If the hot water running out of your tap seems yellow or brown, or if the pool of water in your bathtub has dirt or gunk floating around, flush your heater to remove all sediment.

Cool water doesn't run through your water heater, so if you notice that even cool water seems discolored or rusty, the issue is likely with your pipes or the city's water supply.

Noises like popping, banging, or hissing indicate that too much air is trapped in the tank or that the water can’t move freely because of all the sediment building up inside.

Noises loud enough to be heard from the main living area are a sign of trouble. To be sure, turn on a hot shower and immediately observe the water heater for unusual noises.

If you like a certain amount of water pressure, you can typically control it with certain fixtures. However, if things suddenly slow to a trickle, you’ll need to flush the heater.

Low water pressure due to an unflushed water heater typically builds up over time. However, if you’re lucky enough, it’ll happen overnight, allowing you to fix the issue promptly.

If your hot water smells like rotten eggs or sulfur, or tastes like metal, there is too much bacteria in the pipes, and you must flush it out.

Potential bacteria include Legionella (which causes a severe form of pneumonia), Pseudomonas (which causes skin infection and respiratory issues), and E. coli.

Water that is still freezing after a minute of waiting could mean the tank is clogged. However, if flushing the water heater doesn't speed things up, you’ll need other solutions.

If you're walking into cold showers for at least a week, it might be time to call a plumber. If it only happens once, it might just mean you have already used up all the hot water.