How large a boat for a second head?

It depends on the type of sailing you do, the number
of people on the boat, and sea conditions.

If all you do is day sail, you don't need any head. However
if there is space, a single head is a nice option.

The number of people on a boat make a second head
on a boat a valid consideration. Sometimes you need
to use the head in a hurry, and can't wait. Some people
dive overboard to do it in the water when they can't wait.
That is not always possible.

Second heads have the advantage you can designate one
head for guests and one for yourself. If people are slobs
about keeping the head clean--and that happens often, they
suffer for it, not you. Many times I think people avoid
keeping the head clean because, in that confined space
people tend to become nauseous, and turn away rather than
keep it clean. If it's your boat, you probably don't want
to clean up other people's messes, and it's easier to hose the
head down back at the dock and letting it air dry.

A second head also makes a good hanging wet locker.
I've used second heads--forward heads, for sail and anchor
storage on longer trips.

Rough weather ocean sailing changes everything on a boat.
You have to think about how things will function when
everyone is seasick to one degree or another. In the worst
of conditions, standing up down below means instant nausea,
with vomiting to follow minutes later. Having a head near
each stateroom makes a huge difference to someone who feels
deathly ill and wants to take as few steps as possible to the
head, and return to their bunks to lay down to recover. It
means the difference between nausea and vomiting. Rapid
fluid loss is no joke, and has a compounding effect on the
human body. A second head, or third head, helps prevent
vomiting. It keeps your crew more functional and helps them
recover more quickly.

I agree with katy, a head should be close to the companionway,
particularly when it is the only head on the boat. Many times
I've quickly turned out for my watch, done my business in the
head, and scrambled into my foulies on deck, in a few short
minutes, to find the relief of the fresh air and avoided turning
nausea into vomiting. Taking extra steps towards the front of
the boat, where it is rougher? Unthinkable! I'd rather go straight
on deck, refresh myself in clean air, and use a bucket or the back
rail.

Many people hide in their bunks in these conditions. More
experienced sailors don't let their crewmates down. They use the
head to vomit, feel better for it, and go out on deck to stand their
watch no matter how bad they feel. I recover more quickly this
way. If I had to point to any one thing that make a good sailor,
it is how they deal with seasickness. In these conditions it is still
easier on yourself or your crew if fewer steps are needed.

Having a head close to the companionway makes perfect sense in
rough conditions. Having extra heads on board is the smart for
ocean sailing boats, or if you want to avoid cleaning up after
someone else.

Bart Senior

Thom Stewart wrote
Question; no points?

Just how large should a Vessel
be to give up the space to a second head?

Katy talked about Treking thru the boat to the head in the fore area. On
my boat the head is at the Companion Way. I'm never more than 10 ft
away. I don't consider that a Trek.