I want a cleanout access port for our aluminum freshwater tank because even after multiple cleanings we continue to have a lot of white crystals in our plumbing. These things result in clogging up the filters. In addition we get a foul odor if we leave the boat for more than a few days. I would like to cut a hole in the aluminum tank and install an access port. It seems to be a straightforward job but wanted to see what tools and techniques people here would recommend.