Everything in a basement is at floor level, including the damage

Almost certainly the main sewer line, yes. The floor drain is the lowest opening in the system, so when the line out to the street or the septic tank is blocked, that is where waste surfaces first. Stop using every fixture in the house immediately, each flush and each load of laundry is feeding it, and call. See sewer line repair.

A sump pump that cycles frequently during heavy rain is doing its job. One that runs constantly in dry weather is either handling groundwater it should not be seeing, or has a stuck float or a failed check valve letting the same water drain back into the pit and get pumped again. The last of those is common, cheap to fix, and burns pumps out early.

A sump pump moves groundwater out of a pit in the floor. An ejector pump moves sewage and waste water from basement fixtures, a toilet, a shower or a laundry sink below the level of the main drain, up to the sewer line. They look similar and they are not interchangeable. An ejector pump is a sealed system with a vent because of what it handles.

Usually a dry trap. A floor drain or a rarely used basement fixture has a water seal in its trap that keeps sewer gas out, and if nobody runs water into it for weeks that seal evaporates. Pour a bucket of water down every unused drain and the smell generally goes within an hour. If it does not, the cause is a venting problem or a failed seal on an ejector pit.

A useful first test is where it is. Water tracking along the joint between the floor and the wall, or seeping through a crack in the slab, is almost always groundwater. Water pooling under a pipe, appearing in dry weather, or coming with a rising water bill is plumbing. The two need different trades, and telling them apart before you pay anyone matters.

Usually, and it is one of the more common projects we see. The determining factor is whether the fixtures sit above or below the level of the main drain leaving the house. Above, and it connects by gravity like any other bathroom. Below, and you need an ejector pump system or an upflush arrangement, which changes the cost and the layout considerably. That question is worth answering before the room is designed.

It sits in the main drain line and closes automatically if flow reverses, so a surcharge in the municipal sewer cannot push waste back into your basement. For properties that have flooded before, or that sit low relative to the street, it is genuinely valuable insurance. It is not a substitute for keeping the line clear.

Because that is where the utilities enter and the floor drain already exists. It also means a tank failure discharges into a finished space, sometimes in the middle of the night. A drain pan piped to the floor drain, and a shutoff you can actually reach, are worth having. See water heater repair.

It varies sharply by region. Full basements are widespread across Northern Virginia and much of the Piedmont and the Shenandoah Valley, common in older Richmond neighbourhoods, and comparatively rare in Hampton Roads where the water table sits high. So a plumber who works statewide has to be equally comfortable with a Fairfax finished basement and a Virginia Beach slab.

More urgent than the same leak elsewhere, purely because of what it can ruin. Drywall, flooring, insulation, furniture, storage and often the electrical panel are all at floor level in a finished basement. Water that would be an inconvenience in a crawl space is a claim in a finished lower level.