The line between a repair you should learn and one you should pay for is drawn by consequence, not difficulty. Swapping a toilet flapper and landing wires in a service panel take similar hand skill. They differ in what a mistake costs: a wet floor versus a fire. Sort failures that way and a short list lands on your side. Five repay the learning hour fastest, because a trade bills a minimum callout whether the visit runs ten minutes or ninety, while the parts below cost 3 to 30 dollars.
Quick answer: Learn to replace a toilet flapper or fill valve, replace a faucet cartridge or washer, realign a door that will not latch, redo failed caulk at a tub, and swap a worn light switch. Parts run 3 to 30 dollars and each job takes 20 to 60 minutes. All five need a shutoff you control, a water stop or a breaker. Gas, structure, and anything inside the service panel stay with a licensed pro.
How to tell a repair is yours
Four questions sort almost every failure in a house.
Is there a shutoff you control? A stop valve under the fixture, a breaker in the panel. If making the part safe means cutting service to the whole building, the job is not yours.
Is the broken piece sold as a part? Flappers, cartridges, strike plates, and switches hang on a hook at any hardware store, and a manufacturer selling the piece expects an owner to fit it.
Does a mistake stay small? Bad caulk scrapes off in ten minutes. A cross-threaded gas fitting does not undo itself.
Can you restore service the same day? Learning on the only toilet in the house, at bedtime, is how a repair becomes an emergency.
All five need one small kit: a multi-bit screwdriver, an 8-inch adjustable wrench, tongue-and-groove and needle-nose pliers, a utility knife, a caulk gun, and a non-contact voltage tester. Two more jobs pass the same tests, unclogging a drain and patching drywall holes.
Repair 1: a toilet that runs
A toilet that hisses, refills on its own, or ripples in the bowl is leaking tank water around the clock. Identify the failed part first. Tint the tank with food coloring and leave the toilet unflushed for 20 minutes. Color in the bowl means the flapper is not sealing. A clear bowl, plus water trickling into the overflow tube in the middle of the tank, means the fill valve sits too high.
For the flapper, close the supply stop behind the toilet by turning it clockwise, then flush and hold the lever down to empty the tank. Unclip the chain, slide the flapper’s two ears off the pegs at the base of the overflow tube, and take the old one to the store to match it. Flappers come in 2-inch and 3-inch sizes and cost 5 to 12 dollars. Fit the new one, reconnect the chain with about half an inch of slack, and open the stop.
A fill valve is a 20-minute job and 12 to 20 dollars. Sponge out the last inch of water, put a bowl under the tank fitting, disconnect the supply line, and unscrew the plastic locknut underneath. Set the new valve so its top sits at least an inch above the overflow tube, snug the locknut by hand and add a quarter turn, then clip the refill hose to the overflow rim so its end stays above the water, never inside the tube. Adjust the float until water stops an inch below that rim.
Repair 2: a faucet that drips
A drip from the spout tip is a worn valve. Water seeping from the base of the spout is a worn O-ring, a different and easier fix. Either way, close both stops under the sink, open the faucet to release pressure, and stuff a rag in the drain so a dropped screw stays in the room.
Single-handle faucets use a cartridge. Pry the cap off the handle, back out the handle screw, often a hex head, and lift the handle away. Under it sits a retaining clip or a bonnet nut. Pull the clip with needle-nose pliers, then draw the cartridge straight up, twisting if it resists. Cartridges are brand-specific, so match the old one by shape at the counter, 10 to 25 dollars. Coat the new O-rings with silicone plumber’s grease, never petroleum jelly, which swells rubber. Seat the cartridge in the same orientation and open the stops slowly.
Faucets with separate hot and cold handles use compression stems. Unscrew the bonnet nut, lift the stem out, and replace the flat rubber washer held to its base by one brass screw. Washers cost pennies. If the drip survives a new washer, the brass seat below is scored, and a seat wrench plus a matching seat, around 10 dollars, finishes it.
Field note: Shutoff valves are the weak point in all of this. Multi-turn stops seize with age, and the first turn in a decade sometimes leaves one weeping at the packing nut. Find the main shutoff for the house or unit and confirm it moves before any water repair. A stuck stop is then an inconvenience instead of a flood.
Repair 3: a door that will not latch
Diagnose it in ten seconds. Rub the tip of the latch bolt with a pencil, push the door closed until it stops, and open it again. The graphite mark on the strike plate shows where the bolt is landing: high, low, or short of the hole.
A low mark almost always means the door has sagged, and the top hinge is usually the reason. Lift the weight off the door and tighten the hinge screws in the jamb. If a screw spins without biting, the hole is stripped. Replace one screw per jamb leaf with a 3-inch screw that reaches the framing behind the jamb. That screw pulls the top of the door toward the hinge side and often lifts the latch back into line.
If the bolt still misses by a hair, move the target. A gap under 1/16 inch files out: unscrew the strike plate, clamp it, and take metal off the inside edge of the opening until the bolt clears. Anything larger means moving the plate. Pack the old screw holes with glue and toothpicks, let them dry, then drill fresh pilot holes 1/8 inch over and pare the mortise with a chisel.
A bolt that lines up but will not extend is dirty. Spray dry lubricant into the mechanism, work the handle 20 times, and wipe the excess. Skip oil, which collects grit.
Repair 4: failed caulk at a tub or sink
Cracked or blackened caulk where a tub meets the wall is a water-damage problem wearing a cosmetic disguise. Redo it before the surface it hides turns soft.
Remove every trace of the old bead. Score both edges with a utility knife, pull the bead out in one strip, and scrape the residue with a plastic caulk tool. Silicone will not bond to old silicone, soap film, or mildew, so wipe the joint with rubbing alcohol. A moldy joint gets diluted bleach first, then a rinse and a full day to dry.
Fill the tub with water before caulking. A loaded tub settles lower than an empty one, and a bead applied to an empty tub tears the first time someone steps in. For a shower pan, stand in it.
Use 100 percent silicone rated for kitchen and bath, not the paintable acrylic meant for trim. Cut the nozzle at 45 degrees to an opening about 1/8 inch, mask both sides of the joint 3/16 inch back, and lay one continuous bead, pushing the gun ahead of the nozzle rather than dragging it. Tool the bead once with a wet fingertip, pull the tape while the silicone is wet, then leave it alone. Give it 24 hours before running water.
Repair 5: a light switch that has failed
A switch that buzzes, feels mushy, needs a second push, or runs warm has worn out its contacts. The replacement costs 2 to 5 dollars and 15 minutes.
Do the safety steps in sequence and skip none of them. Kill the breaker feeding the switch, not the switch itself. Take off the cover plate and hold a non-contact voltage tester against every wire in the box, including ones unrelated to the switch, since a box sometimes carries two circuits. Confirm the tester chirps on a live outlet before trusting its silence.
Photograph the wiring before loosening anything. A single-pole switch has two brass screws plus a green ground screw, and its two hot wires are interchangeable. Three screws plus a ground means a three-way, running one light from two locations. One screw is darker: that is the common terminal, and the wire on it must land on the new switch’s common terminal. Flag it with tape first.
Transfer one wire at a time. Use the screw terminals; the push-in holes on the back loosen with age. Strip 3/4 inch of insulation, bend a hook with needle-nose pliers, loop it clockwise around the screw so tightening closes the hook, and snug it down hard. Land the bare or green conductor on the ground screw. Fold the wires into the box in a flat accordion, mount the switch level, and restore power.
What to hand to a professional
Three categories stay off the list no matter what a video suggests.
Gas is the first. Do not loosen, tighten, or reroute any gas line, connector, or appliance fitting, including the flexible connector behind a range. Pressure testing is not a homeowner procedure. If you smell gas, leave the building and call from outside.
Structure is second. Anything carrying weight belongs to a contractor: cutting a joist, notching a stud past code limits, removing a wall, reframing an opening. Sagging floors and doors falling out of line across a whole house are symptoms, not projects.
Major electrical is third. The service panel is closed to you, including adding a breaker. Past the panel, call an electrician for aluminum branch wiring, crumbling cloth insulation, scorch marks inside a box, a box with no ground, or a circuit that trips whenever one load switches on. Replacing a switch or a fixture is maintenance; adding or moving circuits is licensed work in most places, and unpermitted work surfaces when you sell or file a claim.
The five above that line are ordinary maintenance, and only the first attempt costs an hour instead of twenty minutes. Buy the part first, confirm the shutoff turns, and pick an hour nobody else is waiting on the bathroom.