Peggie,
As I mentioned before, bronze is absolutely out of the question with a steel
hull. They create a huge electrolysis issue which causes both valve failure
and steel corrosion throughout the hull. I think using plastic within the
sanitary system and 316 at the hull is the best compromise. The reasoning is
that the stainless will be continuously flushed with seawater and only
sometimes exposed to waste. The valve which will be continuously exposed to
waste will be plastic.
Steve

"Peggie Hall" wrote in message
...
Steve Lusardi wrote:
Peggie,
The dilemma is the Lloyds certification for thru hull fittings, which
call for fire proof valves against your years of experience.

If you must use metal for your thru-hulls, use bronze. It's a lot more
resistant to urine than SS...almost bullet proof. In fact, the best
high-end manual marine toilets--Blake, W-C Skipper, Groco K etc--are
bronze "thrones."

--
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/