IP67 protection class ensures that a device is protected against the effects of immersion in water. It can happen by accident during standard operation of a device. It does not mean that a device can be used under water or cleaned under high pressure of water. IP67 class allows for immersing small devices in 1m deep water for up to 30 minutes.
If a device is going to be used under water permanently, a device compliant with IP68 should be bought. Restrictions connected with IP class must be specified by a manufacturer individually.
When there is a need to use pressure washing, it would be good to decide on products with IP66K or IP69K protection class. In the first case, a device is protected against effects of immersion in water for a very short period of time.
It should be mentioned that IP67 class ensures full dust-tightness of products.