The best
cable detectors,
for drilling without drama

A fair amount of my work involves making holes in other people’s walls. A retrofit assessment under PAS 2035 often needs a cavity inspection hole to confirm what’s actually in the wall — the drill for that job has its own guide, and the borescope that goes in afterwards another. Before any of that happens, there is a duller and more important step: working out what is already buried in the wall, because a 240-volt cable and a 15mm copper pipe both object strongly to a masonry bit.

The honest framing is that no detector makes a wall safe. British walls are a century of improvisation — 1960s rewires that wander diagonally, gas pipes chased into plaster, extensions wired by someone’s brother-in-law. The wiring regulations (BS 7671) define “safe zones” where concealed cables are supposed to run: vertically or horizontally in line with a switch or socket, and within 150mm of the top of the wall or an internal corner. Trades treat those zones as places to be extra careful, not as a map of where cables are. A detector narrows the odds. Isolating the circuit closes them.

So this guide covers the indoor half — wall scanners, pipe and cable detectors, tracers — and finishes with the outdoor half: the cable avoidance tools (CAT scanners) used before anyone puts a spade near buried services.

The one I’d buy

Bosch D-tect 120 Professional

The sensible top of the range for building work: a radar-based scanner rather than a simple metal-and-mains sniffer, which means it can find plastic pipes and timber as well as cables and metal, and it keeps working on damp masonry where capacitive detectors give up. Owner feedback is consistent that it’s the point where results stop being a coin toss on real walls.

Typically £220–£300

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How I judge a cable detector

What it actually senses. There are two technologies here and the price gap between them is the whole story. Cheap and mid-range detectors combine a magnetic/inductive sensor (finds metal) with an AC field sensor (finds energised cables). Radar scanners — the Bosch D-tect family — bounce a signal off anything with different density to the wall, which is how they find plastic pipes, voids and timber that the cheaper technology is physically blind to. If a job involves plastic plumbing, and most modern British plumbing is plastic, only radar has a chance.

Honesty about live cables. An AC sensor only sees a cable that is energised and, ideally, carrying load. A lighting circuit with the lights off, a cable on a switched-off ring, a broken neutral — all quiet. Good detectors say this plainly in the manual; bad ones let you believe a green light means an empty wall. Whatever the tool, the discipline is the same: signal or no signal, treat the wall as live until the circuit is proven dead.

Behaviour on British walls. Detection depths are measured in laboratory block. Real walls are damp lime plaster, dense concrete block, dot-and-dab board with voids behind it, and foil-backed plasterboard that blinds every detector made. A tool that calibrates quickly, and re-calibrates when the wall changes, matters more than a headline depth figure.

A readout you can act on. A traffic light and a beep that strengthens towards the target is genuinely useful. A centimetre figure to one decimal place, on a £30 capacitive detector, is theatre. The best interfaces say: something is here, roughly this deep, possibly live — and admit when they don’t know.

Marking and repeatability. Finding a cable once is no use if you can’t find it again with a pencil in your hand. A marking hole or notch in the housing, a hold function, and a reading that repeats when you re-scan the same line are what separate instruments from novelties.

The comparison

The picks in detail

01

Bosch D-tect 120 Professional

Best overall — radar detection at a working price, and my top pick above

The D-tect 120 is where wall scanning stops being guesswork about metal and mains and starts being detection of objects. Its radar sensor picks up ferrous and non-ferrous metal, live cables, timber and — the big one — plastic pipes, with stated depths of around 120mm for metal and 60mm for cables and plastic. It has dedicated modes for masonry, drywall and (usefully for anyone drilling recent extensions) damp concrete, and calibration is automatic. Published user feedback is consistent on the two things that matter: it finds what cheaper detectors miss, and it false-alarms far less on dense or damp walls.

For anyone whose drilling carries consequences — fixing into unknown walls weekly, or opening cavity inspection holes — the gap between this and a £40 detector is the gap between a screening tool and an instrument.

For

• Radar sees plastic pipes, timber and voids, not just metal and mains
• Works on damp masonry and fresh concrete where capacitive tools misread
• Simple traffic-light interface with a marking aid — no menus to fight

Against

• Several times the price of a consumer detector
• No depth readout or live/non-live discrimination — that’s the 200 C’s job

Typically £220–£300

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02

Bosch D-tect 200 C Professional

The professional pick — when you need depth figures and live/non-live discrimination

The flagship. Radar to a stated 200mm, a colour screen that shows objects in the wall with an estimated depth, and — genuinely rare — the ability to distinguish live from non-live cables. It has view modes for spot checks and for sweeping larger areas, and stores results, which suits anyone producing evidence rather than just avoiding a bang. It’s the class of tool M&E contractors buy, priced accordingly.

Hard to justify against the D-tect 120 unless post-tensioned slabs, screeds full of underfloor heating, or dense concrete are a regular part of the week. When they are, nothing else on this page competes.

For

• Deepest detection here, with an actual depth estimate
• Distinguishes live from dead cables — almost nothing else does
• Object view across a scanned area, results can be saved

Against

• Serious money — trade pricing for trade risk
• Overkill for domestic stud-and-plasterboard work

Typically £620–£750

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03

Bosch GMS 120-27 Professional

Best mid-range — the trade standard for metal, studs and live cables

The successor to the GMS 120 that has rattled around British vans for a decade. It’s the conventional technology — inductive metal sensing plus an AC field sensor — done properly: steel to a stated 120mm, non-ferrous metal to about 80mm, live cables to about 50mm, timber studs to about 38mm, with separate modes for each and a centre-marking aid plus a pen supplied in the sleeve. Owner feedback says what it has always said about this line: excellent on metal, dependable on energised cables, and prone to enthusiasm on damp plaster if you skip the calibration — which is the physics, not the tool.

It cannot see plastic pipe and never will. Know that, and it’s the best £90-ish detector going.

For

• Strong, repeatable metal detection at trade depth
• Dedicated modes rather than one vague “scan”
• Robust housing, marker aperture, sensible price

Against

• Blind to plastic pipes and dead cables
• Needs re-calibrating as wall build-up changes, or it grumbles

Typically £85–£105

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04

Bosch UniversalDetect

Best for careful DIY — a detector that explains itself as you use it

The green-line detector for people who don’t use one every week, and its best feature is the screen: step-by-step prompts that tell you how to calibrate, how fast to sweep and what the reading means, which addresses the real failure mode of consumer detectors — user error. Stated depths are respectable for the class: magnetic steel to about 100mm, live cables to about 50mm, timber to about 25mm. Published feedback rates it clearly ahead of the anonymous £25 multi-scanners for consistency, with the usual honest caveats about plasterboard adhesives and foil backing confusing any capacitive tool.

For

• Guided operation — hardest detector here to use wrongly
• Sensible depth claims it can actually meet
• Detects steel, copper, live cable and timber studs

Against

• No plastic pipe detection
• Not far off GMS 120-27 money without the trade depths

Typically £70–£85

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05

Bosch Truvo

Best on a budget — one button, honest lights, from a brand with a reputation to lose

If the budget is £40, buy this rather than any of the feature-festooned anonymous scanners at the same price. One button, automatic calibration, a column of LEDs and a beep: metal to a stated 70mm, live cables to about 50mm. That’s the entire feature list, and the restraint is the point — no fake depth figures, no seventeen modes, nothing to set wrongly. Owner feedback is that it does what it claims on ordinary plasterboard and brick, and gets confused in the same places everything capacitive does. For hanging shelves and televisions without drama, it’s the honest floor of the market.

For

• Genuinely simple — nothing to misconfigure
• Claims modest depths and meets them
• Pocket-money insurance against a £300 call-out

Against

• No stud-finding mode for timber; metal and live cable only
• Coarse resolution — finds the cable, not its centreline

Typically £35–£45

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06

Zircon MetalliScanner m40

Best metal specialist — tracing pipe runs, rebar and lost fixings

A different tool for a different question. The m40 detects nothing but metal — magnetic to a stated 100mm, non-magnetic to about 50mm — and that single-mindedness makes it better at metal than the multi-function detectors: it will follow a buried copper heating pipe across a floor, map rebar in a slab before coring, or find the steel fixings that locate battens under render. Wide-scan for sweeping, pinpoint for the exact spot, LEDs that ramp with signal strength. It has no live-cable mode at all, which at least removes the temptation to trust one; pair it with a voltage stick and circuit isolation like everything else here.

For

• Excellent at the one job — deep, repeatable metal location
• Pinpoint mode finds screws and nails, not just pipes
• Light, cheap, runs for ages on a 9V battery

Against

• Metal only — no cables, timber or plastic
• Non-magnetic depth is half the headline figure

Typically £40–£55

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07

Proster 200EP tone generator and probe kit

Best cheap tracer — for the question “which cable is this?” rather than “is there a cable?”

Not a wall scanner, and worth including precisely because of that. A tone-and-probe kit clips a signal generator onto a cable you can reach — a dead circuit, phone line, alarm or network cable — and the inductive probe follows the tone along the run, through junction boxes and into the unlabelled tangle of a consumer unit cupboard. The 200EP pattern is a decades-old telecoms design sold under many names; Proster’s is the consistently well-reviewed one. The honest limits: it’s for identifying and roughly tracing accessible or de-energised cables, it isn’t depth-rated through masonry, and the generator must never be clipped onto a live conductor.

For

• Answers a question no wall scanner can — which cable is which
• Follows runs through walls and voids well enough to map a circuit
• Costs less than an hour of an electrician’s time

Against

• Not for live mains — identification tool, not a safety device
• Generic hardware; quality varies between badges

Typically £25–£35

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08

C.K T2272A non-contact voltage detector

The £12 sanity check — a voltstick for accessories, not a wall scanner

Every toolbag should end up with one of these in a pocket, so it may as well be a decent one. C.K’s T2272A is a non-contact voltage stick — hold it near a socket, switch, pendant or exposed cable and it lights and beeps in the presence of 70–1000V AC. The limits could not be more important: it senses through an accessory faceplate or cable sheath at close range, not through 20mm of plaster, so it is a check on things you can reach, never a wall scanner. Used properly — proving a faceplate is dead after isolation, before the tested-and-locked-off routine a professional would insist on — it’s the cheapest risk reduction on this page.

For

• Instant live/dead indication at accessories, visual and audible
• Reputable UK tool brand, not an anonymous pen
• Costs about as much as a decent sandwich round

Against

• Proximity only — useless through walls, and can miss well-shielded cable
• No substitute for proper proving dead with a two-pole tester

Typically £10–£15

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The outdoor half: CAT and genny

None of the tools above belongs anywhere near a trench. Outside, before anyone digs — fence posts, soakaways, the trench for an air-source heat pump’s power supply — the relevant instrument is a cable avoidance tool: the CAT, usually paired with a signal generator (the genny) that puts a traceable tone onto a service. This is the kit the HSE’s guidance on avoiding underground services (HSG47) is written around, and it finds live power cables, reradiated radio signals along metal pipes, and anything the genny is energising. What it does not find, unaided, is plastic — and most modern water and gas services are plastic, which is why utility plans and careful hand-digging of trial holes remain part of the method no matter what’s in your hand.

The pricing is trade pricing for trade risk: a C.Scope CXL4 runs to several hundred pounds, and a Radiodetection C.A.T4 with its genny is comfortably four figures — sold through specialist dealers rather than Amazon, often with calibration and training attached, because a CAT used by someone untrained is worse than no CAT at all. For the occasional domestic job the sensible route is hire: national tool-hire chains will do a calibrated CAT-and-genny for roughly £25–£40 a day. If a contractor proposes digging near your supply and has neither plans nor a CAT, that tells you something about the rest of their method.

What actually matters — and what doesn’t

The detector is the second line of defence, not the first. The first is dull procedure: look at where the sockets, switches and boilers are and assume cables and pipes run vertically and horizontally from them (the BS 7671 safe zones); turn the circuit off at the consumer unit where you can; prove it dead at the accessory. The detector then checks for the wiring that ignored the rules — which, in my experience of British housing, is a category with plenty of members.

Scan like you mean it. Every detector rewards the same technique: calibrate on a known-empty bit of the same wall, sweep slowly in overlapping passes both horizontally and vertically, mark every hit, and re-scan to confirm it repeats. When scanning for live cables, put load on the circuits first — lights on, kettle on — because an AC sensor hears current far better than idle voltage.

Depth figures are laboratory fiction. Every stated depth on this page was measured in ideal material. Damp plaster, dense block and reinforced render can halve them. Treat the spec as a ranking between tools, not a promise about your wall — and treat foil-backed plasterboard, common in mid-century cold-wall upgrades, as unscannable by anything here.

What the marketing pushes that you can skip. Phone apps, colour screens on £30 detectors, and “9-in-1” mode counts. An anonymous multi-scanner with nine modes has one sensor and nine ways of displaying it. Spend the money on the sensing technology — radar if plastic pipes matter, a proper inductive sensor if metal does — and on a brand whose depth claims have been publicly kicked at by ten thousand reviewers.

Questions I get asked

Do cable detectors actually work through UK walls? Within their physics, yes. On plasterboard over timber or metal frame they’re dependable. On solid masonry the picture is messier: dense block, damp lime plaster and salts all attenuate or mimic signals, which is why depth claims shrink and false positives grow on exactly the walls where older wiring is most anarchic. A radar scanner copes far better than a capacitive one, but on a difficult wall the professional habit stands — use the detector to find hazards, never to certify their absence, and keep fixings inside the drilling-safe logic of safe zones plus isolated circuits.

Where are cables supposed to run in a wall? BS 7671 puts concealed cables in prescribed zones: vertically or horizontally in line with any accessory (socket, switch, spur), and within 150mm of the ceiling line or an internal corner — otherwise they need earthed mechanical protection or burial deeper than 50mm, with RCD protection expected in modern installations. That’s where cables should be. Houses wired before the rules, altered since, or done badly obey nothing, which is why the zones tell you where to be most careful rather than where you may relax.

Will a cable detector find plastic water pipes? Only the radar type. Capacitive and inductive detectors — everything under about £100 — sense metal and energised conductors, and a plastic pipe is neither. A radar scanner like the D-tect family reads the density contrast, and a water-filled pipe shows more strongly than an empty one. The workaround with cheaper kit is indirect: find the copper tails and the metal clips, follow the line, and remember that a pipe run rarely does anything a plumber would have found inconvenient.

Do I need a CAT scanner for digging in the garden? For a vegetable bed, no. For anything deeper near the house or along the likely line of services — fence posts by the boundary where the supply comes in, a soakaway, footings for a garden room — the answer HSG47 would give is: get the utility plans (free via LSBUD for most networks), scan with a CAT-and-genny, and hand-dig trial holes near anything indicated. Hiring a calibrated CAT for £30-odd a day is cheap; striking an 11kV cable or a gas service is the other kind of expensive.

If the reason you’re drilling is a retrofit — cavity checks before insulation, or working out what a wall is actually made of — that’s the day job: the practice does PAS 2035 retrofit assessments where the investigation happens before the work, not after the claim — get in touch. The drill for the inspection hole has its own guide, the borescope that goes into it another, and there are more field-kit guides for the rest of the bag.

Small print. This guide is general information, not advice about your wall or your wiring; no detector reading proves a wall safe to drill, and work on electrical installations should be done by a competent person with circuits isolated and proven dead. Prices are indicative, move constantly and were checked at the time of writing; the linked page always shows the current price. As an Amazon Associate I earn from qualifying purchases.