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Quick answer from a licensed plumber: Buy the RIDGID SeekTech SR-20 with the ST-305 transmitter if you need one kit that finds sewer camera sondes and traces buried metal lines. If you mostly locate camera heads and drain cable tips, the RIDGID NaviTrack Scout with a 512 Hz 16728 sonde is the simpler buy. Pick the SR-24LE if you need GPS and Bluetooth records. Any locator gives an estimate: call 811 and expose the line before you dig.
Our pick for most plumbers: the RIDGID SeekTech SR-20 locator with the ST-305 line transmitter, for sonde locating and line tracing. Check the SR-20 + ST-305 kit on Amazon
A pipe locator is a receiver that finds a buried pipe by its signal. Plumbers use one two ways: to find the sonde on a sewer camera or drain cable, and to trace a metal water, gas or sewer line after a transmitter puts a signal on it. This guide compares RIDGID’s SR-20, Scout and SR-24LE receivers and its ST-305 and ST-510 transmitters, using RIDGID’s operator’s manuals and brochures. If you are shopping for a camera that already pairs with a locator, see our sewer camera with locator guide. The plumber behind this site uses RIDGID and Milwaukee tools on jobs. The specs below come from the maker documents, not from testing these models.
Pipe Locators Compared
| Locator | Type | Sonde | Line tracing | Power and weight | Maker |
|---|---|---|---|---|---|
| RIDGID SR-20 + ST-305 | Receiver + 5 W transmitter | 512 Hz default | Active, passive; 10 Hz–35 kHz | 4 C cells; 3 lb (receiver, no batteries) | RIDGID |
| RIDGID Scout + 16728 sonde | Receiver + 512 Hz sonde | 512, 640, 874 Hz, 33 kHz | Active 128 Hz, 8 kHz, 33 kHz; passive 50/60 Hz | 4 C cells; 3 lb with batteries | RIDGID |
| RIDGID SR-24LE (76813) | Receiver with GPS and Bluetooth | 512 Hz default | Same as SR-20 | 4 C cells or 18 V adapter; 3.8 lb (no battery) | RIDGID |
| RIDGID ST-305 (21898) | Line transmitter | None | Sends 1, 8, 33, 262 kHz; up to 5 W | 6 C cells; 2.5 lb with batteries | RIDGID |
| Milwaukee 2580-21 (not linked) | Receiver kit | Yes, per Milwaukee | Sewer line tracing, per Milwaukee | M12 battery | Milwaukee |
Specs from RIDGID’s SR-24LE / SR-20, Scout, ST-305 and ST-510 operator’s manuals and RIDGID’s 2023 European locator brochure, read on October 1, 2026. RIDGID’s older SR-24 / SR-20 manual lists the SR-20 at 3.3 lb without batteries; the table uses the current manual.
Sonde Locating vs Line Tracing
Sonde locating
A sonde is a small transmitter you push into the pipe. It sits behind a sewer camera head, on the end of a drain cable or on a jetter hose. RIDGID’s Scout manual says a sonde gives off a dipole field, shaped like the field of a bar magnet, with two poles and an equator. You set the receiver to sonde mode at the sonde’s frequency, usually 512 Hz, sweep the mast toward the strongest signal, then walk in and pinpoint the peak. This works on any pipe the sonde fits through, plastic or clay included. RIDGID notes sondes have trouble signaling through cast and ductile iron.
Active line tracing
Line tracing follows the pipe itself. A transmitter puts a signal on a metal pipe or tracer wire, and the receiver follows the cylindrical field along the line. RIDGID’s ST-305 manual lists three ways to do that: clip the leads to the pipe and a ground stake (direct connect), close an inductive clamp around it, or set the transmitter on the ground over the line and let its internal coil induce a signal. RIDGID’s Scout manual says to use a direct connection whenever possible, because induction gives the line a weak signal.
Passive line tracing
Passive mode uses signals already on a line, such as 50 or 60 Hz from power lines or radio energy picked up by long conductors. RIDGID’s SR-24LE / SR-20 manual says measured depth may not be accurate in passive mode and to confirm with an active trace when you can. Passive mode is a sweep for what is there, not a way to find your sewer lateral (our judgment).
Before You Buy
- Match the frequencies. Your receiver must read your camera sonde (usually 512 Hz) and your transmitter’s trace frequency. RIDGID’s manuals warn that using a sonde frequency in line trace mode, or the reverse, gives wrong depth readings.
- Decide if you need a transmitter. If you only find camera heads, a receiver and the camera’s built-in sonde may be enough. To trace a water service or gas line, you need a transmitter like the ST-305.
- Know what you are tracing. A transmitter signal needs a metal path. RIDGID says plastic water and gas installs typically have a trace wire; clip to that. Plastic sewer pipe with no wire needs a sonde.
- Plan for power. The SR-20 and Scout take four C cells, the ST-305 takes six and the ST-510 takes eight D cells. RIDGID sells an 18 V adapter for its receivers; it comes with the SR-24LE.
- Budget for safety, not just the tool. RIDGID warns never to connect a transmitter to a line known to carry dangerous current, and to attach the ground lead first. RIDGID’s manuals say to follow local One Call procedures; plumber’s note: in the US, that means calling 811 before you dig.
RIDGID SeekTech SR-20 Locator + ST-305 Transmitter (21893 + 21898)
Receiver plus 5 W line transmitter · line trace and sonde modes · 512 Hz default sonde frequency · traces any frequency from 10 Hz to 35 kHz, per RIDGID · omnidirectional mapping display · four C batteries · 3 lb without batteries, per the current manual
The SR-20 is the receiver to buy if you locate both camera sondes and buried lines. RIDGID’s manual covers two modes: Line Trace Mode, for tracing a pipe or cable you have put a signal on, and Sonde Mode, for finding a transmitter inside a pipe. RIDGID’s SR-24LE / SR-20 manual lists 512 Hz as the default sonde frequency and user-programmable frequencies from 10 Hz to 35 kHz; RIDGID’s European brochure adds that up to 30 can be set. The display shows a tracing line, guidance arrows, a proximity number, signal strength and a continuous depth reading. RIDGID says the receiver watches for distortion and warns you when the field looks wrong.
This bundle adds the ST-305 transmitter, so you can trace metal pipe, not just find a sonde. RIDGID’s ST-305 manual lists three hookups: direct connect to the pipe and a ground stake, an optional inductive clamp, or inductive mode with no hookup at all. It runs up to 5 W on six C cells. RIDGID’s manual for the newer SR-24LE also covers the SR-20 and says the two are functionally identical except that the SR-20 has no GPS or Bluetooth. If your main job is finding a camera head, Amazon also lists the SR-20 bundled with RIDGID’s 16728 512 Hz battery sonde.
- Sonde and line trace modes in one receiver
- Traces 10 Hz to 35 kHz, per RIDGID
- Distortion warning on screen, per RIDGID
- Bundle includes a 5 W line transmitter
- No GPS or Bluetooth (that is the SR-24LE)
- Runs on four C cells; 18 V adapter sold separately, per RIDGID
- More receiver than a homeowner needs (our judgment)
Verdict: The pick for a plumbing or drain company that needs to find camera heads and trace water, gas or sewer lines with one kit.
RIDGID NaviTrack Scout Locator + 16728 Battery Sonde (19238 + 16728)
Sonde and line locator · sonde frequencies 512, 640, 874 Hz and 33 kHz · active trace 128 Hz, 8 kHz, 33 kHz · passive 50 and 60 Hz · 3 lb with batteries · four C batteries · 16728 sonde: battery-powered, 512 Hz
The Scout is RIDGID’s simpler receiver, built around finding sondes. RIDGID’s Scout manual lists sonde frequencies of 512, 640 and 874 Hz and 33 kHz, active line trace at 128 Hz, 8 kHz and 33 kHz, and passive 50 and 60 Hz. It weighs 3 lb with batteries and runs on four C cells. The manual explains that a sonde puts out a dipole field with two poles and an equator. The Scout shows the poles on its map, and the sonde sits at the point of strongest signal, between them.
This bundle pairs it with RIDGID’s 16728 battery sonde. RIDGID’s European locator brochure says the sonde attaches to a drain cleaning cable or a water jet hose, sends a 512 Hz signal and flashes an LED while it transmits. The Amazon listing for the 16728 sonde sold alone says it runs up to 4 hours on one AAA cell, with a typical range of 25 feet in air and 15 feet in cast iron with a NaviTrack receiver. That lets you find a stoppage at the end of a drain cable. The Scout also finds the sonde in a SeeSnake camera: RIDGID’s CS10 manual says many SeeSnake systems have a built-in 512 Hz sonde that a Scout set to 512 Hz can detect. For line tracing instead, Amazon lists the Scout bundled with the ST-305 transmitter.
- Finds 512 Hz camera and cable sondes, per RIDGID
- Map shows poles and equator to pinpoint a sonde
- 3 lb with batteries, per RIDGID
- Bundle adds a sonde for drain cables and jetter hoses
- Fewer preset trace frequencies than the SR-20 in RIDGID’s Scout manual (the Amazon listing adds 1 kHz)
- No 10 Hz to 35 kHz programmable range listed
- Sondes struggle through cast and ductile iron, per RIDGID
Verdict: The pick if you mostly locate sewer camera heads and drain cable tips, and only sometimes trace a line.
RIDGID SeekTech SR-24LE Line Locator with Bluetooth and GPS (76813)
SR-20 functions plus built-in GPS and Bluetooth LE · data to SD card or a phone via the RIDGIDtrax app · 18 V Li-Ion battery adapter included, per RIDGID · IPX4 · 3.8 lb without battery or adapter
The SR-24LE is the SR-20 with location records added. RIDGID’s manual says the SR-24LE has integrated GPS and Bluetooth Low Energy and is otherwise functionally identical to the SR-20. RIDGID’s European brochure says the Data Output feature saves locate data to an SD card, sends it to a Bluetooth device, or both, and that the RIDGIDtrax app maps tracks and waypoints and exports them to GIS software. The manual lists 1 m (3.3 ft) GPS accuracy, and adds a note that the GPS maker states 4.6 cm. Trees and buildings affect it, per RIDGID.
RIDGID includes a battery adapter that takes RIDGID or Makita Li-Ion packs, according to the manual; the battery is not included. It weighs 3.8 lb without battery or adapter, against 3 lb for the SR-20 (both per the current manual). Plumber’s note: for most service plumbers, the depth and position you spray on the ground is the record. The GPS earns its keep for contractors who document sewer laterals or bid utility work (our judgment). On October 1 the Amazon listing was sold by Amazon.com with only 2 left and more on the way, so check stock.
- Built-in GPS and Bluetooth LE, per RIDGID
- Saves locate data to SD card or a phone app
- 18 V battery adapter included, per RIDGID
- Same locating features as the SR-20, per RIDGID
- Low Amazon stock on October 1
- Heavier than the SR-20 (3.8 lb vs 3 lb)
- No transmitter in the box
Verdict: Buy it if you need to log and share where lines run, not just mark them for the dig.
RIDGID SeekTech ST-305 Line Transmitter (21898)
5 W nominal · 1, 8, 33 and 262 kHz · two frequencies at once in direct connect · direct connect, inductive clamp (optional) or inductive mode · six C cells · 2.5 lb with batteries · high voltage LED above 62 VAC
If you already own a receiver, the transmitter is what lets it trace a buried metal line. RIDGID’s ST-305 manual says it puts an active signal on a pipe or cable so a receiver such as the SR-20 can trace it. Its frequencies are 1, 8, 33 and 262 kHz, and in direct connect it can send two at once. Power runs from 25 mA up to 5 W. It weighs 2.5 lb with its six C cells. A red LED flashes if it sees more than 62 VAC on the line.
For larger jobs RIDGID makes the ST-510 (21903). It is not linked: on October 1, 2026, its Amazon listing showed 3 left from a third-party seller, which fails our seller and stock rules. Its manual lists 10 W nominal, five current settings from 4 to 600 mA, a 48 ft extended coil cord, eight D cells and 7.5 lb with batteries. Plumber’s note: check that the transmitter and receiver share a frequency. The ST-305 lists 8 and 33 kHz, and the Scout traces at 8 and 33 kHz, so those two pair. The SR-20’s default active frequencies include 1, 8 and 33 kHz (our cross-check of RIDGID’s manuals and brochure).
- Three hookup methods, per RIDGID
- Sends two frequencies at once in direct connect
- 2.5 lb with batteries, per RIDGID
- High voltage warning LED
- Traces metal lines only; plastic pipe needs a trace wire
- Inductive clamp sold separately
- 5 W; the ST-510 goes to 10 W
Verdict: The add-on for anyone with a Scout or SR-20 who needs to trace water service, gas or metal sewer pipe.
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What About Milwaukee?
Milwaukee makes the 2580-21 M12 Pipeline Locator Kit. Milwaukee’s product page says it pinpoints sewer camera sondes and traces underground sewer lines, shows a directional arrow toward the sonde at startup, uses two 3D antennas, has a 4.3 in. color screen and an IP65 rating, and runs on M12 REDLITHIUM batteries. We did not link it. On October 1 the only Amazon listing we found was a third-party listing whose title began “Fits Milwaukee,” shipping in 6 to 7 days, not a Milwaukee-sold item. We also did not find a Milwaukee operator’s manual with full specs. If you run a Milwaukee camera, buy the locator from an authorized Milwaukee dealer. See our Milwaukee vs RIDGID sewer camera comparison for the cameras.
What About Other Pipe Locator Brands?
Amazon sells other 512 Hz receivers and sondes under brands like VEVOR and many unbranded sellers. We did not find operator’s manuals for them with the depth checks, frequency lists and safety rules RIDGID publishes, and the ones we checked were sold by third-party sellers. We do not rank them. If you buy one, make sure it reads your camera’s sonde frequency, and test it on a sonde you can see before you trust it underground.
How to Use a Pipe Locator: Notes From the Manuals
Finding a sonde. RIDGID’s Scout manual says to check the sonde works with the receiver before it goes into the line. If you do not know which way the pipe runs, push the sonde about 15 feet in to start. Sweep the mast toward the strongest signal, lower it to vertical and walk in until the signal peaks, then move the receiver in all directions to confirm it drops off. If the sonde is tilted, the poles shift; RIDGID says the point of maximum signal is still where the sonde is. A sonde that fell into a break or a vertical drop can still be found this way.
Tracing a line. Set the transmitter and receiver to the same active trace frequency, per RIDGID’s SR-24LE / SR-20 manual. Check the signal about 3 ft from the transmitter lead first. A good circuit reads strong and steady. Then balance the guidance arrows and follow the tracing line. With induction, keep your distance: RIDGID warns that if the receiver is too close, it picks up the transmitter through the air, not the pipe. Its 45 degree tilt test checks for this.
Checking the depth. Touch the lower antenna to the ground over the target and note the depth. Raise the receiver about 6 in. The reading should go up by about 6 in. RIDGID says an unchanging or wildly changing reading points to a distorted field or a weak signal. Plumber’s note: before you dig on a sonde locate, run the sewer camera back to the problem and confirm the footage counter agrees with your mark. If a drain cleaning machine cable is stuck, put the sonde on the cable and locate the tip.
Distortion. RIDGID’s Scout manual says locating is not an exact science and that no maker says to follow the instrument alone. Expect trouble near other utilities, at tees and splits, and when you induce the signal rather than connect directly. Try a lower frequency and move the ground stake away from the line, per RIDGID.
FAQ
What is the best pipe locator for plumbers?
For most plumbers, the RIDGID SeekTech SR-20 with an ST-305 transmitter. The SR-20 finds 512 Hz camera sondes and traces lines, and the ST-305 puts the signal on a metal pipe. If you mostly find sewer camera heads, the lighter RIDGID NaviTrack Scout with a 16728 sonde covers that job.
Can a pipe locator find plastic pipe?
Not by itself. A receiver senses electromagnetic fields, not the pipe, per RIDGID’s Scout manual. For plastic sewer pipe, push a sonde or a sewer camera with a sonde through it and follow the sonde. For plastic water or gas pipe, RIDGID’s ST-305 manual says installs typically have a trace wire, and you clip the transmitter to that wire.
What frequency is a sewer camera sonde?
Usually 512 Hz. RIDGID’s CS10 manual says many SeeSnake systems have a built-in sonde that sends a 512 Hz signal, and RIDGID lists 512 Hz as the default sonde frequency on the SR-20 and SR-24LE. Set the receiver to the same frequency and to sonde mode, not line trace mode.
How accurate is the depth on a pipe locator?
Treat it as an estimate. RIDGID’s SR-24LE / SR-20 manual says to use measured depths as estimates only, and lists distortion, nearby utilities, tees, soil and other conditions as factors. It gives a depth check: lift the receiver about 6 in. and the reading should rise by about the same amount. RIDGID says passive depth may not be accurate at all.
Do I still need to call 811 if I have a locator?
Yes. RIDGID’s manuals say several utilities may share the same area, to follow local guidelines and One Call procedures, and that exposing the utility is the only way to be certain of its location. A locator helps you find your own pipe. It does not clear a dig.
Why Trust Plumbing Picks
Plumbing Picks is written by a licensed Georgia journeyman plumber who uses RIDGID and Milwaukee tools on jobs. Every spec here comes from the RIDGID and Milwaukee documents linked below, or from the Amazon listings we link; we did not test these models ourselves. On October 1, 2026, every linked listing was in stock and sold by Amazon.com. The SR-24LE showed low stock with more on the way. If you buy through a link we may earn a commission at no extra cost to you. Nobody pays to be included here. More on who writes this and how we pick.
Sources
- RIDGID: SeekTech SR-24 / SR-20 Operator’s Manual, SR-24LE / SR-20 Operator’s Manual (RIDGID SeekTech manual site)
- RIDGID Europe: SeekTech SR-20 / SR-24 LE line locators and transmitters brochure (2023)
- RIDGID: Scout Sonde and Line Locator Operator’s Manual, NaviTrack Scout Operating Instructions (Ridge Tool Europe)
- RIDGID: SeekTech ST-305 Operator’s Manual
- RIDGID: SeekTech ST-510 Operator’s Manual
- RIDGID: SeeSnake CS10 Operator’s Manual (locating the camera sonde)
- Milwaukee: 2580-21 M12 Pipeline Locator Kit (product page)
- Amazon listings for the RIDGID SR-20 bundles, NaviTrack Scout bundles, SR-24LE (76813), ST-305 (21898) and 16728 sonde, linked above
Bottom Line
The RIDGID SR-20 with an ST-305 transmitter is the pipe locator to buy for most plumbers: it finds 512 Hz camera sondes and traces metal lines and tracer wire. The NaviTrack Scout with a 16728 sonde suits drain and camera work, the SR-24LE adds GPS and Bluetooth records, and the ST-305 turns a receiver you already own into a line tracer. Match the frequencies, check the depth reading, and call 811 before you dig.