On Thu, 15 May 2008 10:40:21 +0200, "Steve Lusardi"
wrote:
Bruce,
It is precisely Peggie's response that generated this query. I have spoken
to her on the phone about this issue in February. Peggie does not know one
stainless alloy from another and could not give me the precise circumstances
that created this condition, nor could she identify the alloy used. I
respect her knowledge immensely and do not doubt for a second that this
occurred and is true, but I am faced with a dilemma and need to understand
the corrosion risks better in order to mitigate those as well as possible,
hence this query. Please note Spehro's response above. It verifies my
initial response to Peggie's statement. There was something else going on.
It could be this bacteria thing, but my best guess at the moment is
stagnation, free oxygen deprivation and the resultant crevice corrosion was
the culprit. In addition to this query, I sent a similar one to the valve
manufacturer, but I have not yet received the response. Right now it looks
like my solution to the dilemma is to double valve the holding tank exit
line, first with plastic and secondly with 316L at the hull.
Steve
It sounds to me as though you have an installation with a holding tank
and a thruhull pump out in a steel boat. If that is the situation I'd
plumb the thruhull with the hull/seawater in mind as the fittings will
have limited contact with sewage... assuming that you flush the lines
after pump out, and use plastic for the tank plumbing.
Even if you have a bowl to thruhull system, without a holding tank,
there is still limited contact of concentrated sewage with the
thruhull as you initially pump water and then when it is flushed
clean you usually flip the lever and pump until you have blown the
lines clear of liquid. Of course, there is some leakage back through
the joker valve so sea water seeps back but I'd guess that the
majority of the liquid in contact with the thruhull is going to be sea
water.
I'd guess that the other fellow's recommendation of 316L is probably
your best choice.
"Bruce in Bangkok" wrote in message
.. .
On Wed, 14 May 2008 17:47:45 +0200, "Steve Lusardi"
wrote:
Will urine ie human waste corrode 316L valves and pipe? The question is
asked because waste tanks are typically plastic, but Lloyds A1
certification
requires all through hull valves to be fire proof. Fireproof valves are
typically 316L. I have purchased all my valves from the chemical industry.
I
have been told that urine will corrode 316 over time. I don't believe it.
If
316 is good enough for corrosives in industry, why would it not stand up
to
human waste? If anybody knows for sure, please let me know.
Steve
There was a thread on rec.boats.cruising today in which a lady named
Peggie Hall states:
----------------------------------------------------------------------------------------------------------
SS fittings in the sanitation system plumbing??? Not a good choice,
'cuz urine will corrode 'em. At least one trawler mfr who puts all
fittings on the top of the tank, with a pickup tube inside the tank on
the discharge (a great idea) used stainless fittings and pickup
tubes--a
VERY bad idea, 'cuz the tubes are corroding, even falling off in
pieces
inside the tank, in just a few years.
--
Peggie
----------
Peggie Hall
Specializing in marine sanitation since 1987
Author "Get Rid of Boat Odors - A Guide To Marine Sanitation Systems
and
Other Sources of Aggravation and Odor"
http://shop.sailboatowners.com/boat_odors/
---------------------------------------------------------------------------------------------------------
Peggie has been posting on rbc for some years now and her posts have
always been logical and informative.
You might try contacting her for additional information.
Bruce-in-Bangkok
(correct Address is bpaige125atgmaildotcom)
Bruce-in-Bangkok
(correct Address is bpaige125atgmaildotcom)