The basement often brings the service entry, heater, laundry, drains, and overhead piping into one view.
The short answer
Sketch the accessible service entry, meter, main shutoff, water heater, laundry connections, sump equipment, floor drains, and pipes serving upper rooms. Label only what you know. Do not operate utility equipment, open cleanouts, or enter a wet electrical area to complete the map.
What to notice
Start with control points
Record where the known main valve is reached, whether its label is current, and what storage blocks access. Add appliance and fixture valves that a provider has identified. A valve handle does not prove the valve will close or that it controls the expected branch. Have uncertain or deteriorated controls assessed before an emergency.
Separate four kinds of water
Supply lines, hot-water equipment, wastewater drains, and groundwater control can cross the same room. Use different marks on the sketch. A puddle near a floor drain may come from equipment, piping, seepage, or another room. Keep the origin unknown until observation supports it.
Add access and finish constraints
Note low ceilings, finished walls, stored belongings, mechanical equipment, and routes from an exterior door. A repair estimate can change when access requires moving or protecting property. Photograph the overall layout for your record but remove private labels or security details before sending it to an unverified recipient.
One useful question
Should the meter valve be my emergency shutoff?
Do not assume ownership or operating responsibility for a valve near a meter. Ask DWWD or a qualified provider which control belongs to the property and is intended for household use. Record that verified answer on your map.