I knew we were living on borrowed time, with the original aluminum holding tank on our '92 Hunter 33.5. Probably past borrowed time actually, because we already had some smell which was mostly under control. The previous owner had made some repairs to the tank, but I can't recall what he said he did.
Wanting to replace the tank on my time, and not as an emergency, I started the planning process of replacing everything, from the head (from Jabsco to Raritan
PH SuperFlush), the hoses (original to
Raritan Saniflex, with Shields for the vent hose), the tank (original aluminum to Ronco), and the airlock.
The holding tank is under the starboard settee, just on the other side of the wall from the head. With
Ronco's help I was able to get tank of equal capacity (20 gal) which would fit, though of slightly different dimensions. My first mistake was to have Ronco give me threaded fittings the same places as the original tank. After it arrived I realized it would be nearly impossible to find compatible low profile fittings which would still fitter under the seat. I did find some good information in several of Peggie's posts about the
Uniseal fitting and decided to go that way. At first I thought I'd have to order another tank but it occurred to me that I could plug the threaded fittings Ronco provided and flip the tank around. I also had Ronco weld flanges on the bottom of the tank to mimic what the original tank had. These would allow me to screw the tank to the floor, just like the original.
The next challenge was to find the right fittings to keep a low enough profile. The magic combination was the 2" Uniseal, this
1.5" flange fitting, and this 90° sanitation
hose fitting found at West Marine. The 1.5" flange fitting allowed me to cement a 1.5" PVC dip tube to the bottom, screw on the hose fitting using teflon tape, then press it into the Uniseal. The Saniflex hose easy went on the hose fitting and was well secured by double hose clamps. Saniflex is a wonderful product. Highly recommended for easy of installation.
I used the same parts for the connection to the head, but without the dip tube, of course. For the vent, I had to come up with a different assembly since I couldn't find the parts above in 3/4". I used a 3/4" PVC pipe to insert in that Uniseal but ended up cutting it too short so I need to rebuild that assembly. Speaking of the vent, I did not up-size it based on Peggie's advise because I had already bought everything when I read that. It would be easy enough to do that later if I decide it's needed.
Last fall, when it finally came time to do it, I flushed a LOT of fresh water through the head, then had the marina do a double pump out, first as is, second after filling up with fresh water again. It turned out the tank started leaking that day. It didn't stink terribly so I suspect it was from the fresh water in the tank...perhaps they overfilled before the second pump out.
The demo work went smoothly and wasn't nearly as odoriferous as I expected. When I pulled out the old tank, however, it was wet underneath. I sprayed the area down with something (I can't recall what) wiped as much as I could. While removing the old hoses I decided the best thing to do would be to wait until spring to install the tank to give it a chance to thoroughly dry. I did install all the hose I could, leaving only the head-to-tank hose and the final connections on the rest to complete this spring. I also installed the new head, which used the same mounting holes as the old head, but a problem came up there which I'll post about separately, because I need some advice on it.
Saturday I took the shrink wrap off the boat and was happy to have NO smell inside! I installed the tank and made most of my final connections but as I mentioned, i need to replace the vent hose fitting, make the final connection and I have an issue with the head position so I need to solve that and then install the head-to-tank hose.
