Found the vacuum leak in the sanitary system
A little background: The boat is a 76 Viking. When I got her a few years ago, she still had a few legacy systems. The sanitary system was originally one of the 70s style that serviced two heads. Vacuum transferred waste to an ≈ 40 gallon holding tank. There, through an amazing rat’s nest of wiring that connected to a cover plate with an attached probe, some sort of electrical and magical waste treatment was supposed to occur prior to overboard release. I don’t recall the name of the system – long gone company.
I ripped out the electrical and salvaged the nice F/G holding tank, vac system. Installed new 3 way and hosing. Kept the old but very serviceable commodes. And found that I had a persistent vacuum leak that required the vac pump to run for the system to work. I further discovered that I could eliminate the vac leak by isolating the aft head from the rest of the system. So, I had a performing one head system. That was fine for the limited pax loading that I use. So, the vac leak migrated lower on the “to do” list and stayed that way for a couple of years.
However, the leak was an irritant, so considerable time was spent on an off and on basis chasing it. Several knowledgeable friends gave it a try. Replaced clamps, a valve or two, hose, commode base seal, etc. Still leaked. I finally turned the problem over to the yard I use for stuff I can’t handle. Their old mechanic (guy in his 70s – my age) went straight to the aft head, pulled the commode, and fought with the “funnel” below the deck until he recovered it. The results are shown below.
The funnel has a brass nipple soldered into its outlet. If you look carefully, you’ll see that the nipple is corroded through for 1/16” or so on its lowest elevation (when installed). The hose was double clamped to the nipple, but without sufficient coverage to bridge the gap. All of this is placed where the nipple/hose penetrates a bulkhead, of course.
I don’t know if this arrangement is still around on newer boats – not likely, I think. But, it may be useful info to somebody who’s wrenching an old boat.
Pics 1 and 2 show the general funnel arrangement.
Pic 3 shows the corroded nipple.