For plumbing, get the RIDGID 31400 12-inch adjustable spud wrench; RIDGID lists a 3/8 to 2-5/8-inch capacity, enough for flush valve, spud and strainer nuts. Add the Superior Tool 3845 SinkDrain wrench for trap and strainer nuts under sinks. An ironworker’s spud wrench is a different tool.
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This guide covers the plumber’s spud wrench and the drain nut wrenches that work alongside it.
Plumber’s spud wrenches compared
| Wrench | Fits (maker) | Choose it when |
|---|---|---|
| RIDGID 31400 spud wrench | Adjustable, 3/8 to 2-5/8 in. capacity, 12 in. | Large flat nuts: flush valve and urinal spuds, strainers |
| Superior Tool 3845 SinkDrain | 1-1/4 and 1-1/2 in. trap nuts, strainer nuts, stepped brass nut sizes | Under-sink drain nuts and basket strainers |
Search for “spud wrench” and you will find two different tools. Ironworkers use a spud wrench with a pointed handle to line up bolt holes in steel. Plumbers use a spud wrench to turn the large, thin nuts on toilet tank flush valves, urinal and toilet spuds, sink strainers and trap connections. This guide covers the plumbing tool.
RIDGID 31400: the classic plumber’s spud wrench
Choose the RIDGID 31400 for big, flat plumbing nuts. RIDGID lists (ridgid.com) a 12-inch adjustable spud wrench with narrow jaws for tight places, a pipe capacity of 3/8 to 2-5/8 inches, a weight of 2-1/2 pounds and a full lifetime warranty.
Its listed capacity covers large plumbing nuts such as flush valve lock nuts and sink strainer nuts, and RIDGID describes its narrow jaws as made to fit into tight places. The jaws are smooth and meant for the flats of a nut, not for gripping round pipe.
On October 15, 2026, the standard new offer sold by Amazon.com showed stock with part 31400.
Check RIDGID 31400 12-inch spud wrench on Amazon →
Superior Tool 3845 SinkDrain: for drain nuts
Choose the Superior Tool 3845 for sink drain nuts. Superior Tool lists (superiortool.com) it for 1-1/2-inch kitchen and 1-1/4-inch bathroom P-trap nuts, kitchen sink basket strainer nuts and 1-1/4 to 1-1/2-inch plastic DWV nuts with wing tabs, with a stepped head that fits 1-1/4, 1-13/16, 2 and 2-1/16-inch brass drain nuts, a 3/8-inch square drive recess and nickel-plated steel construction, made in the USA.
It is lighter and more specific than an adjustable spud wrench, and the square drive lets you add a ratchet when a strainer nut is tight.
On October 15, 2026, the standard new offer from a third-party seller showed stock with part 03845.
Check Superior Tool 3845 SinkDrain wrench on Amazon →
What plumbers use a spud wrench for
- Toilet flush valves: the large lock nut under the tank that holds the flush valve. Our flush valve guide notes Fluidmaster’s limit of no more than 1/2 turn past hand tight, so go easy.
- Tank-to-bowl and spud gaskets: when a two-piece toilet’s spud gasket is replaced; our tank-to-bowl gasket guide covers parts by brand.
- Commercial flush valves: the spud coupling on wall-hung toilets and urinals with flushometers; our Zurn flush valve guide covers repair kits.
- Sink strainers: the big lock nut under a kitchen basket strainer; see our basket strainer guide.
Holding the strainer while you turn the nut
A strainer spins in the sink when you turn its lock nut. Superior Tool’s basket strainer wrench (part 3890) (superiortool.com) is made to hold most basket strainers in place from above while the nut is tightened, with a 6-inch sliding T-handle and a 3-inch handle offset. We did not find a current new Amazon offer for it, but any helper holding the strainer with a pair of pliers handles through the crossbars does the same job.
Spud wrench, basin wrench or pipe wrench?
A spud wrench turns large flat nuts you can reach from the side. A basin wrench turns faucet nuts up behind a sink where nothing else fits; our basin wrench guide covers those. A pipe wrench grips round pipe with toothed jaws and will mar a finished nut; our pipe wrench guide covers them.
Where a spud wrench comes in on a toilet flush valve swap: shut off and drain the tank, disconnect the supply, remove the tank bolts and lift the tank off the bowl, then turn the large lock nut under the tank to free the old flush valve. Reverse the steps with the new valve and gasket, snugging the lock nut within the maker’s limit before setting the tank back on with a new tank-to-bowl gasket. The same wrench then fits the supply coupling nut if it is a large plastic one.
Plastic nuts are easy to crack. Snug them by hand first and use the wrench only to finish, especially on plastic flush valve nuts and slip nuts.
Using a spud wrench without damage
Set the jaws snug on the flats before you turn; a loose jaw rounds the nut. Turn steadily rather than jerking, and support the fixture so the force does not crack china or twist a drain. On a toilet tank, keep the tank level and do not overtighten the nut or bolts, since vitreous china can crack under uneven pressure.
On a commercial flushometer, the spud coupling joins the flush valve outlet to the spud on the china. Shut the control stop first, and wrap the jaws with tape on a chrome coupling so the finish is not scratched. Hold the flush valve body steady while you turn, so the force does not twist the supply or crack the fixture.
For an old corroded brass nut, a little penetrating oil and patience beat a cheater bar. Our penetrating oil guide covers options.
If you are an ironworker
The construction spud wrenches you will see in search results, with a tapered handle for aligning holes, are a different tool and not covered here. They are built for structural bolts, not plumbing nuts.
Which to buy
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Before buying, look at the nuts you meet most often. Plastic flush valve and strainer nuts usually need only a snug turn, and a stepped drain wrench or even hand pressure may be enough. Old brass or chrome strainer nuts, commercial spud couplings and seized slip nuts are where a full-size adjustable spud wrench earns its place in the truck.
If you only buy one, the RIDGID 31400 covers the widest range of plumbing nuts thanks to its 3/8 to 2-5/8-inch capacity. Add the Superior Tool 3845 if you work under sinks often; it is faster on trap and strainer nuts and takes a ratchet.
Frequently asked questions
What is a spud wrench used for in plumbing?
Turning large, thin nuts: toilet flush valve lock nuts, toilet and urinal spud couplings, sink strainer nuts and trap nuts.
What size spud wrench do plumbers need?
An adjustable one covers the most. RIDGID lists a 3/8 to 2-5/8-inch capacity for its 12-inch 31400.
Is a plumber’s spud wrench the same as an ironworker’s spud wrench?
No. The ironworker tool has a pointed handle for aligning bolt holes; the plumber’s tool has thin, smooth, wide-opening jaws for flat nuts.
What wrench fits a kitchen sink strainer nut?
A spud wrench or a stepped drain wrench like the Superior Tool 3845, which Superior Tool lists for basket strainer nuts.
How tight should a toilet flush valve nut be?
Our flush valve guide cites Fluidmaster: no more than 1/2 turn past hand tight.
How we chose
This document-based guide makes no hands-on testing claim. We read RIDGID’s spud wrench page and Superior Tool’s SinkDrain and basket strainer wrench pages, and used the flush valve nut limit from our flush valve guide, which cites Fluidmaster. On October 15, 2026, both linked standard new offers showed stock. Read our selection method and about Plumbing Picks.
Primary sources
- RIDGID 31400 Spud Wrench (ridgid.com): 12 in., narrow jaws, 3/8–2-5/8 in. capacity, weight, warranty.
- Superior Tool 3845 SinkDrain Wrench (superiortool.com): fits trap, strainer and brass drain nuts; 3/8 in. drive.
- Superior Tool 3890 Basket Strainer Wrench (superiortool.com): holds strainers; 6 in. T-handle; 3 in. offset.