Boat Waste Tank Gauge

Discussion in 'Boat Design' started by rasorinc, Jun 13, 2015.

  1. rasorinc
    Joined: Nov 2007
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    rasorinc Senior Member

    Does anyone know of a quality and accurate gauge for a boat 75 gal. waste tank? Lots of water measuring gauges but few that spell out measuring waste.
    I would really feel better with a personal recommendation. Thanks much.
     
  2. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    Google " rv holding tank sensors "
     
  3. AndySGray
    Joined: Jun 2014
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    AndySGray Senior Member

    Yes, this is not a job where re-purposing a fuel sender will work.

    The common off the shelf solution involves a sealed tube with magnetic reed switches inside, a doughnut shaped float goes over the tube (with a flange at the bottom to stop it falling off).

    The float has magnets and will switch the low medium and full switches as it rises.

    The downside is you can't use just any standard gauge and is not as accurate, but it is sealed.

    Some tank materials will allow a series of ultrasonic sensors to be glued to the outside that go from open to closed as liquid becomes present at the other side.
     
  4. Rurudyne
    Joined: Mar 2014
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    Rurudyne Senior Member

    Totally random thought: there is air in the tank, right? Because of the vent this air may not be the same temperature as the fresh poop or pee. In fact a fresh one will be warm.

    In another thread hereabouts people were discussing the use of IR technology to look inside structures. How about using a system that is keyed to the use of the toilet. This would permit two strategies. First the sensor could locate the level the more recent addition settles at and second whatever temperature difference there may be between the air and the ... stuff ... may show up. Between them the sensor could keep track of the level and intermittent use would help to keep electricity use down.

    Could be salable to early adopters who who want to keep up with the latest ... stuff.
     
  5. cmckesson
    Joined: Jun 2008
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    cmckesson Naval Architect

    My personal solution is a sight glass. Nearly infallible: It does get plugged with poop at the bottom, so I have a routine of periodically taking the dinghy inflation pump and pumping air down the sight glass from above to blow it clear.
     
  6. CDK
    Joined: Aug 2007
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    CDK retired engineer

    Even the number one portable toilet maker Thetford doesn't offer more than a simple float switch and a red LED warning light telling the user the tank is full to the brim.

    RVs and caravans employ a simple current measuring circuit in the "gray water" tank, with 4 stainless screws in the tank's wall and a 4 stage display. It works only when the tank is new or recently cleaned.

    If you really want an accurate indication, use a vertical plastic tube, protruding above the top of the tank and connected to a pressure transducer or a mechanical pressure gauge. The pressure of the air column in the tube indicates the fluid level.
     
  7. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    All the gauges that use electric die in the tank.

    This is a remote reading unit that can measure ALL your tanks , waste , water , fuel , what ever you need.

    Should it plug up all that is required is a bit of air pressure to clear it.

    tanktender.com/
    An introduction and summary of the benefits of a Tank Tender by Hart Systems.
    Hart Systems - About Tank Tender
    tanktender.com/about.html
    An introduction and summary of the benefits of a Tank Tender by Hart Systems.
     
  8. Joakim
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    Joakim Senior Member

  9. AndySGray
    Joined: Jun 2014
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    AndySGray Senior Member

    A common industrial solution, where there is a requirement for nothing inside the tanks, is weight.

    75 gallons will weigh about 625 pounds

    The tank does need it's own structural integrity as it supported on four points (corners).

    Using a couple of blocks at one side and a pair of e.g 200 pound load cells at the other would give a very accurate weight allowing the used capacity to be shown.

    These are getting quite cheap and a pair of load cells plus the electronics can be had for under 100 bucks

    :D
     
  10. steve123
    Joined: Dec 2014
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    Location: China

    steve123 Junior Member

    Fitted over a hundred SEALAND TANK WATCH never been any problems.
     

  11. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    In terms of water efficiency nothing beats an RV toilet .

    Of course it must be mounted directly on top of the holding tank.

    NA hate that restriction as much as they hate servicable fuel tanks , instead of boxes for fuel

    If its a new build use the RV system , no gauge required , you simply look in from above.
     
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