My new boat has a marine head with a 13 gallon holding tank. This is the first boat I have owned with a marine head, so I have a couple of questions. First, can anyone suggest any deodorizer that can be added to the head and holding tank. We noticed this weekend some smell coming out of the vent at the stern when the head was being flushed. Second, we have not yet had to pump out the head. On our lake there are only self serve type pump out stations at the marinas. Can someone give me some basic instructions on how to pump out the waste. The only ballcock valve my head has is the one that lets water into the head via the through hull fitting. Thanks for any constructive help you can provide.