# How to find a water leak underground | Notts Leak Detection > How to find a water leak underground: meter test, stop-tap test, walk the pipe route for signs, then acoustic or tracer gas location to pinpoint it. URL: https://nottsleakdetection.co.uk/guide/how-to-find-water-leak-underground/ 1. [Home](https://nottsleakdetection.co.uk/) 2. [Underground Water Leak Detection](https://nottsleakdetection.co.uk/underground-water-leak-detection/) 3. How to find a water leak underground Learn # How to find a water leak underground [Notts Leak Detection](https://nottsleakdetection.co.uk/) explains how to find a water leak underground: the checks you can do yourself to confirm it and narrow it down, and how professionals pinpoint it without digging. Published 28 September 2026 · Updated 28 September 2026 · By Notts Leak Detection **Short answer:** Start with the meter: turn off every tap, close the internal stop tap and watch the meter. If it still moves, the leak is on the buried supply pipe. Walk the pipe route looking for lush grass, damp patches or hissing. To pinpoint it without digging, professionals use acoustic ground microphones, leak noise correlation or hydrogen tracer gas. Knowing how to find a water leak underground starts with the meter. Most underground leaks never show on the surface, so the meter is the most reliable evidence you have. These steps confirm the leak and narrow it down. The last step is pinpointing it, which is where specialist kit comes in. ## Step 1: confirm it on the meter Severn Trent‘s [flow test](https://www.stwater.co.uk/help-and-contact/customer-information/metering-fixing-faults-policy/): turn off every tap, make sure no appliance is running, read the meter, use no water for three hours, then read it again. If the reading has gone up, water is escaping. The [BBC reported](https://www.bbc.co.uk/news/articles/c3d3772v7kro) a shorter version recommended by WaterSafe: read the meter half an hour after turning everything off, then again at least two hours later. ## Step 2: inside or outside? Close the internal stop tap, usually under the kitchen sink, and watch the meter for a few minutes. If it still moves, the leak is outside, on the buried supply pipe between the meter and the house. If it stops, the leak is inside the house. ## Step 3: walk the route The supply pipe runs from the boundary stop tap, in the pavement or at the edge of the drive, to where the pipe comes up into the house. It isn’t always a straight line. Walk it and look for the signs Severn Trent lists: - lush, greener grass during dry spells; - patches that stay damp; - a constant noise in the pipes when nothing is running. Confirmed it on the meter? Get the leak pinpointed before anyone lifts the drive. 0115 839 0791 (+441158390791) ## Step 4: pinpoint it This is where DIY usually stops. Professionals use: - Acoustic ground microphones, which listen through the surface for the hiss of water escaping under pressure. They work best on metal and lead pipe. - Leak noise correlation, where sensors at each end of the pipe time the leak noise to calculate its position. - Tracer gas, a non-flammable 5% hydrogen mix pumped into the drained pipe. It rises through soil, tarmac and paving, and a detector finds where it comes out. This is the method for quiet leaks on plastic pipe. The spot is marked on the ground, and the repair goes through one hole. See [underground water leak detection](https://nottsleakdetection.co.uk/underground-water-leak-detection/). ## What not to do Don’t dig trial holes along the route hoping to find it. The pipe is 750mm to 1,350mm deep, and each hole has to be filled and the surface put back. A hole in the wrong place tells you very little. Don’t ignore it either: a leak on a meter is billed every hour it runs, and the water company can require it to be fixed. If you are not sure whose side the leak is on, see [who is responsible for the water supply pipe](https://nottsleakdetection.co.uk/guide/who-is-responsible-for-water-supply-pipe/). ## Bottom line Confirm it on the meter, narrow it down by walking the route, then get it pinpointed before anyone digs. Random trial holes cost more to put back than finding the leak properly. Call 0115 839 0791 (+441158390791), 9am–7pm, 7 days. ## Questions people also ask ### Can I find an underground leak myself? You can confirm one and often narrow it down, using the meter and signs on the surface. Pinpointing it to one spot usually needs acoustic or tracer gas equipment, especially on plastic pipe. ### Why is there no wet patch? Water from a buried pipe often drains downwards instead of rising, especially in free-draining ground or under a hard surface. The meter is a more reliable sign than the surface. ### How deep is the supply pipe? It is laid 750mm to 1,350mm below finished ground level under the Water Supply (Water Fittings) Regulations 1999, although older pipes aren't always at that depth. Related service [Underground Water Leak Detection](https://nottsleakdetection.co.uk/underground-water-leak-detection/) Pinpoint a leak on the buried pipe between the boundary and your house with acoustic, gas and meter tests before anyone digs. [View service](https://nottsleakdetection.co.uk/underground-water-leak-detection/) Talk it through Lines open Monday–Sunday, 9am–7pm. 0115 839 0791 (+441158390791) ## More guides - [Decision Guide How much does leak detection cost in Nottingham?](https://nottsleakdetection.co.uk/guide/leak-detection-cost/) - [Decision Guide Is it a water leak or a faulty meter?](https://nottsleakdetection.co.uk/guide/water-leak-or-faulty-meter/) - [Learn Who is responsible for the water supply pipe?](https://nottsleakdetection.co.uk/guide/who-is-responsible-for-water-supply-pipe/) - [Learn How does the Severn Trent leak allowance work?](https://nottsleakdetection.co.uk/guide/severn-trent-leak-allowance/) - [Learn Can a water leak cause subsidence?](https://nottsleakdetection.co.uk/guide/can-a-water-leak-cause-subsidence/)