Most of the eventual cost of a water event is determined in the first couple of hours, and most households spend those hours doing things in an order that makes the outcome worse. Not through panic. Through doing the obviously useful thing, such as moving furniture, before doing the invisibly important one, such as photographing the room it was standing in.
Here is the order. The first three protect people, the next three protect the building, and the last four protect the claim.
1. Shut off the water
The house has a main shutoff, usually where the supply enters, often in a basement or a crawl space or at a meter near the street. Individual fixtures have their own. If you do not know where yours is, that is the sentence in this piece worth acting on today rather than in an emergency.
Where the source is a supply line, an appliance, or a fixture, the local valve is faster. Where the source is unclear, close the main and work it out afterward.
2. Cut power to the affected area
Only if you can reach the panel without standing in water. Water at outlet height, water at the panel, water coming down through a ceiling that has lights in it: each of those is an electrical hazard first and a property problem second, and this is the one step where the right answer may be to leave the building and call somebody.
3. Get people and pets clear
Particularly where the water is not clean. Sewage backup and floodwater from outside carry contamination that changes what can be salvaged and how it has to be handled. If the source is a sewer line or standing water from outside the building, treat everything it touched as contaminated and do not try to clean it yourself.
4. Photograph everything before you move anything
Under sixty seconds and the highest value minute of the entire process. Wide shots of each room first so the damage can be located, then closer shots. Photograph the source. Photograph the water level against a wall or a cabinet. Photograph belongings where they are standing.
Everything after this step disturbs the scene, and a claim that arrives with photographs of the room before the cleanup is a different conversation from one that arrives with a description of it.
5. Stop it spreading
Now the physical work. Towels and a wet vacuum on hard surfaces. Extract standing water rather than pushing it, and prioritize keeping it out of rooms it has not reached, since a dry room stays cheap and a wet one does not.
Doorway thresholds and the tops of stairs are where a contained problem becomes a whole floor problem.
6. Lift what is standing in it
Furniture legs on wet carpet transfer stain and finish into the carpet within hours, and wooden feet swell and delaminate. Slide foil, plastic, or blocks under them. Get anything absorbent off the floor entirely: boxes, books, papers, fabric.
This is also the moment to move anything irreplaceable somewhere dry, which is a small task that people are grateful for later.
7. Call the insurer and get a claim number
Even if you are not certain you will claim. Prompt notice is a condition of nearly every policy and the number gives you a reference for everything that follows. Ask what they need, whether they will send an adjuster, and whether they want to approve a restoration company or whether you may choose one.
Ask also what emergency mitigation costs are covered, because acting to prevent further damage is generally both required of you and reimbursable.
8. Get air moving and start removing moisture
Fans across surfaces rather than pointed at one spot, and a dehumidifier running in a closed space rather than with the windows open, unless the outside air is genuinely drier than the inside air.
Open what you can. Cabinet doors, closet doors, the toe kick under cabinets. Air that cannot reach a wet surface does nothing for it, and the cavities are where the water actually sits.
9. Keep the receipts and keep the evidence
Every receipt from the first hour on: the wet vacuum you bought, the fans you rented, the hotel if the house is not habitable, the meals if the kitchen is out. Keep a piece of the failed part, the hose, the section of pipe. Keep a sample of the removed material.
Those physical items answer causation questions later that nobody can settle from memory.
10. Write the timeline before you sleep
One page. When it started as best you can tell, when it was found, who you called and at what time, what you did. Written the same day, while it is exact.
This is the document that gets referenced for the next six months by you, the adjuster, and the contractor, and it is the only one that cannot be reconstructed later.
What to have ready before any of this
Three things, and none of them take an afternoon. Know where the main shutoff is and check that the valve actually turns. Know where the electrical panel is and which breakers serve which rooms. And keep the insurer's claim number and your policy number somewhere reachable from a phone.
Households that have those three tend to describe the same event as an expensive inconvenience. Households that do not tend to describe it as the worst week of the year. Ready.gov is the federal public preparedness resource and its household checklists cover the same ground for every other kind of emergency, which is worth an evening at some point when nothing is happening.