Peggie Hall wrote:

Sometimes spelled "yacht."

Hmmm...it sounds like she's going to hit the "general instruction
mode"... ;-)

There are a few tricks that make re-hosing a bit easier:

1. As is true of most jobs, planning and prep are 90% of a successful
project.

Told ya LOL

So if the tank is in a completely inaccessible place, or the
plumbing run is ridiculously convoluted, or the tank is much further
than about 6' from the toilet, there is no law requiring you repeat the
same errors. Take the time to investigate how to do it better...if
necessary, cut hatches to create access (it's not hard to do, and worth
the effort)...reroute the plumbing...even move the d'd tank!

None were a concern...at this time. But were I going to the trouble to
reorder & rearrange a whole system access, runs & config, I'd be better
off to rearange it for piping.

2. Before you start, measure the OD (outer diameter) of the
fittings....'cuz some nominal 1.5" fittings are actual 1 5/8"--or
they're metric and slightly larger than 1.5", which can make putting
toothpaste back into a tube a walk in the park compared to trying to get
a 1.5" hose onto 'em. Avoid gray PVC 1.5" tank fittings...use marelon or
nylon fittings. Btw, this anomaly only seems to apply to 1.5"...other
sizes are likely to be true.

Ya think...?

But when you start changing out bronze seacocks afloat because their
(decades-standard & perfectly correct) hose fitting OD is on the fat
side for the new vinyl sadistic hose, lemme know.

3. Removing the old hose and running the new hose can often be made
easier by doing both at the same time: cut the ends of the old and the
new hose as cleanly as possible. Put 'em together on a male-male
connector, butting the ends as tightly as possible...you want the
smoothest unbroken surface possible...Use PVC cement to make sure both
hoses STAY on the connector...do NOT use duct tape--it won't hold if you
hit a snag...hose clamps will get caught on something. When you've got
all the hose pulled through, cut the new hose off behind the connector.

Great tip!

4. Don't try to make any hose bend tighter than it wants to bend
willingly...heating a hose to bend it will damage the hose, resulting in
a kink or even a tear.

....drumming fingers...

Instead, break it and insert an inline radius
fitting. Putting two ends onto a fitting is also a LOT easier than
wrestling a hose around a "corner."

Wasn't an issue, but that inserts a major obstruction to smooth flow, &
is beginning to negate the seemingly sole advantage of hose over a good
piping job...

5. When you're finally ready to start putting hoses onto fittings, it'll
go a lot easier if you warm the hose a bit.

....coulda sworn I went there...

A lot of owners like to put
the end of the hose in hot water for a couple of minutes...I've always
found it easier to use a blow dryer. Use a heat gun ONLY if you know
what you're doing with one...'cuz overheating the hose will damage it.
Lubricating both the hose and the fitting with a little dishwashing
liquid--or better yet, K-Y surgical jelly--will help the hose go onto
any fitting that isn't bigger than it's supposed to be.

The water trick's unworkable in tight spaces & the other 2 require
hi-watt 120vac, which is why the heatlamp gets useful - anything worth
doing takes watchfullness...

6. Double clamp all connections, putting the screws on opposite sides of
the hose--or at least offset a minimum of 90 degrees.

SOP

1) How may anyone effect a voyage repair aboard a small craft at sea
with this stuff?

Do it as PREVENTIVE maintenance before you leave the dock, and you won't
have to do it at sea unless you turn into the "Man Without a Country,"
unable to make landfall anywhere ever again.

I feel this is copout reasoning (not in the personal sense please).

2) Does this material become irreparable with age due to changes in
properties?

No...but sea water minerals can build up in it if allowed to (it can be
prevented), and sooner or later it will become permeated with odor.

I referred to a section of hose which responded oppositely to warming &
could no longer be made to accommodate a fitting it had been fitted
correctly to 27 years ago.

3) Is there some compelling reason why reinforced rubber hose with a
suitable polymer barrier - which requires no heating or dubbing around
& clamps better besides - isn't in general use?

Any hose that would slide onto a fitting without any effort would slide
off almost as easily...and prob'ly would leak too.

You're getting a little creative - "without any effort" wasn't there,
consider the hoses in your vehicle - if it isn't electric or sail
powered. :-)

4) Beyond the obvious end treatments, is there some method of making
larger sizes of this "interesting" but uncooperative & pricy product
more easily routed in tighter spaces/radii?

See 1-5 above.

IOW, "no" - I can accept that.

5) Is there some compelling reason why yacht waste piping doesn't more
commonly employ rigid sched 40 DWV?

Several reasons: 1. unless every connection to any fixed component in
the system (toilet, tank, thru-hull, y-valve, etc) is "soft coupled"
with enough hose to cushion shock and protect from flexing,

SOP - many decades...

hard PVC is
likely to crack, especially in cold weather.

Not. (incompetently piped?)

And then there's the need
for unions in anything but a long straight run. Making all those
connections is so labor intensive that the cost of it compared to just
running hose is too high.

Have you never worked with PVC fittings & layout? It is very fast &
easy.

(yes we know about sweeps &
expansion joints) In the case of blackwater wouldn't it last far
longer & be more vapor-impermeable? (not to mention that you could
*work* on it, pitch it so it'd drain & clean it if/when needed) I'm
not seeing an advantage to a very pricy hose that has R/R issues,
offers no timesavings in fitup, seems dicey to have to deal with at sea
& often (I am told) lasts only 2-3 years.

That's not true...white PVC or black rubber hose can last decades with
no deterioration, provided it hasn't been overheated, bent too tightly
or hasn't been chafed through by poor installation. The only reason most
hose is replaced is because it becomes permeated with odor and stinks.

Which is exactly what I was talking about.

The hose is otherwise fine. As a general rule, the stiffer the hose, the
less likely it is to become permeated with odor...the softer it is, the
more likely. Many owners don't realize that not all white PVC hose is
created equal or rated for sanitation...so they use hot tub hose from
the hardware store because it's considerably cheaper than sanitation hose.

I tried to caption the matter "marine sanitation hose"...

What am I missing here? ;-)

Nothing that most boat owners aren't also missing.

So, far, I am thinking even moreso that most boat owners are missing
all the benefits of simple, properly properly piped, inexpensive,
never-stinks, long-lived, easily maintained PVC.

Bonus Q for the jaded: is there a implicit, international agreement
among those plan & specify such things, that the macerator pump shall
be mysteriously concealed within an inaccesible void locatable by
occultic divination, x-ray services or systematic disassembly of the
head compartment & foreship?

No...in fact, just the opposite SHOULD be true. It--and all
seacocks--should be readily accessible for use and servicing.

I didn't realize a macerator pump was called a seacock by boating
peopleg. But I've seen a lot of USCG people call whole piping
systems & tanks things they totally aren't during compliance
inspections on larger vessels, so I'm used to it. :-)

If yours
isn't, and you left it where it was, re-read #1 above.

Mine? Not on your life. If you mean the macerator pump, it is
unreasonable to disassemble a significant portion of the guy's interior
in the middle of his season without any other cause.

ISTM you may be doing a better job of making my case (which began as a
question) than I am. I haven't noted any general advantage of this
hose product over piping.