One of the most common question we often get is "Can I wash a dyson dc07 hepa filter?" Before answering this question we are assuming that you are referring to the Dyson post motor HEPA filter which is below the dirt bin like the picture below location on Dyson DC-07 Hepa Filter

The answer to this is - NO you can not.

Unlike the pre motor yellow pre filter, which is on the side of the vacuum, the HEPA filter is not washable. It has HEPA media which gets destroyed when the filter is washed or rinsed with water.

This filter is recommended to be changed every 6 months or so (depending on how much you vacuum). 

This also applies to the post motor hepa filter for Dyson DC14 & DC15 Dyson DC07/DC14/DC15 Spare Hepa Filter 901420-02 - Generic