Blackwater and Greywater ...seperate?

Discussion in 'Boat Design' started by Mick@itc, Jan 27, 2011.

  1. Mick@itc
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    Mick@itc Junior Member

    Hi
    I am relatively new to various systems aboard and one that currently puzzels me is the Blackwater/Greywater differenciation. From a landlubbers viewpoint the Black and Grey generally get mixed together to go to the sewerage plant.
    On boats it seems to be different...Can someone please check my understanding of the Black and Grey water systems for accuracy...

    First of all the Black water...
    - Has sources only at the toilets in the boat;
    - Usually has a macerator between the bowl and the blackwater holding tank/outlet;
    - Has a pump (manually or electric) between the bowl and the holding tank/outlet;
    - Usually has a holding tank so that stuff is not poured out in restricted zones...i.e. marine parks, inland waterways etc;
    - Usually has a direct to sea outlet for pumping out to the sea in unrestricted zones;
    - Has some form of (electrically operated?) valve that changes flow between direct to sea and into holding tanks;
    - Has a pump that pumps from the Holding tank to the sea;

    Second grey water...
    - Has sources from the showers, handbasins, sinks, appliences (washing machines, dishwashers, etc) in the boat;
    - Usually has a macerator between the sink and the greywater holding tank/outlet;
    - Has a pump (manually or electric) between the showers/basins and the greywater holding tank/outlet;
    - Usually has a holding tank so that stuff is not poured out in restricted zones...i.e. marine parks, inland waterways etc;
    - Usually has a direct to sea outlet for pumping out to the sea in unrestricted zones;
    - Has some form of (electrically operated?) valve that changes flow between direct to sea and into holding tanks;
    - Has a pump that pumps from the Holding tank to the sea;

    These are two seperate systems, correct???

    Looking forward to feedback.

    Regards
    Mick
     
  2. Ad Hoc
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    Ad Hoc Naval Architect

    Correct.
     
  3. rwatson
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    rwatson Senior Member

    Interesting - is this a practicality based design, or a legal requirement, or both ?
     
  4. keysdisease
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    keysdisease Senior Member

    Depending on the size of the vessel, both.

    In many places there are discharge laws for black water, these range from various levels of treatment before discharge to no discharge of black water at all. For grey water in many places there are little to no restrictions .

    On a small boat the sinks will often just drain overboard and the heads will either flow to a tank or an on board treatment device.

    On larger vessels grey water is tanked, but seperately from black water.

    Steve
     
  5. Submarine Tom

    Submarine Tom Previous Member

    Yes, it's a "black and grey" situation.

    -Tom
     
  6. rwatson
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    rwatson Senior Member

    Is that "toilet humour" there Tom :p

    Thanks KeysDisease - it does make a lot of sense, and now I have something else to consider for my project.

    I just have to ask - please tell us the "KeysDisease" meaning ? Is it an observation of the modern need to carry around lots of shiny metal objects in our pockets, or something more esoteric :)
     
  7. michael pierzga
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    michael pierzga Senior Member

    Well Mick in the perfect world it would be two tanks. Very difficult to design a two tank system with correct gravity feed plumbing runs into a small boat. Remember poop doesn't go uphill.

    Ive sailed several boats that had a single waste tank , grey black, for this reason. Perhaps double check your local requirements.

    Black water is troublesome on small craft. You will never find a pump out facility when on the road. Its a curse that some wise guy required small craft to adhere this blackwater holding tank requirement. Pumps, plumbing, vents, valves, deck fitting ...is a big collection of expensive junk to carry around on a small craft.

    Most small craft have a funky...IMITATION... tank system with a Y valve . They always have the Y valve selected to direct the " Sauce" overboard and NEVER use the black tank.
    Locally small craft builders use a cheap and cheerful waste tank system.... a meter or so of capped 8in ID PVC pipe..... "mini tanks " locate deep in the bilge that need no inspection clean out hatch because they can be thrown away after a few seasons.
     
  8. keysdisease
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    keysdisease Senior Member

    Hell R,

    I am a native of Miami Florida and just South is a string of islands curving 100 miles into the Florida Straits called the Florida Keys. This chain of islands has a reputation for "party" and "get away from it all" as well as world class fishing and diving.

    Many vacationers’ come for a week and spend a decade or two, we call that: Keysdisease. The disease manifests itself via a refusal to work, a strong inclination towards various adult beverages and the adoption of a new single syllable name like skip, or bud or buzz. A common T-Shirt slogan is "Come see the Keys on your hands and knees." The local business community supports this affliction by conveniently placing bars and taverns where needed.

    There is no cure. If someone is afflicted with said disease and is removed from the islands they typically will try and return.

    I spent 10 years living in Key West, sometimes known as Key Weird, which is the capitol of described asylum, and another 6 years in Islamorada which is just South of Key Largo. I know I had a great time in that period, or so I'm told, but I can't remember much. Thank goodness for video.

    How very appropriate this should end up in a poop thread.

    Steve
     
  9. TeddyDiver
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    TeddyDiver Gollywobbler

    :D I ended up here on a fishing trip in -86 with somewhat similar symptoms..
     
  10. pjssailor
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    pjssailor Junior Member

    Grey or Black

    My "home" territoryin on the American side of the Great Lakes near the Canada. Until I started to prepare to take a boat to Canada, I never thought about it. We had a tank connected to the stool and all the rest of the water was just dumped overboard. Gray and Black was only refered to on Motorhomes. Sometimes Dumpstations were separated, sometimes not. I discover that Europe is not nearly as strict about it as we are. Parts of Asia still value Black to fertilze their veggies. I was surprised to have a doctor basically say all the hulabalu is nonsense. So what do I know. My guess it that the human species has pretty good instints about sanitation and that we really do not need near as much as we have 99.46% of the time - but when one of those .54% events occur it is pretty catastrophic - like the plague.

    My self, I never pump my holding tanks unless I am well off shore. And I try not to use much soap in the shower if I am near the Marina.

    Interesting to hear realtively sparcly populated Austria has some concerns.
     
  11. bntii
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    bntii Senior Member

    Separate sure but gray goes overboard- no tank on most of the modest size vessels I see.
    The was a move afoot a couple of years back to license, inspect/issue a permit for gray water holding tanks on yachts here in the US. It was shot down..
    The Bay watersheds sees some 3 billion gallons of raw waste entering the estuary from municipal outflows. This is in addition to the billions of pounds of livestock waste and agricultural nutrients entering the Bay. Every bit counts but I feel that the issue of boaters and gray/black water is somewhat of a red herring.
     
  12. michael pierzga
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    michael pierzga Senior Member

    The advantage of tanks, from a design point of view, is the abilty to locate toilets, sinks showers...below the waterline or off centreline.
     
  13. rwatson
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    rwatson Senior Member

    Good to hear about other parts of the world.

    " sparcly populated Austria " - was that meant to be " sparcly populated Australia ?" - :), I also get "you are from Tanzania" when I am from Tasmania", or it could just be your spellchecker to :)

    But - back on topic, yes, we dont have nearly the population of lots of other parts of the world ( Austria had 8,190,000 people last year in 83,872 square kilometres, while Australia has 22,547,123 people in 7,741,220 square kilometres ), but the population is quite concentrated along the coast, and expecially in big cities like Sydney. The Sydney Harbour is very rigorous about boat effluent.

    In Tasmania, the environment gets a lot of emphasis as it is a big tourist drawcard, and there is lot of aquaculture on the coast, so the "clean, green" emphasis is in everyones mind. Not a bad thing, all in all.
     
  14. Mick@itc
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    Mick@itc Junior Member

    "Remember poop doesn't go uphill." You haven't worked in my job!!!:p
    Thanks for the reply...
    Regards
    Mick
     

  15. Mick@itc
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    Mick@itc Junior Member


    Rwatson...was in Tanzania the other day for the end of the syd-hobart. Nice towns in Tanzania and good beer...I expected Lions but got Cascade...;)


    Yes, back on topic...the Whitsundays are hype sensitive about it. Also Syd harbour as you mentioend and also some of the south coast harbours and lake inlets (eg Lakes Enterance). I think/believe I will be going with two seperate systems. My original logic for this was that I could use the grey water to flush the toilets (as per home) but then I realised I have an abundant supply of water just the other side of the hull. I'm assuming now that toilets are flushed with seawater???

    Mick
     
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