In the past we stayed for several months in the same RV park in our MH. We used Exodor Bio-Pak drop ins for the black and gray tanks. Sometimes there was a horrible eggy smell when we dumped the gray ...
Dump your tanks every three days especially in the heat of summer. After dumping, add several gallons of water to the black tank before using. Also, I dump my tanks when in transit to prevent any build up on tank walls. We do not need to use a tank treatment due to frequency of dumping.