eufy WetVac W31 is designed to clean debris and excessive liquids. Generally, any water stains left by the WetVac will be completely dry after a few minutes.

If there is water stain left by the WetVac, please verify the following details:

1. Make sure the sponge filter is completely dry before using the vacuum. A wet sponge filter will affect the vacuum's suction and mopping performance, which can potentially leave water stains on the floor.
2. Please do not press the water spray button before powering off the WetVac, simply run the WetVac for a few seconds before setting the handlebar to an upright position.

If you need any further assistance, please contact us.