I replaced the forward tank obtained from Triple M Plastics (800) 873-7767 a week ago, good thing as there were several dozen holes, much larger than a pin, more the size of an eraser, that had rotted through the tank on the side facing the hull where they are invisible. Fortunately, because of my instance, we had not used the forward head/tank since we purchased the boat 7 months ago so the waste fluid was not spilling out. After removing the front access panel (see below) I discovered why we were unable to get anything out of the tank even though there was, let's use the term gunk, left in the lower third. The hose from the tank to the through hull pump out had collapsed so we were unable to use the deck through hull to empty the tank. Instead I removed the hose leading from the tank to the macerator after it was unbolted from the wall separating the forward cabin from the head and was able to suck out most of the gunk left in the tank with the pump out hose run through the hatch above the berth.
Once the tank was empty (mostly), remove all the bedding, drawers, lots of screws holding the front panel to the bed frame where the access plate is (there are two in the forward salon to cabin wall by the end of the settee), screws holding the trim pieces in place securing the front panel, screws holding the plywood bed base to the front panel. The front panel should now be loose and can be wiggled downward and forward and removed. Now remove the screws holding the drawer boxes (they are in the pieces of wood that the three access hatches sit on, remove the drawer box (all 3 are in one box), the wood divider between the two tanks has to come out after the trim pieces securing the bed base ply are removed so it can be raised enough to get out the divider (I had to trim this piece slightly to get it back once the new tank was in place).
The screws holding the tank to the hull can now be removed, be careful as they can strip easily (don't ask how I know). Disconnect all the hoses and the tank will lift out watch that any corroded holes in the tank don't allow any remaining waste left in there to spill. The tank is now loose but will not fit through the door unless the salon to forward cabin door and frame are removed, in retrospect I should have remove those first. Save the rubber insulating strips between the tank and hull to use with the new tank and clean everything very, very well.
Installation is the reverse of removal but I would recommend to take the extra time and expense now to replace all the hoses from the head to the tank, macerator and through hulls. Check the operation of the macerator before reassembly, it's a real good time to replace it as well especially if it's original, ours was seized and would not work. I used Sealand Sanitation hose to insure another 20 years of low odor operation. It’s expensive but the admiral will thank you. We also replaced the forward head with a Raritan fresh water head from Defender Industries #(502594 RARI FRESH HEAD - COMPACT BOWL) it fit perfectly in the place of the original, hooks to the fresh water supply by T-ing into the sink with no danger of contamination because of the vacuum break incorporated in the design.
Once all hoses are installed and tightened with double clamps (use new ones, they are cheap insurance) fill the tank and check for leaks. No leaks? Good, now reassemble all the pieces, you did remember what went where don’t you? Again don’t ask.
Sorry there are not any pics to share, as I promised above, my phone decided to go for a tumble before I saved them and all the images were lost. This was a two day adventure but a lot of time was spent figuring out where the screws that held things together were, making several trips to WM and Lowes for supplies, installing the new head, looking for mislaid tools, finding that darn heat gun used to soften the hose, removing everything from the work area would also speed things up, it probably could be done in a single day if everything is on hand and the deck is clear.