I've had very good luck with this very simple set up shown on this and the
following page.

http://home.maine.rr.com/rlma/Strider0601.htm

No "Y" valve, no macerator pump. You have to pump by hand but, hey, we
could all use a little exercise at our age.

There is no direct overboard discharge I find pumping out the tank
occasionally less trouble than remembering to constantly switch back and
forth as we move in and out of no-discharge zones. In our home waters, we
usually have to make a special diversion to get to an area where we can
pump. Most pumping is dond at the dock.

The deck fitting seals well enough that the hand pump sucks through the "T".
When back flushing the tank with fresh water, I open the discharge pump the
hand pump a few strokes as the FW runs to clear the discharge lines.

If you have a small crew and primarily pump at the dock, this is a very
simple and workable set up.

Someone will point out the lack of a vented loop on the discharge. Save
your fingers. The through hull is only open when pumping and never needs to
be operated by a crew or guest. Even if it was left open, the water would
have to flow against two one way valves in the pump, fill the tank, and then
flow against the joker valve. It might sink the boat after a few weeks at
the dock but it's on the leaving boat checklist. Not having to pump
through the longer pipe or having a siphon break to leak odors from a dirtly
line makes the very slight risk worthwhile. If I ever need a survey for
insurance, I'm sure I'll have a fight with the surveyor though.

"krj" wrote in message
...
Peggy,
I am re-plumbing my holding tank to include a macerator pump, Y-valve, and
through hull. The easiest way to mount the macerator pump is to screw it
into the outlet of the tank then plumb to the y-valve. Question is, will
the pump out be able to suck through the pump or can I turn the pump on
while pumping out the tank. Also is there any problem with pushing stuff
through the Y-valve rather than pulling through the valve.
Thanks
krj