PVC is permanent and NEVER smells.
And, yes, it will stand up to more abuse than you can willingly give it; ours survived our wreck with 3-5000 impacts at a 60į heel on the side with the PVC, in 8-10' surf over 3 days.
From Peggie Hall (Princess of poop, Head
Mistress), you'll also never have scale (nor smell, for that matter) if you:
Flush continuously while inserting 'product of eating' as well as per square of TP (which will assure that any urine products are rinsed, leading to no scale buildup, even in salt water
Followed by however many (calculate) strokes it takes to move whatever is in the pipe past the anti-siphon valve (downhill all the way after that, which will bring the water
level in the pipe to the outside water
level, leaving a bit of air at the top),
Followed by the same number of dry strokes, which, if your anti-siphon valve works,
Leaves you with a dry stack.
I've had occasion to service
my Y valve on occasion (new depth sounder
under it, broken and replaced in another) and after 11 years of relatively constant use, have still found the pipe at the Y empty of scale, with only the slightest darkening of the bottom (no material).
Here's a pic of that installation
; the white pipe in the lower left is what connects to the new Y:
Pictures: Flying Pig Refit 2011-2012/Fishfinder and SSB Redo
Here's the entire rebuild
with the new Y valve some years later, with a better pic of the PVC end (photo ending in 91):
Pictures: Flying Pig Shakedown 2013-2014/Y-Valve and Hose
And a closeup of that PVC end:
As to head smell...
First, determine where the smell's coming from. Even expensive hose will eventually pass odor
, but if it's new, it shouldn't smell. Determine hose as the source by taking a warm damp rag and wrapping it around the suspect area. Wait a minute or two and then give it a sniff. If there is the slightest odor
it's the hose, otherwise keep looking.
I can't do anything about vents to holding tanks
; see the link to Peggie's controlling boat odors for that.
However, PVC will solve everything else. It's a bit fiddly (the reason they use hose rather than PVC is that it's labor intensive to plot out the twists and turns needed vs just running the hose, particularly in the construction phase where lots of stuff may not yet be in the way.
My apologies for all the other stuff going on but here's the link to my installation
of the forward head's pipe (the one you see in the other pix)
Pictures: Flying Pig Early Refit + Projects/Early_Major_Alterations_Work/04-05
Dang. That just shows the pieces. More here:
Pictures: Flying Pig Early Refit + Projects/Early_Major_Alterations_Work/04-26&27-05