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holding tank - no macerator on overboard discharge

Discussion in 'Post Yacht' started by incoming, May 3, 2024.

  1. incoming

    incoming Member

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    The holding tank on my post 42' has no macerator on its overboard discharge.

    Does anyone know if that's typical in this installation?

    Also, the holding tank is below the galley sole. Which, I think, means it is (at least partially) below the water line. So wouldn't opening up the discharge sea cock just fill up the tank with sea water, given there is no macerator to pump the "stuff" overboard and keep the sea water from flowing in?

    The seacock is currently stuck shut, and i'm trying to decide if its worth trying to free it up or if its not worth dealing with unless i install a macerator as well.

    Any post owners that have this same set up? Does it work? Or does it seem likely the macerator may have previously been there but removed.
  2. Capt Ralph

    Capt Ralph Senior Member

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    You still on the hill? Now is/was the time to check that sea cock.
    The head grinds stuff up pretty well, it is just liquid (thick) in the tank.
    I think It is just above above the water line. I think gravity is your friend.
    I'll double check my pictures tonight.
    Just taking a break on Bertie while installing the new laundry machines.
    These have been sitting in the car port since November..
  3. incoming

    incoming Member

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    I may have missed my chance. I called down to the yard and its going back into the water right now
  4. Capt Ralph

    Capt Ralph Senior Member

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    Call back and ask them to work those sea cock before splashing.
    Or else, they should not be leaned on till next haul.
  5. Capt Ralph

    Capt Ralph Senior Member

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    Nothing in my pictures.
    My pictures do not include the starboard end of the black water tank.
    Viewable under the last deck plate aft, center-line, by the galley.
    I do not recall anything there or I would have a picture of it.

    I found my notes. No black pump mentioned here either. Just the sea-cocks and hoses.

    I do think it is a gravity drained tank. Straight down thru that 1 1/2" sea-cock, that was stuck closed.
    20240313_094243a.jpg
    Last edited: May 3, 2024
  6. incoming

    incoming Member

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    Here’s a pic

    Attached Files:

  7. Capt Ralph

    Capt Ralph Senior Member

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    Uh Oh,,,, That is not white hose going to that sea cock.
    I missed that.
    Where The Frack* does that bottom white hose go??
    Please forgive me brother, I may have messed up.

    *Another WTF episode...
  8. porthole

    porthole Member

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    What year is the boat? My 42 was a 1980 and had no tank, just a non functioning LectraSan.
    I did add a tank and macerator along with some other changes to the head system.
  9. incoming

    incoming Member

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    the bottom white hose goes to the stuck seacock, which is forward of the companionway stairs under the floor, near where the seacocks are for the overboard flush and raw water head intake. Same seacock I believe your photo is of

    the picture was taken from inside the closet under the TV, with the access panel removed on the wall looking toward the port

    the boat is a 2000
  10. ranger58sb

    ranger58sb Senior member

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    I see there's been some discussion here already, but...

    Do you mean there's no pump at all on the overboard discharge line? Or do you mean the pump isn't the macerating kind?

    Yes, holding tanks below the waterline can backfill of the seacock is left open.

    FWIW, we are "inland" almost 99% of the time, so wouldn't necessarily rush to fix the seacock and deal with a pump issue. I'd do it, 'cause "everything on the boat must function properly" -- but not necessarily at highest priority. OTOH, where you are, presumably potential for off-shore dumping, I'd probably prioritize higher on the list...

    -Chris
  11. incoming

    incoming Member

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    There is no pump at all. The tank discharge line runs directly from the tank to the seacock.

    we do tend to fish and do offshore cruising, and the tankage on the boat is somewhat small for 4 people (which is what we usually have), so overboard dump is a nice to have but not essential as we also have a pump out right at our slip. It may need to wait until next haul out, which I’m sure will be sooner than I want it to be.

    The yard manager was the one trying to convince me it’s not worth trying to free the sea cock due to the set up with out an overboard pump/macerator.
  12. Pascal

    Pascal Senior Member

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    Personally I prefer the black water discharge to be above the waterline as that means one fewer seacock to worry about…. And you can easily add the thru hull while on water.
  13. Capt Ralph

    Capt Ralph Senior Member

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    I recall Incoming mentioning a new head maybe in his the future.
    When this this happens, may I recommend a whole new MSD system.
    MSD1; Automatic treatment and overboard discharge.
    Raritan's later heads and treatment systems now work together, push one button; everything is flushed, treated and pumped away.

    Josie, her son and myself lived on Bert our for many years with slip side pump out.
    Some times it was close but we used a single, scheduled, weekly pump out.
    Then we installed a Purasan system on our Bert a few years ago. MSD1
    Works great with our old Crown (master stateroom) head.
    When in the KEYS, a zero discharge area, I can still switch to holding tanks. MSD3
    The forward heads are rarely used anymore, they stay MSD3

    I also learned to preferred below the water line pump over options. Less odors in the air.
  14. ranger58sb

    ranger58sb Senior member

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    When we replaced our holding tank and related plumbing on our previous boat, we changed to top-mounted (dip-tube) hoses for everything, one to the deck plate, another to a (new) macerating overboard discharge pump, one for "input," and one for the vent hose. Plus an access plate for the tank level gauge. The overhead approach effectively increased our capacity, compared to the previous side-mounted fittings. It happens we were able to use a taller tank than the original, and that increased our capacity too.

    Separating the routing to deck plate and overboard was useful, partly to simplify routing to deck plate (one direction) and overboard pump (different direction). It also meant there wasn't so much "standing effluent" in the hose that went to the overboard discharge pump. Hardly any, in fact. Intention was to be able to clean/service/replace the pump any time without so much goo to deal with.

    -Chris
  15. Greg Page

    Greg Page Senior Member

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    It is like our 43. Holding tank overboard discharge is gravity. Can only use when boat is moving forward. Yes, it will fill the holding tank if open when stopped.

    I have them service mine every haul out. PO just left closed for years so hose 'gelled' solid. A ***** to have them replace hose (and sea cock) and quite pricey.
  16. incoming

    incoming Member

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    The hose is now new - but unfortunately the seacock still stuck closed. I could put my pvc pipe “breaker bar” on the handle and give it a tug…or just wait until next haul out
  17. Capt Ralph

    Capt Ralph Senior Member

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    Did it move at all for the surveyor? Any?
    I did not try it at all knowing you were going to pull soon.
    It looks like a big sea-cock. it may take some tension and move or,,,

    But, I know what your thinking,,,
    Naw, I don't have a 44 mag anymore,
    But your next thought, If I just gave it a try,,,,....
    Sometime things just start working.

    Remember; Murphy lives and waits with Mayhem in bilges like this.

    It should have just an open fitting on the outside of the hull.
    Have a selection of tapered wood plugs ready and be ready for a swim before you start putting a pipe wrench to it.

    Yep, I have witnessed when such things go wrong. While working for SeaTow and our own company.
    Jumped in with a towel or rag before.

    That's why I tell folks to work on their sea-cocks while on the hill.
    Gee, where have you heard that before..
    Luv ya brother but I got to rub it in now. :):)
  18. Pascal

    Pascal Senior Member

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    Since you can only discharge overboard while offshore, you won’t get any smell underway…
  19. Capt J

    Capt J Senior Member

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    The way the old posts were set up was it gravity discharged while you were on plane. It had a backwards clamshell and running on plane it would simply drain out the bottom when you had the seacock open. I worked on a 50' that had that, as well as a macerator pump too and another seacock.
  20. Greg Page

    Greg Page Senior Member

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    I knew I had seen the holding tank empty procedure somewhere. It is on page II-26 of the 42 Post owners manual. PM me if you want an electronic copy.

    Post 42 Manual Page II-26.jpg