I have a Traveler toilet that sits right on top of a 90 gallon holding
tank. The toilet dumps directly with gravity and works great. The tank
can be emptied with a standard pump-out fitting or I have an electric
pump that I can use to empty the tank directly overboard which of
course I only do if I am offshore where it is legal. The electric pump
pumps from the top of tank with a dip tube to the bottom. The direct
discharge pump and the pump-out set up use separate piping.

I have tried two different pumps both diaphragm types designed to pump
unmacerated waste. The first pump was a Whale and the second is a
Johnson. The problem is the pumps don't prime if even the slightest
piece of crap has gotten into the flapper valves. The two pumps have
differently designed valves but the principle is the same. I
understand that the tank should be completely pumped out and then
rinsed with water so theoretically the pump is cleaned and ready for
the next time but that only seems to work in theory. I am very tired
of taking the pump apart and cleaning the valves every time I want to
use it.

Would I be better off with a macerator pump?

No, that Whale pump is about the best you can get. I check for vacuum
leaks between the tank and the pump. With all the flapper valves in
the Whale, it's hard to imagine them failing all at once. Are you
using cheap, single ply toilet paper in there? Also make sure nobody
is throwing anything else down there. If the valves are indeed being
held open, it's by something that shouldn't be in the tank to begin
with. Whatever that is would crud up a macerator as well.

gaffcat wrote:
I have a Traveler toilet that sits right on top of a 90 gallon holding
tank. The toilet dumps directly with gravity and works great. The tank
can be emptied with a standard pump-out fitting or I have an electric
pump that I can use to empty the tank directly overboard which of
course I only do if I am offshore where it is legal. The electric pump
pumps from the top of tank with a dip tube to the bottom. The direct
discharge pump and the pump-out set up use separate piping.

You aren't gonna enjoy checking this out...but I suspect that either the
end of pickup tube is cut flat instead of at an angle and is also too
close to the bottom of the tank or the accumulation of sludge in the
bottom of the tank has gotten so deep it's clogging up the pickup
tube...or both.

It's not THAT hard to flush out a tank....in fact, since you have two
separate discharge fittings, it's actually very easy and can even be
done at sea if you have a washdown pump.

It's not necessary to fill the tank...you only need enough water to stir
up the sludge enough to put in suspension so it can be pumped out.
Stick the washdown hose into the deck fitting...start the overboard
pump...and just keep the water flowing till what's coming out the
discharge is clean water. Voila...both the tank and the pump are clean.
You don't have to do it every time you dump the tank...2-3 x a season is
enough to keep the sludge level down.


Would I be better off with a macerator pump?

You'll have problems with any pump if the end of the pickup tube is
buried in sludge.



--
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/books...ku=90&cat=1304

Thank you Peggy and Keith,

I have the toilet removed so I have a larger hole for access. I have
been trying to get the sludge to break up. I have pumped a lot of
water into and out of the tank but quite a bit of sludge still
remains. I'll keep trying.

A note to builders: Do not position your washdown raw water intake
seacock close to your holding tank discharge seacock.

I am trying to convince myself to cut off the waste pump holding tank
diptube inside the tank to shorten it. I would be able to barely reach
it inside the tank through the toilet hole. I think it is now about 1"
above the bottom of the tank. Should it be maybe 2"? The tank is
plywood/epoxy/glass and the diptube is glued in PVC.

I had been using some enzyme based additives to try and break up the
sludge, including the KO brand. Perhaps I should have been using it
from the very first when the tank started seeing use about a year ago
but it doesn't seem to do much now. The tank has a 1 1/2" vent.

One thing I did do last night was to plumb in a connection to the
waste pump suction line from the washdown system. Using a Y valve I
can send raw water directly through the pump to rinse it out, it seems
to work great.

gaffcat wrote:

A note to builders: Do not position your washdown raw water intake
seacock close to your holding tank discharge seacock.

Or at least put it forward of the tank discharge. Same goes for toilet
intake thru-hull, btw

I am trying to convince myself to cut off the waste pump holding tank
diptube inside the tank to shorten it.

You don't want to do that. It should be about 3/4" off the bottom, cut
at a about 25 degree angle. Any shorter leaves too much in the tank. Cut
flat instead of at an angle and any undissolved TP or sludge can clog it.

I had been using some enzyme based additives to try and break up the
sludge, including the KO brand.

If you've used K.O. (which, btw, is live bacteria, not just
enzymes...enzymes alone are practically useless) according to
directions--which include flushing out the tank regularly--it's unlikely
your clog is sludge. If you've only used it to try to break up the clog,
you may not have used enough or may not have given it enough time to
work. It'll take a lot more of it to dissolve a sludge clog than for
regular tank maintenance...and it takes time to work--at least 48 hours.

Perhaps I should have been using it
from the very first when the tank started seeing use about a year ago
but it doesn't seem to do much now. The tank has a 1 1/2" vent.

Off the wall thought: have you checked your tank vent for a blockage?
'Cuz if the vent is blocked, it'll create a vacuum that'll definitely
prevent the pumpout from pulling more than about a gallon out, and could
prevent the tank from draining...like when you hold your finger over the
end of a straw in a glass of water and take the straw out of the water,
the water stays in the straw till you remove your finger so that air can
get into it to replace the water draining out. However, if you're able
to pump out, a blocked vent is unlikely. Still worth checking,
though...the two most common places for a vent blockage to occur are the
vent thru-hull and the connection to the tank--both the fitting and that
end of the vent line.

One thing I did do last night was to plumb in a connection to the
waste pump suction line from the washdown system. Using a Y valve I
can send raw water directly through the pump to rinse it out, it seems
to work great.

If it can generate enough pressure, you may be able to break up whatever
is clogging the line.

--
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/books...ku=90&cat=1304