Adam wrote:
I. The idea with fresh water from sink - it's very clever but not
"understandable" for all on board.

Perhaps not for flushing, but surely you could could use it to flush
all the sea water out of the system weekly. But, it's your boat...

I have plenty of room so I'll go with separate tank.
The question about that: - how big is reasonable? I would go with 30
gallons.

"Big enough" depends on several things: how many people are using the
head, how much flush water the toilet uses, how long away from the dock
to refill it.

With separate tank I will be able to use electric or manual head.
Not for
pressurized water.

I can't find an earlier post of yours I was looking for...but didn't you
say you're installing a watermaker? If so, why the concern about
fresh water consumption by a toilet that uses pressurized water? For
that matter, if you have space for another 30 gal. tank to do nothing
but supply flush water to the toilet, why not just increase your fresh
water holding capacity instead. Toilets designed to use pressurized
flush water use half or less the amount required by raw water toilets.

But whatever you ultimately decide to do, we prob'ly ought to discuss
which toilet before you buy one.


II. Why separate tank for Gray water - if I do not have a tank I'll
have to
use two pumps; for shower and galley. With tank I can connect galley,
sink
and shower together and pump out if needed.
The concern is only if it is another source of odour problem.

It is. A gray water tank is full of bacteria, and can stink as bad as,
even worse than, a waste holding tank. Plus, gray water tanks also have
grease, soap scum, hair etc to deal with. Your galley and head sinks can
drain directly overboard...only the shower needs a sump. And a smal sump
is a LOT easier to keep clean and odor free than a tank.

Second seacock 2" is intake - for all sources including engine, ac and
fridge.

Get some advice from engine, ac and fridge mfr about the advisability of
only one common intake and the size needed. My first thought is that all
running at the same time could reduce the water flow needed by one--or
even all--enough to damage its pump.

Third 1.5" for head discharge - bellow water line

Consider adding a Lectra/San (CG Certified Type I MSD that treats waste
and discharges it overboard legally)...you'd use the holding tank only
if/when you ever visit a "no discharge" harbor.

And it looks like I'll need one more for gray water just above water
line.

If you go with a shower sump instead, you could tee it into the head
discharge line...after the Lectra/San, but ahead of the vented loop.

--
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://69.20.93.241/store/customer/p...40&cat=&page=1