Boat: Warrior 35 Mk III
worldwide are tightening up regarding discharge of "black water" toilet
waste and crowded moorings/anchorages/marinas result in the
undesirability of pumping "unsociable" waste into the surrounding
galvanised me into fitting a holding tank into my Warrior.
Having mulled over possible tank sizes and locations for some time, I
have decided to go down the "smaller capacity, low cost, practicality of
fitting, and minimum disruption to existing head" installation route.
used a Vetus 42L "Black Water" Tank.
Dimensions L x
W x H (mm):: 460 x 350 x 290
This is the largest that I could fit in the heads locker beneath the
standard Warrior moulding sink top (and forward of my homemade GRP sink)
It lies against
the curved hull and therefore at an angle, with the lower right hand
edge of the tank (nearest to camera) supported by a bracket (hidden from
view) bolted to the fascia just forward of the locker doors. It's close
to the underside of the locker roof and against the forward bulkhead
with appropriate anti-chafe measures.
It may appear to be an unorthodox fitting, but it is secure and has
advantages being at an angle. The outlet is at the lowest part of the
tank and inlet at the highest, to maximise useful capacity. Note that
only the two white pipes are part of the holding tank installation.
There is additionally a 12mm vent pipe (90° fitting) in the top surface
of the tank and as close to the highest edge as possible, which runs
forward to the bulkhead and then bends upward through a hole to the
inner forward corner of the right hand locker above the sink (the
junction of the locker front and forward bulkhead). From there it runs
thwart ships, out toward the hull alongside the bulkhead to a skin
fitting just below the hull/deck joint (photo to come).
tank inlet and outlet pipes both exit the under sink locker at the
bottom to meet the 2 diverter valves beside the head bowl. Because of
the restricted space, it took some experimentation (and a hot air gun!)
to establish a physical pipe arrangement to connect everything together
and to the Simpson Lawrence SL401 toilet.
The Y valves in
the photo below are shown in the tank bypass position ..... where the
toilet pumps to
which discharges out through existing hull skin fitting.
When the lower
valve is turned 120° clockwise,
is closed off and the toilet pumps into the tank (A
When the upper valve is turned 120° anti-clockwise, the tank drains (D
is closed off.
both valves set like this, flushing the head pumps water into the tank
which immediately drains back out .....useful for helping to flush the
There are two
clever aspects of this arrangement:
tank outlet just happens to be at sea level, the tank will
continually partially back-fill and empty when sailing or even when
motoring in choppy conditions, therefore automatically helping to
flush the tank. In fact, when beating hard from one tack to the
other, the tank will completely fill on a starboard tack and empty
at a faster rate than normal on port, due to the increased height
above sea level. This is a useful way of keeping the tank sweet and
clear of paper blockages.
If the tanks
outlet does become blocked, the valve arrangement allows you to back
flush the tank using the toilet, which should move the blockage,
hopefully allowing it to empty normally afterwards.
To do this, shut off the hull outlet sea cock, set the lower valve
in the fully anticlockwise position ( as when flushing directly to
sea) and set the upper valve into the halfway position. This half
open position allows water to follow a
through the valve coming from the toilet
The Vetus tank
comes with a 3" white screw plug which being accessible on the side (
see photo) would also allow a certain amount of poking around with a
bent stiff wire to clear a hard paper blockage (if only partially full).
I have had no
blockages or problems with this system since installing it in May, and I
do pass toilet paper through it. I am aware of other yachts having had
trouble with toilet paper blocking the outlet, so time will tell. I do
follow the principal of partially flushing the tank when I can and not
leaving it absolutely empty when not aboard for a time. This should
avoid any remnant paper sheets from drying out.
Rather than add
the expense and bulk of a no-smell filter, I have fitted a cheap plastic
in-line tap. As much of the time the holding tank is by-passed, leaving
this closed prevents whiffs emanating from the tank.
Note that you
may wish to include a valve that closes when the tank is full to avoid
liquid pumping out of the air vent.