Fitting holding tanks

Re: Hmmm...

Thanks for the correction, Nigel. I'm not sure where my misinformation that the difference between US and Imperial gallons was based on quarts vs. liters came from...'twas some time during the abortive efforts to convert the US to the metric system.

Your tank looks good, Steve. As long as the walls are thick enough to support the weight of the contents, it should last indefinitely. The hose connections should have two clamps, though...and I HOPE the photo was taken before the vent line was connected...'cuz waste tanks must be vented to the outside of the boat. US regs require it...if ISO regs don't, they should...'cuz methane is flammable and the gasses--sulfur dioxide and hydrogen sulfide--generated by anaerobic breakdown are toxic, even lethal in high enough concentration in an enclosed space.
 
Re: Hmmm...

Yes, when I said 'before' and 'after' I meant after installation of the tank itself. The fittings aren't complete in the second photo. It's all double-clipped now, including of course the overboard vent.

Although I've seen your previous advice to use a 1.5" vent to get as much oxygen to the tank as possible, I could only use a 3/4" vent due to installation constraints but it does seem to be adequate in this case. I made sure that the vent pipe stays clear and drains any fluids back to the tank so maybe that helps.
 
Stainless steel corrosion resistance.

Its time to confess one of my sins. One Friday afternoon at work I left stainless vessel (about 4 mm. thick and very good stainless) full of a gelatin solution with a concentrated salt solution stagnant in a stainless steel pipe in the solution. By Monday morning I had a pie corroded away and a hole in the tank too. Thats the combination of chloride ions, rotting gelatin (reducing environement rather like sewage) .
OK that salt soluton was mch stonger than sea water but the hole took 2 days max.,
Stainless corrosion depends on weld quality , stainless quality, scratches but above all usage. I use my boat solidly for 2-3 month a year. It wears quite quickly. Most boats are used very little and the holding tanks even less.
Remember even a small hole will make a very nasty mess.
 
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