How do you do that without the water spilling out? Or do you mean waiting for it to drain, opening it, and then refilling (along with more detergent, having wasted the previous dose)?
The water level in a front loading washing machine is lower than the door seal. The seal only contains splashing water from the agitation. You hit the "pause" button, it stops agitating and unlocks the door, you throw your skidmarks in the washer, you close the door and press "start".
The water level in a front loading washing machine is lower than the door seal. The seal only contains splashing water from the agitation. You hit the "pause" button, it stops agitating and unlocks the door, you throw your skidmarks in the washer, you close the door and press "start".