wrote:
A ftriend is currnently on his way from Maryland to Montreal in a, new
to him, boat, equiped with a relatively new vacuflush head. Problem
is that the head is clogged and he's trying to avoid taking the system
apart while underway to clear the clog.

It may not be clogged, it may just be a blocked tank vent that's
pressurized the tank, creating backpressure that prevents waste from
getting past the vacuum pump. So the first thing he needs to check is
the tank vent. The two most likely places for a vent blockage are the
vent thru-hull and the connection to the tank--both the fitting and that
end of the vent line. Open the deck pumpout fitting--very carefully, and
with a hose at the ready--to relieve any pressure in the tank before
removing any hoses in the system. If the tank is pressurized, it'll spew.

But before he even does that, he needs to check his owners manual...it
includes just about every possible problem, causes and cures that a
Vacuflush can develop. If he doesn't have one, he can download and print
one off the SeaLand website:
http://www.sealandtechnology.com/pdf...Flush%20OM.pdf

Given that some pump out systems use a vacum tank and develop a fair
bit of suction power is it worth it to try and clear the blockage that
way? I.e. block the tank vent and go get a pump out and hope that
this dislodges the clog. This would of course depend on being able to
equalize the relative pressure in the holding tank through the
Vacuflush head during the pump out. Is this possible?

Nope...and it can damage the system. However, if it really is a clog, a
VacuFlush is one of the few toilets on which a plunger can be used
without any damage to the toilet. If that doesn't work, I suggest he
call SeaLand for advice: 800-321-9886...'cuz blindly tackling any
problem with a VacuFlush can turn one problem into three problems.

What SeaLand won't tell him, though, is how much water a VacuFlush
REALLY needs. Their claim that the V/Flush can use "as little as" 1 pint
of flush water is VERY carefully worded. If only urine is flushed...no
water added to the bowl first, no TP either...then yes, you CAN get away
with that little, at least for a few flushes. But if you do much of
that, unless you want odor, at least once a day you need to run at least
half a bowl of clean water through it to rinse out the system. It's also
advisable to add at least half a bowl of water ahead of solids or any TP
(iow, every time a female uses the toilet)...that's a quart or more.
It's also essential to leave the pedal down for at least 7-10 seconds
after the bowl is empty to rinse out the pump and duckbills--to prevent
a buildup in the pump or bits of waste or TP from becoming stuck in a
duckbill, creating one of those pesky air leaks that causes the pump to
cycle for no reason...at least another quart. And if you don't want
permeated hoses, it's a very good idea--last thing before the boat will
sit (or at least once a week if you're living aboard)--to fill the bowl
to the rim with clean water and flush it through to thoroughly rinse out
the vacuum tank, hoses and pump...'cuz suction splatters waste all over
'em and the flush water flow isn't sufficient to completely fill the
hoses. So, averaged out over a week, the VacuFlush actually NEEDS about
the same amount of flush water that most toilets need: about .5 gal.
Using much less than that, you're asking for problems.

Btw...I had V/Flush toilets on my last two boats and was also a dealer
for nearly 10 years...so I'm INTIMATELY acquainted with 'em...what keeps
'em working trouble-free and what doesn't.

Give me another shout if I can be of further help.

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://shop.sailboatowners.com/boat_odors/