Speaking of vents::

If your going to combine any vent lines, be sure you they won't create a
syphon between port and stbd tanks while healed over.

What I did to over come this problem, was to locate each vent fitting at the
outboard edge of the tank top. That way the higher tank will always have the
vent fitting in the resulting air pocket while, even though the low tank
vent might have water up to it, the opposite tank will still be higher due
to the boats heal angle. This wouldn't work if the vents were vented at or
near the centerline.

All of my tanks are at a equal tank top height, fore and aft, port and stbd
while the boat is on an even keel.

I run my combine water vent to the shower stall.

Another feature, I'm working on. The water heater is in the engine
compartment, about 20 ft from the head and shower. I am putting a valve in
the hot water line, near the head sink, that will divert this water back to
the freshwater manifold until hot water is up to the fixture. This may seem
'anal' but it will save a lot of wasted water while waiting for the warm
stuff.

However, speaking of combine vent:: I did end up with a problem of cross
over between my holding tank and my gray water tank. They share the same
vent and even though they are tee'd to gather about 3 ft above the tanks,
when ever the holding tank is full (I don't have gage) the liquid flows over
into the gray water tank. Eventually I will discover the problem when the
gray water backs up into the ice box drain. YuK.

Well, that's my take and experience on the tank plumbing situation.
Live(aboard) and learn from your mistakes. FWIW.

Steve
s/v Good Intentions

Steve wrote:
Speaking of vents::
However, speaking of combine vent:: I did end up with a problem of cross
over between my holding tank and my gray water tank. They share the same
vent and even though they are tee'd to gather about 3 ft above the tanks,
when ever the holding tank is full (I don't have gage) the liquid flows over
into the gray water tank. Eventually I will discover the problem when the
gray water backs up into the ice box drain. YuK.

You're gonna have worse problems than that, Steve. Waste contains animal
fats and other stuff that's building up in your vent. It's prob'ly
already reduced the diameter at the tank fitting and tee considerably,
and will completely block the vent. But you won't know it till both your
waste and gray water tanks either become pressurized or you can't dump
'em at sea because of the vacuum...or worse yet, a strong pumpout cracks
one or both 'em.

I'm surprised you can tolerate the odor that has to come out the vent
each time the head is flushed or anything goes down a drain.

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

However, speaking of combine vent:: I did end up with a problem of cross
over between my holding tank and my gray water tank. They share the same
vent and even though they are tee'd to gather about 3 ft above the tanks,
when ever the holding tank is full (I don't have gage) the liquid
flows over
into the gray water tank. Eventually I will discover the problem when the
gray water backs up into the ice box drain. YuK.

You're gonna have worse problems than that, Steve. There are animals
fats and other stuff in waste that are building up in your vent
line...they've prob'ly already reduced the diameter significantly and
will clog it. But you won't know it till both your gray water and waste
tanks have become pressurized...or you can't dump either one at sea
because of the vacuum created...or worse yet, a particularly strong
pumpout implodes a tank.

I'd also very surprised if whatever gasses are forced out your vent
aren't noxious enough to knock out any birds or insects within 50' of
your boat!

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