Do I need a special liner with these training pants?

For significant accidents, having a backup is a good idea. However, for minor accidents, they absorb quite well on their own.

Do these training pants prevent leaks?

They absorb well for small accidents, but they are not leak-proof. Bigger accidents might eventually soak through. They're effective for minor mishaps.

Can these training pants completely replace diapers?

No, these are not diapers. They have a bit more absorbency padding, but they can't handle a large amount of urine like diapers do. Training underwear is softer than diapers and works well in the transition from pullups.

Can I toss these training pants in the washing machine?

Absolutely! They are machine washable. Although, I'd highly recommend hand washing for a longer lifespan of the underwear.

Are these suitable for nighttime potty training, or will they leak?

No, these aren't ideal for nighttime potty training. They aren't like pull-ups that can handle all-night urine. While they may leak, it's relatively less than regular underwear due to the thick padding.