Hot water that runs out sooner than it used to is a change in the system or in the household. It is worth recording before anyone decides what it means. This piece walks through how to recognize the change and what to check first.
Recognize the change
The signs are familiar. A full bath that used to be possible now ends in cold water partway through. The shower turns cold within a few minutes when someone else runs the washer or dishwasher. Water from the far fixtures is lukewarm while the nearest tap is hot. Any of these describes a smaller amount of usable hot water. None of them is a diagnosis yet.
Check what changed in the house
Before you look at the tank, look at the household. Count who uses hot water now, compared with the last time the supply felt right. Note any new appliance on the hot line, a longer bathing routine, or a new laundry schedule. A change in demand can explain a shortfall without any fault in the unit.
Check the set temperature safely
Look at the setting on the tank or its controls. Do not raise the setting to compensate, because water at high temperature can scald quickly. If the setting has been moved, note the original and return it to where the maker's instructions suggest. If the control is hard to read, ask a technician to label it.
Write down the pattern
Record what you see in a short log: which fixtures run cold, how long the hot run lasts, whether the change came gradually or in steps, and whether the sound of the unit changed at the same time. Note whether the water is lukewarm at the tank or only at the fixture. The pattern is what a technician will want to see.
Decide what to ask
Ask the technician whether the recovery rate matches the household's use, whether the heating element or burner is working as designed, and whether sediment is limiting heat transfer. Ask what the unit's age means for planning, and whether repair or replacement is the sensible next step for the house as it runs today. Age is a planning input. It is not a verdict on the tank.
Safety first
If you smell gas near a gas unit, leave the house, then call the gas utility or emergency services from outside. Do not open the gas valve or the burner access to look. Before any electrical unit is serviced, turn its breaker off and confirm the power is off before opening a panel.