Plumbing — know where the shutoff is.

Shutoff to fixture is fair game. Anything inside the wall — slow down, or call. Five guides covering the projects that earn their place: faucets, supply lines, toilet rebuilds, P-traps, and the single most important skill — knowing where the main water shutoff is. We've ranked them by safety, then cost, then leverage. Plumbing is a 3 out of 5 on the DIY difficulty scale. The barrier is not complexity — it's knowing when you're crossing into pro territory. Master these five repairs, know your limits, and you'll save thousands in service calls while keeping your home safe from water damage.

Five plumbing projects, ranked by what they're worth

If you only ever tackle five plumbing projects as a homeowner, do these. Ranked by confidence gained, dollars saved, water damage prevented, and the likelihood you'll face them in the next five years.

1. Know where the main water shutoff is and test it

The single most important skill. 15 minutes now prevents panic later. Locate the main shutoff valve, trace the supply line, test the valve twice a year. If a pipe bursts at 2am, you'll already know exactly where to turn. This one skill prevents catastrophic water damage. You will use this knowledge in an emergency. Spend the 10 minutes now.

2. Replace a leaky faucet washer or cartridge

The drip that costs $5 in water and $200 in a service call. Shut off the stop valve under the sink, pull the cartridge, swap the seal. 30 minutes, ~$12. Most homes have at least one leaky faucet at any given time. This is the repair that makes you feel like a home-repair competent person — it's simple, visible, and immediate.

3. Clear a clogged drain with a plunger and snake

Before you call a drain cleaner, a $15 plunger and a $20 drain auger solve 80% of clogs. The technique matters more than the tool. A slow drain in a bathroom is not an emergency. It's a Saturday project. Plunge first (three solid plunges, then rest). If that doesn't work, snake. Most clogs are hair and soap — both succumb to a $20 auger in 20 minutes.

4. Replace a toilet flange or repair a running toilet

A running toilet costs $50/month in water. The fill valve is $18 and takes 20 minutes to swap. The flange takes an afternoon but is one of the last repairs you'll ever make on that toilet. Tackle the fill valve first — it's 99% likely to be the problem. If you hear water running 10 seconds after the flush completes, the fill valve is failing and needs swapping.

5. Repair a P-trap or replace a supply line

A slow leak under the sink is easy to find and fix. The P-trap is held on with two slip nuts and a wrench. Replace a supply line with braided stainless and you've bought yourself 25 years instead of 5. Supply lines are the one part of your plumbing that has an actual expiration date. Rubber hoses age. They crack. They fail. One afternoon replacing all four (sink hot/cold, toilet) prevents future emergency calls.

Every plumbing guide, in one list

Five guides total, organized by what breaks first and what's safe to fix yourself. Each guide walks you through the repair step-by-step, with the exact tools you'll need and where to buy them.

Faucet repairs

• How to fix a leaky faucet. Identify the drip point, shut off the stop valve under the sink, replace the cartridge or washer. The whole repair takes 30 minutes and costs ~$12 in parts. Single-handle or double-handle, compression or cartridge — the technique changes but the principle is the same: find the seal, replace it, reassemble.

Toilet repairs

• How to stop a running toilet. The fill valve is the culprit 95% of the time — it stops closing or the flapper seal fails. Swap it and save $50/month in water. 20 minutes, ~$18. This is one of the fastest wins in home repair. You'll hear the water shut off instead of running continuously.
• How to replace a toilet flange. The silent killer of toilets. When the flange rots or cracks, the wax ring fails and water leaks down into the subfloor. Full removal, replacement, re-seal. Half a day, ~$80. This is the one toilet repair that feels big but is simpler than it looks once you understand the sequence.

Drain repairs

• How to clear a clogged drain without a service call. Plunger first, then auger. Know the difference between a trap clog (under the sink, in the P-trap) and a line clog (deeper in the wall). 1 hour, ~$40. Most clogs happen in the trap and are solved in 10 minutes. The deep clogs need patience and a 25-foot auger.

Supply line replacement

• How to replace a supply line before it fails. Rubber hoses fail every 5–7 years. Braided stainless lasts 25+ years. Shut off, unscrew, replace. 20 minutes per line, ~$15 per line. This is one of the easiest preventive repairs — you're not fixing a leak, you're preventing one. Replace all four supply lines (hot and cold to sink and toilet) and you've bought yourself peace of mind for two decades.

When this is DIY

Surface repairs below the shutoff valve are almost always safe — faucet cartridges, toilet fill valves, P-trap seals, supply lines, drain clogs. The rule: if water stops when you close the shutoff valve under the fixture, you're OK to proceed. The repair happens in open air, not behind a wall, and if something leaks, you catch it immediately.

DIY green light

Go ahead if your repair is (a) downstream of a shutoff valve, (b) visible (not behind a wall), (c) uses simple hand tools (wrench, plunger, auger), and (d) doesn't require special certifications or permits. Examples: leaky faucet under the sink, running toilet, drain clog, supply line swap, P-trap seal. Shut off the water, make the repair, test it, turn water back on. If it leaks, you're six inches from your bucket and towels.

Why the shutoff valve is the boundary

Every plumbing repair above the shutoff valve or inside the wall is pro work. The difference is containment and liability. Mistakes under the sink affect only that cabinet and your pride. Mistakes in the wall affect the entire home's structural integrity. A solder joint that fails six months later is a water stain on the ceiling. A supply line that fails under the sink is a bucket and a phone call to your plumber (not an emergency — you've shut the water off).

When to call a pro

Anything in the wall stays in the wall. Water heater repairs, solder joints, main line clogs, slab leaks, anything that requires a permit, galvanized pipe replacement, and any repair that happens above the shutoff valve or requires you to cut into drywall — those are pro territory. The hourly cost of a plumber is cheaper than the permanent damage a mistake costs. If the job requires cutting drywall or soldering copper, hire it out. If the job is above your head and the shutoff valve, call a plumber.

Pro-only territory

• Main shutoff repairs. If the main shutoff leaks or won't close, a plumber fixes it. You can't shut off water to test a repair when the main itself is broken.
• Solder joints. Copper soldering needs a professional touch and the right flux/heat. DIY solderers often get weak joints that leak years later.
• Main line clogs. A main line clog is past the trap and requires power equipment. This is not a DIY auger situation.
• Anything that requires a permit. Your jurisdiction requires permits for gas line work, water heater replacement, and main supply work. Permits exist to catch dangerous DIY attempts. Respect them.
• Galvanized pipe replacement. Old galvanized supply lines corrode from the inside and must be replaced. This is frequently a whole-house job requiring new fittings throughout.
• Slab leaks. Water leaking under your foundation concrete is not DIY territory. This requires detection equipment and often excavation.
• Water heater work. Gas heaters require gas line experience. Electric heaters require understanding of the service panel. Mistakes here are dangerous and expensive.
• Anything behind a wall that you can't see. If you can't see the repair without opening drywall, and the job is to fix something inside that wall, call a pro. The cost of drywall patching will exceed the labor savings of DIY.

Common plumbing mistakes (and how to avoid them)

These are the repairs that start as simple jobs and turn into water damage. All of them are preventable if you know what to avoid.

1. Overtightening a slip nut and cracking the tailpiece

Slip nuts only need to be hand-tight plus a quarter turn. One extra turn of the wrench cracks the fitting. Then you've got a new tailpiece and a bigger mess. The fix: hand-tight only. If it leaks, go back a half turn and use plumber's putty or silicone around the joint first. This is why a tongue-and-groove plier matters more than raw torque — you're tightening by feel, not by force.

2. Shutting off the wrong valve and panicking

The stop valve under your sink controls that sink only. The main shutoff controls the whole house. If you shut off the sink valve and water still flows — don't panic, you just grabbed the wrong one. Know where both are before you need them at 2am. Label them. Trace the lines with your finger. Test both valves twice a year so you're not learning the difference during an emergency.

3. Using teflon tape on a slip-joint connection

Teflon tape is for threaded connections (the main shutoff, the angle stop). Slip joints (the P-trap, tailpieces) use a rubber washer and plumber's putty or silicone. Teflon on a slip joint means water weeping in 6 months and a second repair. The mental rule: if you're turning the connection by hand without a wrench, don't use tape. If you need a wrench, tape goes on the threads.

4. Mismatched washers in a faucet cartridge assembly

Every washer size matters — it's the seal between parts. A 7/8" washer where a 1/2" should go doesn't seal, and the cartridge fails immediately. Bring the old cartridge to the hardware store. Match exact. Better yet, keep the old cartridge as a sample so you don't have to go back twice.

5. Ignoring slow leaks and hoping they'll go away

A drip under the sink that you ignore for 6 months becomes a soft subfloor and mold. A slow leak behind a wall becomes a structural problem. Fix slow leaks fast. The 20-minute repair now costs $50. The repair ignored for a year costs $5,000. A water stain on the ceiling below a bathroom is a red flag — don't wait. A wet spot under the sink needs a towel and a bucket while you assess, then a repair plan within a week.

Bonus mistake: Not testing your fix before you put everything back together

Before you put the cabinet back under the sink, turn the water back on and let it run for 30 seconds with the drain plugged. Watch for drips. This catches 90% of slip-nut problems while you still have your wrench in hand. The cost of a second fix is steep in time and embarrassment.

The toolkit

Plumbing is a 3 out of 5 on the DIY-ability scale — accessible if you understand the rule (shutoff to fixture is fair game, in-wall is not). The barrier is not the tools; it's knowing what you're looking at. A basin wrench, an adjustable wrench, a plunger, and a drain auger solve 95% of the repairs you'll face. The rest is knowing when to call. Total investment to cover most repairs: under $200.

Essential tools (you'll use these monthly)

• Basin wrench ($25). The only wrench that fits in the tight space under a sink. Reaches up and around without removing the sink. It's the one tool that makes faucet repairs accessible. Worth every penny.
• Adjustable wrench, 10-inch ($18). For slip nuts, shut-off valves, and anything hexagonal under the sink. One wrench, a dozen uses. The 10-inch size is the right balance — big enough to grip firmly, small enough to fit in tight spaces.
• Plunger, cup-style ($12). For sink and tub drains. The flange plunger is for toilets only — different sealing pattern. A good plunger is your first defense against a drain call.
• Drain auger, 25-foot ($30). For clogs beyond the trap. The 50-foot ($45) is overkill unless you're snaking main lines. A 25-footer handles 90% of household clogs.
• Tongue-and-groove pliers, 10-inch ($22). Adjusts for any size, locks in place. Grabs frozen nuts better than an adjustable wrench. This is the pliers that turns a plumbing job from frustrating to manageable.

Sealants and consumables

• Plumber's putty ($6). For sealing around fixture drains. Teflon tape only for threads — never slip joints. One tub lasts years.
• Silicone caulk and caulking gun ($14 total). The modern alternative to putty. Cleaner, longer-lasting, repairable. For a professional finish, silicone is worth the learning curve.
• Teflon tape ($3). For all threaded connections (main shutoff, angle stops). One roll lasts through dozens of repairs.

Electrical and diagnostic

• Voltage tester ($12). Before you touch a disposal, test the outlet. Electricity + water = never. Non-contact testers are safer and faster than probes.
• Flashlight or headlamp ($15). Under-sink work is dark work. A headlamp beats a flashlight because your hands are full.

Containment

• Bucket and old towels ($8). More repairs fail for lack of a bucket to catch water than lack of tools. Keep three old towels under the sink at all times. When you open a P-trap, water comes out — be ready.
• Shop towels or rags ($5). Disposable is cheaper than ruining good towels. Keep a roll under the sink alongside the cloth.

Optional but smart

• Shutoff valve locator key ($20). Helps you find and turn the main shutoff in the dark. Test it once a year so you're not learning it during a burst pipe.
• Water leak detection tablets ($8). Drop one in the toilet tank to check for a slow leak. A leaking flapper wastes thousands of gallons a year without you knowing.
• Faucet cartridge removal tool ($12). Makes swapping a cartridge cleaner and faster. Not essential — a screwdriver works — but it's worth it if you have multiple faucets.

How to know your shutoff valves

Before you need the shutoff, know where it is. Every fixture has a stop valve underneath (sink, toilet, shower — not always, but usually). The main shutoff is in the basement, the crawlspace, or buried in a meter box in the yard. Find it, trace the line, test the valve twice a year (turn it off and on slowly — stiff valves can jam if you're rough). The 10 minutes spent knowing this now saves you from a panicked 2am search.

Fixture stop valves

Look under the sink, behind the toilet, or behind the wall where the shower line enters. The stop valve is small (quarter-size), with a turnkey handle. It controls water to that fixture only. Turn it clockwise to close, counterclockwise to open. If you can't find it, it either doesn't exist (older homes, some shower lines) or it's behind the wall. In that case, use the main shutoff for that fixture.

The main shutoff valve

This is your most important repair tool. It's usually one of three places:

• Basement or crawlspace: Look where the main water line enters the foundation. You'll see a larger valve with a round handle (wheel valve) or a lever handle. Some homes have a backflow preventer in this spot too.
• Yard meter box: If you don't see it inside, look outside. The meter box (concrete or plastic square in the ground near the street) often contains the main shutoff. A meter box key ($15) helps you reach it in the dark.
• Wall near the front of the house: Newer homes often mount it here — a small box on the exterior with a handle inside.

Test it before you need it

Once a year, turn the main shutoff off and on again. This prevents the valve from seizing — a closed valve that hasn't moved in 10 years might be impossible to turn in an emergency. Turn slowly. If it feels stuck, don't force it; spray with WD-40, wait 10 minutes, try again. Know the feel of it so you're not guessing at 2am when a pipe bursts.

Bylines on this page

Marcus Webb, Columbus, Ohio — Trade contractor, 16 years. Plumbing is Marcus's lane; everything here is tested against trade reality. When Marcus says "don't," listen.

Dana Cole, Austin, Texas — Design background, opinions on how things ought to work. Dana believes the fixtures should be beautiful and the repairs invisible.

Ray Torres, Phoenix, Arizona — Building inspector and safety first. Ray's voice is the calm one asking "did you check the shutoff?"

Iris (Editor's Pick) — AI-assisted guides built on demand. How to Fix a Leaky Faucet is the guide most homeowners search first; Iris owns that one.

Sister trades

Plumbing is one of nine trades in the HowTo: Home Edition network. If this trade isn't what you needed, the others are:

• Electrical — The other side of the wall. Wiring, outlets, panel work.
• Painting — The trade that transforms a room. Walls, trim, cabinets, tile.
• Drywall — Patch, tape, float, finish. The backbone of interior repairs.
• Carpentry — Framing, trim, doors, cabinets. The structural and visible work.
• Tile — Backsplash, bathroom, floor. The surface that lasts 30 years.
• HVAC — Heat, cool, breathe. The invisible infrastructure you depend on.
• Roofing — Shingles, flashing, pitch. The first defense against weather.
• Foundation — The base. Cracks, settling, moisture control.