You hear the toilet running before you have your coat off.

Dad hears it too. He gives the handle a practiced jiggle, waits for the water to stop, and looks at you as if the matter has been settled by a man who has negotiated successfully with this toilet for years.

Maybe it has. A running toilet can come from a small part inside the tank that you can replace without turning the bathroom into a construction site. It can also be the first clue that an old shutoff valve will not close, the tank is cracked, or the toilet moves when someone sits down.

The decision is not whether you are handy. It is whether this is one contained repair with a working way to stop the water.

Start with the exact thing the toilet is doing

Ask Dad to show you what happens instead of asking whether the toilet is broken. He may say it is fine because it still flushes. That is a fair definition from the person who needs to use it.

Flush once and watch the whole cycle with the tank lid off. Set the lid flat on a folded towel, not upright against the tub where one bump can break it.

Look for these simple patterns:

The flapper lifts, drops, and does not seal until the handle is jiggled. The chain may be too tight, too loose, or caught under the flapper.

Water keeps spilling into the open tube in the middle of the tank. The fill level or fill valve may be the problem.

The handle feels loose or stays down. The lever or chain may be binding.

Water appears on the floor, the tank looks cracked, or the whole toilet rocks. Stop treating this as a tank-part project.

Do not add tablets or cleaners to the tank while you are trying to understand the problem. They can color the water and make a slow leak harder to see.

Test the shutoff before choosing the do-it-yourself repair

The small valve behind or beside the toilet is your exit from the job. You need to know it works before taking anything apart.

Find the valve with Dad. Put a dry towel underneath it. Turn it gently toward closed without forcing it. Flush the toilet. If the tank does not refill, the valve is doing its job.

Now look and feel around the valve and the pipe connection with dry fingers or tissue. If water appears, reopen the valve gently and call a plumber. If the valve will not turn, spins without stopping the water, or needs a wrench and considerable determination, leave it alone. This repair has already moved beyond a flapper.

Also find the home's main water shutoff and make sure both of you know where it is. You do not need to operate it merely to prove a point. You do need a plan if a fitting begins leaking while the toilet valve is open.

When doing it yourself makes sense

A do-it-yourself repair is reasonable when the problem is clearly inside the tank, the porcelain is intact, the toilet is steady, the local shutoff works, and you can reach everything without straining or kneeling uncomfortably.

Take a photo before removing a part. Photograph how the chain attaches and where the water level sits. If you buy a replacement, bring the old part or clear photos and the toilet's identifying information. Similar-looking tank parts do not always fit or move the same way.

Change one thing at a time. Do not replace the flapper, adjust the float, shorten the chain, and bend the handle lever all at once. You will not know which change helped or which one created the next problem.

After the repair, turn the water back on slowly. Flush several times. Let the toilet sit quietly, then check the floor, valve, tank bolts, and the space between the tank and bowl with dry tissue. Come back later and check again.

Let Dad do the final flush. It is his bathroom, and he knows how the handle normally feels. A repair is not finished merely because the tank becomes quiet while you are watching it.

When to hire it out

Call a plumber when the toilet rocks, water is reaching the floor, porcelain is cracked, the shutoff does not work, tank bolts are badly corroded, or the problem returns after a straightforward tank repair.

Hire the work out if reaching the valve requires crawling behind the toilet, if either of you would need to lift the toilet, or if the only plan for a stuck connection is to pull harder. Old plumbing can turn a small repair into a larger one without offering much warning.

When you call, describe what you actually observed: the toilet runs after flushing, jiggling the handle stops it, the shutoff does or does not close, and there is or is not water on the floor. Ask whether the visit covers diagnosis only or also a common tank repair. Ask what approval the plumber needs before doing additional work.

If the plumber recommends replacing the toilet, ask what cannot be repaired, whether the floor or flange is damaged, and whether the shutoff valve should be replaced at the same time. Ask who removes the old toilet and who checks for leaks after the new one is installed.

Dad should be part of that conversation. He may care about the seat height, handle location, bowl shape, or how forcefully it flushes. Those are not decorative details when he uses it every day.

What to do tonight

Listen for the toilet to run when no one has used it. Remove the tank lid safely and watch one flush. Check the floor and the base with dry tissue. Test the local shutoff gently, but do not force it.

If water is on the floor, the toilet moves, or the shutoff begins leaking, stop the experiment. Close the water only if the valve moves normally, put down towels, and arrange repair help. Make sure Dad has another usable toilet before leaving the water off.

If the trouble is plainly a tangled chain or a flapper that is not settling, make one small adjustment and test it several times. Leave Dad a toilet that works tonight, not a row of parts on the bathroom floor and a promise to finish later.

When to ask the doctor

The toilet repair itself is not a doctor question. A change in how Dad uses the bathroom can be.

Ask his doctor if Dad is suddenly rushing to the toilet, having new trouble getting there, avoiding fluids because he fears an accident, becoming dizzy when he stands, or struggling to sit down or rise. Describe the change you saw and when it happens. Do not let a noisy toilet hide the fact that the route, timing, or movement has become hard for him.

Add this to the good-week card

The toilet finishes a flush, stays quiet, and the floor remains dry.