early keeps you in control of the timing and the cost.
Rule out the innocent causes first
Not every soggy corner is a leak. Before you spend money on detection, check the patch against the usual suspects.
| Possible cause | What it typically looks like | Quick test |
|---|---|---|
| Poor drainage after rain | A broad damp area in a low spot, whole lawn affected | Wait for a dry week. Drainage dampness fades; a leak does not. |
| Leaking gutter or downpipe | Wet strip against the wall, below the downpipe | Watch it during rain. Dry weather should dry it completely. |
| Natural spring or high water table | Seasonal wetness, worst in winter, often on sloping ground | Compare summer and winter. Springs usually ease off in dry months. |
| Leaking waste drain | Lush growth or odour near a drain run, wetness comes and goes | Drains only flow when you use water, so the patch fluctuates. |
| Supply pipe leak | Constant wet patch on the pipe route that never dries | Stays identical through dry spells. Grass over it often grows greener. |
The pattern to hold onto is consistency. Weather-driven dampness follows the weather. A pressurised leak ignores it.
Signs the wet patch in your garden is a supply pipe leak
The supply pipe normally runs in a fairly straight line from the boundary stopcock (usually a small metal or plastic lid in the pavement or at the edge of your property) to the point where the pipe enters the house. If your patch sits somewhere along that line, be suspicious.
Strong indicators of an outside leak
- The patch stays soggy after a week or more without rain
- It sits roughly on the line between the boundary stopcock and the house
- One strip of grass is noticeably greener or growing faster than the rest
- You can hear a faint hiss at the internal stopcock when everything is turned off
- Moss, algae or weeds thrive along one set of driveway joints
- Water trickles along the kerb or pools on the pavement outside in dry weather
Two or three of these together make a leak the most likely explanation. At that point the question stops being “is it a leak?” and becomes “where exactly is it?”, which is a very different job.
Checks you can do this afternoon
You do not need any equipment for a first pass. These three checks cost nothing and give a detection engineer a head start even if you end up calling one.
Step 1: Mark the patch and starve it
Push a couple of tent pegs or plant markers around the wet area and stop all garden watering. If the patch holds its size and sogginess through several dry days while the rest of the garden dries, the water is coming up from below, not down from above.
Step 2: Listen at the internal stopcock
Turn off every tap and appliance that uses water, then put your ear (or the handle of a long screwdriver) against the internal stopcock, usually under the kitchen sink. A steady hiss or rushing sound with everything off means water is moving through the pipe, and if nothing indoors is using it, it is escaping somewhere.
Step 3: Isolate the supply pipe
Close the internal stopcock fully. If the hiss at the pipe stops, the leak is on your side of the stopcock, indoors. If you can still hear flow at the boundary stopcock outside, or the patch keeps growing with the house isolated, the leak sits in the underground run between the boundary and the house.
If your home is one of the unmetered majority in Scotland, the classic advice about watching the meter dials will not work for you. We have written a separate guide on checking for a water leak without a meter that covers the alternatives in more depth.
Monoblock driveways hide leaks well
Scotland loves a monoblock driveway, and monoblock is unusually good at hiding leaks. The blocks sit on a bed of sharp sand, and escaping water spreads sideways through that bed long before it shows on the surface. By the time you see anything, the water may have travelled several metres from the actual split.
Watch for the indirect signs instead. Individual blocks that sink or rock underfoot, joints that stay dark while the rest of the driveway is bone dry, and lines of moss or weeds tracking across the surface all suggest water moving underneath. The wet corner you can see is a symptom, not a map reference.
This is exactly why we survey before anyone lifts a block. Lifting and relaying monoblock is skilled work, and relaying it twice because the first hole was in the wrong place is an expensive way to learn where the pipe runs.
Why digging on a guess costs more
A typical supply pipe run is somewhere between five and twenty metres. Digging “where it looks wettest” gives you a small chance of landing on the split first time, and every miss means another hole, more spoil, and more reinstatement of lawn, slabs or monoblock afterwards.
There is an insurance angle too. Most buildings insurance policies include trace and access cover, which pays for professionally locating a hidden leak and making good the access afterwards. MoneySuperMarket, citing Defaqto, puts it at 94% of policies, with typical limits of £5,000 to £10,000. Speculative DIY excavation is precisely what that cover exists to avoid, and we cover how it works in our guide to trace and access cover.
If you would rather not spend a fortnight watching grass dry and second-guessing hole locations, call us on 07700 152 467 and we will pinpoint the leak before a single spade goes in.
How outside leaks get pinpointed
Professional detection works in two stages. First the pipe route is traced and marked, so the survey follows the pipe rather than the puddle. Then the leak itself is located along that route.
On an outside leak the main tool is acoustic detection. A pressurised split makes a constant noise as water forces its way out, and a ground microphone picks that noise up through soil, slabs or monoblock. Moving along the marked route, the signal peaks directly over the leak.
On plastic pipes, which carry sound poorly, tracer gas does the job instead. A harmless hydrogen-nitrogen mix is introduced into the pipe, escapes at the split, rises through the ground and is picked up by a surface probe.
The result is a marked dig point a spade’s width across, rather than an open-cast mine in your front garden. If you want more detail on the wider process, our guide to finding an underground water leak walks through it start to finish.
Who owns the pipe under your garden (and who pays)
In Scotland the split of responsibility is clear. Scottish Water owns the water main in the street, the communication pipe from the main to your property boundary, and the boundary stopcock. The owner is responsible for the supply pipe from the boundary into the home, including every metre under the garden or driveway, plus all internal plumbing (Scottish Water sets out the boundary here).
So a wet patch inside your boundary is usually your pipe and your repair. If the wetness is out in the street or at the boundary stopcock itself, report it to Scottish Water instead. Flats and older terraced houses often share a single supply pipe, which makes responsibility joint with the neighbours (Scottish Water’s pipes FAQ covers this). Our article on who is responsible for water pipes in Scotland goes through each scenario in detail.
One helpful footnote: Scottish Water may offer an assisted supply pipe repair through its supply pipe repair policy in some circumstances, so it is worth asking when you report the leak.
Frequently asked questions
How do I tell if a wet patch is a leak or just drainage?
Watch it through a dry week. Dampness from rain or poor drainage shrinks and dries as the weather improves. A patch fed by a pressurised supply pipe stays the same size and sogginess regardless of weather, and the grass over it often grows greener and faster than the surrounding lawn.
Will a leaking supply pipe raise my water bill in Scotland?
Usually not. Most Scottish households are unmetered and pay for water through council tax, so the charge stays the same however much water escapes. That removes the early warning a metered home would get, which is why outside leaks in Scotland often run for months before anyone notices the ground.
Is the pipe under my garden my responsibility or Scottish Water’s?
Inside your property boundary, it is yours. Scottish Water owns the main and the communication pipe up to the boundary stopcock; the owner is responsible for the supply pipe from the boundary into the house, including under gardens and driveways, and is legally obliged to repair leaks on it.
Will my driveway need to be dug up to fix the leak?
Only a small section, if the leak is located properly first. Professional detection narrows the dig to a marked point roughly the size of a paving slab, and monoblock can usually be lifted and relaid over a hole that size without visible scarring. Guess-digging is what wrecks driveways.
Does home insurance pay for finding an outside leak?
Often, yes. Around 94% of buildings policies include trace and access cover according to MoneySuperMarket, citing Defaqto. It pays for locating the leak and making good the access, typically up to £5,000 or £10,000, though the pipe repair itself usually sits outside that cover. Check your policy wording first.
Related reading
- How to Find an Underground Water Leak (and Who to Call)
- How to Trace Underground Water Pipes Before You Dig
- Who Is Responsible for Water Pipes in Scotland?
MCR Leak Detection provides water leak detection across Scotland, from city driveways to rural supply runs.
Speak to MCR Leak Detection
A wet patch that will not dry deserves an answer, not a guess. We locate outside leaks non-destructively across Scotland, 24/7, and mark the exact dig point before any ground is broken.