How can you tell if your car's water pump is bad?

Not sure what sort of car we're talking about. On some cars, the heater isn't in circuit until the thermostat opens.

Water pumps usually fail at the bearing. The telltale is either a leak or a squeeky sound. If the impeller or involute is bad, you would have overheating at speed.

Just put everything back together, don't worry about it unless there's a problem.

Usually when a water pump goes bad, it begins to leak. There is a small weep hole in the casting that will drip once the inner seal has started leaking. If that is not caught in time, the bearing will fail and the water pump shaft will begin to wobble or make a noise.

The only other possible problem with a waterpump is if the impeller has broken or come off the shaft. That might be hard to detect without removing the pump. The fact that your engine is not overheating would tend to rule that out.

what made you decide to drain your cooling system? Was there a leak? I doubt anything is wrong with your pump, they usually go out all the way when they go out.

Also, you shouldn't be putting garden hose water into your engine the mineral deposits will cause buildup. always use distilled water.

Simple answer.....After the car has cooled off, take the radiator cap off,make sure its topped off. Start the car, have some one rev the motor while you watch the level in the radiator. As the motors rpm's increase, the level in the radiator should decrease. And you should see the coolant flowing inside the radiator.