artar

I own a monterey 275 scr. in my countrey i am allowed to dump the waste to the sea when you are away 12 miles. But i couldnt figure out how? there is a black button on the toilet that you have to hold it down and seacock has to be opened right ? However i read the manula, it is also talking about discharge valve? i couldnt locate the valve. did i understood wrong? both discrage valve and seacock has to be opened inroder to pump out ? any help, id appriciate it. thank you so much