I need help with terminology on thru hull water intakes.

Discussion in 'Boat Design' started by ben2go, Oct 8, 2018.

  1. ben2go
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    ben2go Boat Builder Wanna Be

    I recently went boat shopping. I looked at a few ERs. In one boat, the thru-hull had a standard every day, I think 2 inch, bronze ball valve, aka 1/4 turn valve. It may have been larger. Sitting on top was a big tube, roughly 5-6" in diameter by 20 inches long, supported in about three places to a bulkhead. This tube had several other smaller bronze ball valves attached to it. It was made of what appeared to be bronze or brass. It had a removable top that sat just above the loaded water line. On top was a quick connector for either an air hose or a garden hose. I know what a true sea chest is, but I don't think that's what it is called. Could someone help me with the proper term for this multi-valve sea tube?

    I should note that this device is not a strainer. Strainers were attached after the bronze valves. This device wasn't the engine raw water intakes. The engines were running a sealed cooling system but the coolers were raw water cooled. Each engine had it's own through hull and seacock. I am ***-u-me here that this plumbing stack was for the AC, possible deck wash down, rear head, and other. Surely this device is a water supply for things with an intermitting usage. Based on my limited knowledge of sea chest design, I'm pretty sure this tube isn't capable of supplying a stack of 3/4 to 1.5 inch ball valves and sea strainers. I counted at least three valves but I think there may have been five total valves connected to it.
     
  2. fallguy
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    fallguy Senior Member

    Well, your math is off.

    A 2" pipe supports quite a lot of flow.

    The straight and simple method is area
    Pi*r^2

    So a 2" pipe has an area of 3.1415".

    And a 3/4" pipe has an area of 0.44". So a 2" intake supports 7 pipes 3/4". Of course, this is partially incorrect, but pretty close.

    The other guys can speak more to the details, but a 2" or (you said bigger) can support a LOT of flow. The other thing to consider is some things in a system do not typically operate simultaneouly and that can be figured in to avoid overbuilding plumbing systems. Also, if you bring in raw water to a device that only uses flow at 1/4" pipe (watermaker) the distribution can be oversized for simplifying the manifold.
     
  3. ben2go
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    ben2go Boat Builder Wanna Be

    Thank you for that. It may be helpful when sizing up a boat.

    I was mainly looking to know what that device is called. Hence my title for the thread. The guys that were opening up the boat for a survey kept calling it a seacock or sea chest. I don't think that is what it is called. I got lucky and happened to stop in at the right time to get a look at her nauti parts. LOL
     
  4. BlueBell
    Joined: May 2017
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    BlueBell . . . . .

    -water intake manifold
    -stand pipe
    -seacock
    -sea chest
    -stop cock
    -raw water intake
    -sea cock
    -valve
    -plumbing stack
     
  5. rxcomposite
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    rxcomposite Senior Member

    Do you have a picture of what you are describing? Could be a manifold or transfer manifold. This is a tube attached to the main intake valve, forms a T where several valves are attached.
     
  6. ben2go
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    ben2go Boat Builder Wanna Be

    No pic but I will try to piece it together. The thru-hull has a 2-inch ball valve on it. To make up for the hull's angle, there is an elbow attached to the valve. On top of that is the large tube standing vertically. It is capped with what appears to be a quick coupler for either a garden hose connection or air hose connection. This large vetical tube has smaller 3/4 to 1.5-inch ball valves attached to it, about five in total. These valves are staggered and directly opposite each other on the large tube. Three face directly to port and two directly to starboard. From there, there are marine hoses attached. The braided reinforced type. I couldn't tell where they ran to. I don't know if this makes any difference but it was mounted forward of the engines on the bulkhead, starboard side. The through hull was lower than the engine through hull. I ***-u-me that it's lower to not impede water flow to the engine through hull. I want to say again that the top of the tube was just above water line at gross displacement load. The water line was marked in several locations inside the hull. The boat was an older Carver. 70's ish. Nothing looked original in the ER.
     
  7. Blueknarr
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    Blueknarr Senior Member

    I suspect the garden hose attachment is so dock supplied freshwater could be used as an after voyage flush.
     
  8. ben2go
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    ben2go Boat Builder Wanna Be

    During my research, I found that it is common to use air fittings on a marine standpipe to blow debris out of the through hull. I think that is what the fitting was for. There was a small 8 to 10-gallon compressor sitting close by. I think one of the 3/4 inch valves supplied a deck wash pump. This boat is landlocked on an inland lake. Lake Hartwell, SC to be exact. A lot of debris can be found in our lakes, unfortunately.

    As to my question, it seems that the device I have described, as bluebell listed, is known by many different names. It seems people from many different trades have given the apparatus their own descriptive name based on their trade experiences. This makes conversations a bit tedious when discussing said apparatus with many names, many unknown.

    Thank you all for helping contribute to my continuing education. ;)
     
  9. BlueBell
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    BlueBell . . . . .

    "A picture tells a thousand names..." or something like that.

    Re: Qwik-Connect
    Compressed air can also be used to purge the pipes for freeze-up.
    Or a garden hose with a qwik-connect added,
    or any other appliance with a connector.
    Handy option.
     
  10. rxcomposite
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    rxcomposite Senior Member

    Attached is typical sea water intake.

    1. Thru hull- pierces the plating of the hull to allow water to pass thru.
    2. Elbow- needed if the hull bottom is not horizontal. Eliminated if the plating is horizontal.
    3. Seacock- Can either be a gate valve or ball valve with each having pros and cons. When closed it allows the strainer to be serviced.
    5. Skip to 5. This can either be a manifold, strainer or both according to the design.
    a. When it is just a manifold, it allows the distribution of water controlled by several valves. It can be vertical or horizontal. The water can be for cooling or deck wash.
    b. When a strainer, there is a cover (5a) screwed or threaded so that the top can be opened. The top is higher than the waterline so that it can be serviced during an emergency even when the engine (with its cooling water system) is operating. There is a strainer inside which can be pulled out and cleaned if blocked.
    4a/4b are valves which allows the distribution of water to machineries. Can lead to port or starboard.
    6. Fittings. Can be quick release or threaded. It allows service water to be fed if the seacock is closed. Air is sometimes pumped in to purge the manifold of debris/seaweeds if the manifold/strainer is not being used.

    There are other designs of course but this is the basic.
     

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  11. ben2go
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    ben2go Boat Builder Wanna Be

    That line drawing is spot on. That is exactly what I was looking at. Thanks for posting up. I've never seen one before. I also have not been around many boats over 30-foot in length and been able to peer into the ER or bilge. Most boats I have seen have one of two ways to distribute water. The most common was multiple through hulls with a ball valve and strainer. The other was the same except after the strainer there was a water distribution manifold with several ball valves feeding different systems.
     
  12. rxcomposite
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    rxcomposite Senior Member

    It depends on the requirements. Most engine manufacturer would require a dedicated thru hull and strainer for the engine so for all other requirements, a distribution manifold is necessary.
     
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  13. phillysailor
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    phillysailor Junior Member

    If designing a new boat, I've a question about minimizing thru-hulls and optimizing water distribution onboard.

    Assume a 39' sailboat with a central cockpit, a diesel engine with a wet exhaust. Aft is a galley house, forward is a sleeping cabin with a single head & a composting toilet.

    Would creating a compartment beneath a cockpit lazarette seat to hold a 2" solid FG standpipe which extends well above waterline, to be cleared using a broomstick as was described earlier in this thread, make sense to supply the boat's seawater needs?

    The standpipe would have a removable fitting at the top. A large single valve off the standpipe would feed into a strainer, and then a distribution manifold would supply wash down pumps, galley sea water, refrigeration and AC needs. A separate thruhull would be in this compartment for engine coolant. The compartment would be accessed from well above heeled waterline, so any thruhull or hose failures would be contained. It would be convenient to have a wash down pump and an AC unit placed here. Hoses and wires leading from this compartment to the engine compartment located immediately inboard, the galley aft and the head/berthing space forward would be sealed with gaskets to maximize water integrity, and located as high as feasible.

    The second concept I've considered was two 2.25" ID cockpit drains from the central cockpit exiting the hull straight down always below the heeled waterline. These would not have seacocks, and therefore would be built as structural components. Graywater, AC, and bilge pump discharge would be plumbed into these above the heeled waterline, with back check valves to prevent reverse flooding. The use of sumps for the sink and shower would be necessary. These cockpit drains would be covered by easily removed gratings in the cockpit, facilitating regular scraping/scrubbing with a long handled brush on a stick.

    Worthy ideas?
     
    Last edited: Jun 14, 2021
  14. fallguy
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    fallguy Senior Member

    Why, 'well above waterline'? It will have an air pocket, so nothing will be primed.
     

  15. phillysailor
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    phillysailor Junior Member

    So that the top cap can be removed and the tube cleaned out, say of an obstructing plastic bag, without bringing much water into the compartment.
     
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