Steve Lusardi wrote:
I am installing a central grey water tank for sink and shower drainage in my
sailboat. The galley sink also has a garbage disposal.

The garbage disposal is gonna create all kinds of problems for
you...'cuz while gray WATER (galley, bath and shower water) can be
legally be discharged directly overboard in all coastal waters (except
in some areas of the FL Keys National Marine Sanctuary), galley WASTE
may not be. So if galley waste goes into your gray water tank via a
garbage disposal, you won't be able to dump the tank inside the "3 mile
limit" in any country that has similar restrictions...only at sea beyond
3 miles.

I've never actually examined the output from a garbage disposal to see
how finely it grinds up waste, but no matter how fine it is, bits of
food aren't gonna dissolve anywhere near as quickly as toilet waste, so
any pump you install is likely to become clogged, whether it's an
impeller or a diaphragm. Megayachts often have disposals, but they also
have very sophisticated waste treatment systems that include filters
(that must be cleaned regularly) to keep stuff out of the pumps.

So IMO, you'd be wise to reconsider having a disposal...it's gonna cause
you many more problems than it will solve.

And btw, a gray water tank produces the same odor control issues as
waste tanks, and need to be similarly maintained. Depending on the size
of your gray water AND waste tanks, you might want to consider
installing an aeration system in 'em.

Peggie
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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://www.seaworthy.com/html/get_ri...oat_odors.html