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In & Out, Same Hole - Holding Tank

Discussion in 'Ask All Sailors' started by H3newdog, May 14, 2018. Add this thread to a FAQ

  1. H3newdog

    H3newdog

    Joined Jun 23, 2015
    107 posts, 2 likes
    Hunter H34
    US Deltaville
    Okay, re-piping head with new holding tank. The new tank is 2' taller so the top "inlet" fitting is now higher. One rule of being a plumber, at least on land, is that "stuff" doesn't go up hill. The discharge connection on the head pump is lower than the inlet to the holding tank so I was wondering if connecting the head to a T at the lower fitting would work.
    In theory with the pump out cap in place the head will pump into the tank. Then when it gets pumped out the head pump (PHEII manual pump in down position) would act as a closed valve.
    As usual any thoughts greatly appreciated.
    Oh by the way it just goes against the grain with me to have the pipe to the tank going up hill.
    Also the new tank, stock, only has a 1/2" vent so all plans to follow Peggy's recommendation of 1" vent are out unless I can use the top 1 1/2" fitting for a vent. Oh yeah!
     


  2. Ron20324

    Ron20324

    Joined Jan 22, 2008
    6,022 posts, 502 likes
    Beneteau 323
    US Annapolis MD
    Probably every boat is plumbed like yours for a reason. Uphill to the tank and the gook falls into the tank. That's why heads have pumps, to move the sewage. (At home, you do not pump the sewage, it drains downhill.) Some tanks have no fittings on the bottom so they don't spring a leak and dump all that sewage into the boat.
     


  3. dlochner

    dlochner

    Joined Jan 11, 2014
    1,888 posts, 626 likes
    Sabre 362
    US Fair Haven, NY
    If the head pumps to the bottom of the tank, as the tank gets fuller, there will be more pressure on the hose and inlet, meaning you'll need a bigger pump to pump that stuff into the tank. As the level rises there will be back flow pressure on the inlet hose which will lead back to the head. A failed joker valve will let all that stuff bubble back up through the head and into the bilge. Ugly. :(

    One goal of good boat plumbing is to limit the amount of stuff that sits in the hoses. Eventually the hose permeates and the boat stinks. An alternative is to use a dipstick and pump out through the top of the tank. It is a major odor reducer. http://www.sv-secondstar.net/projects/12-holding-tank-upgrade
     


  4. Peggie Hall HeadMistress

    Peggie Hall HeadMistress

    Joined Dec 2, 1997
    6,718 posts, 444 likes
    - -
    US LIttle Rock
    First rule of marine sanitation plumbing: forget what you know about plumbing on land because a) toilets on land flush via gravity...they don't have pumps to push bowl contents to their destination (tank, treatment device or thru-hull). Marine toilets do...and b) on land the toilet is just an appliance...on a boat every piece of equipment including the toilet and the tank is just one component in a system, and anything you do to one component impacts the entire system.

    You cannot use the same tank fitting for the both the inlet and the discharge for the reasons dlochner gave you....the inlet has to be on the top and the tank must discharge from the bottom, either through a fitting at the bottom of the tank or pickup tube inside the tank if the discharge fitting on the top of the tank. You'll also have to learn to use the dry mode on your toilet to make sure that 99% of the flush actually makes it into the tank, because the pump won't prevent what's left in the toilet discharge line from running back into the bowl. The joker valve in the toilet discharge will block it ONLY until it becomes a little worn with use.

    Thanks to li'l gadget called the Uniseal UNISEAL you CAN have a 1" vent. Use a threaded plug well wrapped in Teflon tape to seal the existing vent fitting. Plan B if you don't mind waiting a couple of weeks to install a new tank would be to return your off-the shelf stock tank and order one from Ronco Plastics Ronco Plastics marine Tanks They make TOP quality thick-walled (about 3/8" which is 50% thicker than "stock" tanks) water and waste tanks for a very reasonable price and have more than 400 shapes and sizes, over 100 of which are non-rectangular, and they install fittings in the sizes and locations specified by the customer when they make the tank. You might even be able to find a tank that'll fit in a location that won't require pumping the bowl contents 2' above the toilet.
    If you don't already have my book, now would be a good time to get a copy (see link in my signature). It not only deals with odor issues, it's also a comprehensive "marine toilets and holding tanks 101" manual that will help you prevent 99% of "headaches" instead of having to cure 'em. And I'm always glad to answer any questions it doesn't, here or via PM if we need more detailed discussion than is practical in a forum

    Peggie
    "If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein
     


  5. H3newdog

    H3newdog

    Joined Jun 23, 2015
    107 posts, 2 likes
    Hunter H34
    US Deltaville
    Dlocher, I had thought about those issues. The bottom pipe is going to be filled to the tank level so I didn't think having the other pipe connected there would be any different. Due to the height differences of the holes through the framing I figure that the tank would be halfway full before it reached the same level as the head so the back pressure would not be but a few inches. Having no experience with the Joker Valve (yet) I didn't take that into consideration. I was thinking more of the pump not letting anything pass back. I so wish I had the space for connections on top of the tank instead of the side. Thanks for the link & info.
     


  6. dlochner

    dlochner

    Joined Jan 11, 2014
    1,888 posts, 626 likes
    Sabre 362
    US Fair Haven, NY
    It is probably possible to design a system to do what you initially posted, but it would be more complicated and have more potential failure points than the standard high inlet, low outlet system. To reduce the chance of back flow, the inlet hose would need to rise above the highest level of the tank and have a siphon break. The hose would also have too be routed so that a loop was always above the highest level of the tank regardless of heel angle. Then you would want a valve in the hose to positively shut off any flow while pumping out. And then there is the strength of the pump, how well can it pump uphill effectively.

    All of this is an interesting thought experiment, I'm pretty sure it is not at all practical. And the failure mode is not a mess I want to clean up.
     


  7. Peggie Hall HeadMistress

    Peggie Hall HeadMistress

    Joined Dec 2, 1997
    6,718 posts, 444 likes
    - -
    US LIttle Rock
    I'm not just pretty sure it's not practical, I'm 100% sure it would be an over-engineered disaster!
    Peggie
    "If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein
     


  8. dlochner

    dlochner

    Joined Jan 11, 2014
    1,888 posts, 626 likes
    Sabre 362
    US Fair Haven, NY
    @Peggie Hall HeadMistress You are correct, but this is what old semi-retired guys do to avoid doing the work they are getting paid to do. Just trying to follow in Rube Goldberg's footsteps. :)
     


    Last edited: May 15, 2018
  9. H3newdog

    H3newdog

    Joined Jun 23, 2015
    107 posts, 2 likes
    Hunter H34
    US Deltaville
    Thanks for all the comments. As usual I have to listen to the headmistress. The UNISEAL is interesting and I would be more inclined to use it on the top of the tank but..... as the top inlet of the old tank leaked, then someone put two screws in it to "fix" it.....I was soooooooooo disgusted with the OBVIOUS spillage, rotted floor, seat etc. not to mention the smell that I am very repeat very reluctant to use UNISEAL in the side even at the top.
    Quick some one convince me that it will work, not leak and let me increase to a 1" vent without ever leaking.
     


  10. Peggie Hall HeadMistress

    Peggie Hall HeadMistress

    Joined Dec 2, 1997
    6,718 posts, 444 likes
    - -
    US LIttle Rock
    Creating a reason for us old semi-retired gals who aren't getting paid any more for what we've done for 30 years to log onto the net every day...'cuz SOMEbody has to at least try to save you Rube Goldberg wannabes from yourselves! Or more importantly, try to save the rest of the world from you! :mad::confused::biggrin:

    I've recommended 'em for years. The Uniseal WILL NOT LEAK when sized correctly and installed correctly. Dometic/SeaLand even uses 'em in their "diptube retrofit kit." There's ONLY place I wouldn't recommend using one: to replace a waste tank discharge fitting at the bottom of a tank.
    If you'd like to brainstorm all this one-on-one in more detail than is practical in a forum, you're welcome to send me a PM that includes your email address.
    Peggie
    "If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein
     


  11. FastOlson

    FastOlson

    Joined Apr 8, 2010
    916 posts, 69 likes
    Ericson Yachts Olson 34
    US Portland OR
    The OP might want to consider a "plan b" and just have a new tank rotomolded by Ronco. Their prices are low, service and assistance is exceptional, and a new tank will probably be thicker-walled than the old factory tank.

    When we re-formatted our whole head plumbing layout, we changed to a tank with a clean-out port on top, and had all piping installed from the top. One inlet, and two outlet tubes that go to the bottom of the tank. Vent fitting was centered on top. Envisioning a boating future where more use of the HT may be mandated, we increased the capacity as well.

    This is a situation where you can make a major upgrade to your Good Old Boat that will be appreciated by your family and also by the next owner.

    I can honestly say that this upgrade was one of the major ones for gaining the Admiral's enthusiasm for cruising for a month at a time in the summers.
    When we open the hatch to go below decks there is no "boat smell."
    :)
     


  12. H3newdog

    H3newdog

    Joined Jun 23, 2015
    107 posts, 2 likes
    Hunter H34
    US Deltaville
    The reason I didn't go for a custom tank was that I found one off the shelf that would work, who knew that it would have a smaller vent hole, well maybe that they apparently sell the same tank for potable water and those only have a 1/2"!!! Well, then, there's this money thing. The custom tank price sheet shows almost twice the cost, before shipping.

    So yeah, I spent all my time after checking on the inlet and outlet sizes seeing if the taller tank would fit. So that's my excuses/reason for not verifying the vent size. But now, according to Peggy I can correct that for $1.74!!! Is that even possible? My coffee (7-11) is more than that and that leaks, well soon after...drinking it.
     



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