Put the plug in the hole which stops dirty water going into the bio chamber, turn the pump off and close the intake valve, switch the air on to clean cycle and let it go for twenty mins or so, then drain:
[YT]<object width="640" height="385"><param name="movie" value="http://www.youtube.com/v/LM8TbZpaF-4&hl=en_US&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/LM8TbZpaF-4&hl=en_US&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="640" height="385"></embed></object>[/YT]
Then this is what you drop to waste:
[YT]<object width="640" height="385"><param name="movie" value="http://www.youtube.com/v/LM8TbZpaF-4&hl=en_US&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/LM8TbZpaF-4&hl=en_US&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="640" height="385"></embed></object>[/YT]
Then this is what you drop to waste: