A pipe wrench has serrated jaws set at an angle, so it bites harder the more you pull — that is the tool for round pipe. A monkey wrench has smooth, flat jaws square to the handle, made for nuts and square stock. On modern jobs its job is done by an adjustable wrench. They are not substitutes.
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People use the two names as if they meant the same tool, and hardware listings do not help. They describe two different machines with two different jobs, and picking the wrong one is how a chrome trap arm ends up scarred or a black iron nipple refuses to move.
What Is a Pipe Wrench?
A pipe wrench has two hardened, toothed jaws. The hook jaw floats slightly on the frame and sits at an angle to the heel jaw, so load pulls the jaws together and the teeth dig in. The harder you pull, the tighter it grips. That self-tightening action is the entire design.
RIDGID’s listing for the 14 inch model 814 describes full-floating forged alloy steel hook jaws for gripping power with quick ratcheting action during pipe adjustment, a pipe capacity of 2 inches, self-cleaning threads, and replaceable hook jaws, heel jaws and spring assemblies. The aluminum version weighs about 2-1/2 pounds, roughly 40 percent lighter than the heavy-duty pattern.
Those replaceable parts matter more than they sound. A pipe wrench is a consumable at the jaws: the teeth round over, the nut wears, and a worn wrench slips. On a tool with replacement jaws you rebuild it; on one without, you buy another.
What Is a Monkey Wrench?
A monkey wrench is an adjustable wrench whose smooth, flat jaws sit at 90 degrees to the handle, adjusted by a screw in the shank. It was the general-purpose fastener wrench of the era before standardized sockets, and it turns nuts, bolt heads and square stock. It does not grip round pipe, because flat parallel jaws have nothing to bite.
The name causes most of the confusion. In plenty of American workshops “monkey wrench” is used loosely for any big adjustable wrench, and sometimes for a pipe wrench. The jaw geometry, not the nickname, is what tells you what a tool can do.
Monkey Wrench vs Pipe Wrench: Which One Turns Pipe?
The pipe wrench, every time. Round stock offers no flats, so the only way to transmit torque is to bite into it, and that is what an angled, toothed jaw does. A smooth parallel jaw on round pipe will spin, polish a shiny band onto the pipe, and leave the joint exactly as tight as it was.
The reverse is also true and is the more expensive mistake. Put a pipe wrench on a hex nut, a supply-stop body or a chrome escutcheon and the teeth mark it permanently. Hex fasteners want flat jaws that load the flats.
Jaw Shape Is the Whole Difference
| Pipe wrench | Monkey wrench / adjustable | |
|---|---|---|
| Jaw face | Hardened teeth | Smooth and flat |
| Jaw angle | Angled, hook jaw floats | Square to the handle, parallel |
| Grip behavior | Tightens under load | Fixed by the screw setting |
| Made for | Round pipe and fittings | Nuts, bolt heads, square stock |
| Marks the work? | Yes, by design | Not if sized correctly |
Everything else — handle material, length, brand — is a preference. The jaw is the tool.
What a Monkey Wrench Is Called Today
Nobody stocks a true monkey wrench on a modern van. Its work passed to the adjustable wrench, which keeps the smooth parallel jaws and moves the screw to the jaw itself. Crescent’s listing for the 12 inch AC212VS calls it the original adjustable wrench, with a hex jaw design that reduces slippage by gripping fasteners tightly, a laser-etched scale in SAE and metric, and a jaw capacity of 1-1/2 inches or 39 mm.
A 12 inch adjustable covers most supply nuts, compression nuts, tub spouts and trap nuts a house will present. It is the tool people reach for when they say monkey wrench, and it is the one to buy.
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What Each One Will Ruin
Pipe wrench teeth leave permanent gouges, so keep them off anything you will see afterwards: chrome, brass, polished stops, escutcheons and finished trap arms. Our note on whether channel locks scratch chrome applies here with more force, since a pipe wrench bites harder than pliers.
Plastic is stricter again. Charlotte Pipe’s technical manual tells installers never to tighten threaded plastic fittings using common wrenches or tools designed for metallic piping systems, to use a strap wrench only, and to stop at two turns past finger tight. A pipe wrench on a PVC male adapter is how you split one.
Sizes and Capacity
Pipe wrenches are named by overall length, and the length sets the pipe capacity, not the reach. A 14 inch wrench such as the RIDGID 814 handles up to 2 inch pipe, which covers nearly all residential work; 18 inch is for bigger drain and gas lines. Two 14s beat one 18 and one 10, because most pipe work needs a back-up wrench on the other side of the fitting.
Adjustable wrenches are also named by length, but what matters is jaw capacity: the 12 inch Crescent opens to 1-1/2 inches. Buy the smallest one that opens far enough, because a long handle on a soft brass nut is a good way to round it.
When Neither One Is the Right Tool
For polished or plated pipe that has to stay unmarked, a strap wrench is the answer — the RIDGID 31335 strap wrench uses a polyurethane-coated woven nylon strap, which its listing describes as best for any polished pipe. For faucet nuts up inside a cabinet, the tool is a basin wrench, not either of these.
One rule covers both tools and it is a legal one on a job site: OSHA’s construction hand-tool standard states that wrenches, including adjustable, pipe, end and socket wrenches, shall not be used when the jaws are sprung to the point that slippage occurs. A sprung jaw is not a worn tool you nurse along; it is a tool that is finished.
Which Should You Buy?
If you own neither, buy both, and buy the pipe wrench first if there is threaded steel or a water heater in your future (cutting new threads on that steel is a job for a threading machine, not a wrench). A RIDGID 814 aluminum 14 inch pipe wrench is the size that covers residential pipe, and the Crescent 12 inch adjustable wrench is the modern monkey wrench for nuts and fittings. Together they handle most of what a house throws at you. More options in our guide to the best pipe wrenches and to channel locks and adjustable wrenches.
FAQ
Is a monkey wrench the same as a pipe wrench?
No. A monkey wrench has smooth flat jaws square to the handle and turns nuts and square stock. A pipe wrench has angled toothed jaws that tighten under load and turn round pipe. The names get swapped in conversation, but the jaws do different jobs and are not interchangeable.
Can I use an adjustable wrench on pipe?
Only on the flats. An adjustable wrench works on a hex union nut, a compression nut or a squared fitting; on round pipe it slips and polishes a band onto the surface without moving the joint. If the part you need to turn is round, the tool is a pipe wrench or a strap wrench.
What size pipe wrench do I need for a house?
A 14 inch. RIDGID lists a 2 inch pipe capacity for its 14 inch model 814, which covers residential supply, gas and drain sizes. Buy two rather than one, since most threaded joints need a back-up wrench holding the fitting while the other turns.
Why does my pipe wrench keep slipping?
Usually worn or packed teeth, or a sprung jaw. Better pipe wrenches take replacement hook jaws, heel jaws and spring assemblies, so a worn wrench can often be rebuilt instead of replaced. OSHA’s hand-tool rule is explicit that a wrench whose jaws are sprung to the point of slippage should not be used.
Can I use a pipe wrench on PVC?
Not on a threaded plastic joint. Charlotte Pipe tells installers never to tighten threaded plastic fittings with tools designed for metallic piping, to use a strap wrench only, and to stop two turns past finger tight. A toothed wrench both marks and stresses the fitting.
Bottom Line
Teeth and angle mean pipe; smooth and square means fasteners. A pipe wrench grips harder the harder you pull and marks whatever it touches, so it belongs on steel and on pipe that will be hidden. A monkey wrench, in its living form as the adjustable wrench, turns nuts without marking them. Owning one of each is the answer, not choosing between them.
Sources
- OSHA 29 CFR 1926.301 — Hand tools, paragraph (b): “Wrenches, including adjustable, pipe, end, and socket wrenches shall not be used when jaws are sprung to the point that slippage occurs.” Read September 2026.
- Charlotte Pipe Plastics Technical Manual — threaded connection do’s and don’ts, p. 33 (strap wrench only; never tighten with tools designed for metallic piping; two turns past finger tight). Read September 2026.
- Product specifications quoted above are read from each item’s current Amazon listing, September 2026.