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Just above water line thru hulls

Discussion in 'Technical Discussion' started by Capt Ralph, Aug 7, 2015.

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  1. Capt Ralph

    Capt Ralph Senior Member

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    Any thoughts installing Stainless thru hull fittings just above the water line. Rite in the boot.
    Here, I know to ad sea-cocks. It is a FRP hull.
    Only S/S fittings I can find in reasonable cost have a hose barb included. Saw in the shed.
    Next, Bronze cocks over stainless pipe? Thinking Marelon now.

    Anybody mixed materials just above the water line before or has thoughts?
  2. dennismc

    dennismc Senior Member

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    I believe the do it in Europe but have an expected short life span, mixing dissimilar metals is always risky.
  3. Boatbuilder

    Boatbuilder New Member

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    Marine Hardware in Redmond, WA makes stainless thruhulls, Fisheries Supply in Seattle carries them, don't know who distributes them on East Coast.
  4. Capt Ralph

    Capt Ralph Senior Member

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    I was wondering if anybody had thoughts on S/S near the water, under waves (always wet with salt water) and sea cocks.
    I don't have a problem getting them.

    I have looked at the Perko chrome plated bronze thru hulls. No idea how long the chrome plate would last.
  5. dennismc

    dennismc Senior Member

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    What about straight bronze and paint them to match the boot stripe, Hatteras used to do that from what I have seen.
  6. Capt Ralph

    Capt Ralph Senior Member

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    Shiny "thingies" were spec'd.
  7. dsharp

    dsharp Senior Member

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    I've used the chrome plated perko thru-hulls and they hold up fine. Is a sea-cock required? I've always just made sure to have a well secured loop in the discharge hose. I bought a couple of the stainless thru-hulls with the barb but, ended up not using them. They appear to be well made but, that's not much of an endorsement.
  8. Capt J

    Capt J Senior Member

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    A lot of manufacturers use them and they last a long time and don't have issues. Longer than plastic/marelon ones. I don't know if I would mix brass and s/s. I think you'd probably be safe with a marelon seacock. A loop in the hose is a good idea also. I'm guessing you're replacing existing Marelon/plastic ones. What did the builder do on the inside of them (seacock or loop). Your customer better have a raft handy to keep them polished =)
  9. Capt Ralph

    Capt Ralph Senior Member

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    New install thru hulls.
    Original low fittings (below the boot) are bronze with cocks. These originals are below the water when the ship is loaded.
    Were adding some new A/C discharge and grey water (shower sump) discharges. At the top of the boot where new fittings are planed, will still be above a calm & loaded water line. Owner wants pretty & shinny fittings. Stainless and then chrome is all I could think of.

    I'll probabley go with stainless, cut the hose barbs off, screw on marelon cocks with 90 tails.
  10. Caltexflanc

    Caltexflanc Senior Member

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    My Hatteras had a whole bunch of through hulls near the water line... bilge pumps, shower sumps, aircon discharge, stabilizer cooling water, deck drains and so on. Not a sea cock on a one of them, just big loops where necessary. Frankly I don't see the point of a sea cock in that application, and apparently neither did Mr. Hargrave. The through hulls in the forward half of the boat had clamshell type fittings with the opening pointed aft.
  11. dennismc

    dennismc Senior Member

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    They should really have both check valve and seacock.
  12. Caltexflanc

    Caltexflanc Senior Member

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    Why? Check valves are a bad idea on bilge discharges, if they get jammed/gummed up, and they do you are SOL. That's the whole idea of having a loop well above the maximum heel of the boat.

    By the way, this thread got my curiosity aroused and it's a slow day around here so.. if you want your sea cocks here y'go...

    http://www.jamestowndistributors.co...e=Whitecap+Stainless+Steel+Thru+Hull+Fittings
  13. dennismc

    dennismc Senior Member

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    Not to rain on your parade, the idea of the c.v is to prevent downflooding in the event of a serious list, that's why certified vessels have to have them, also, many pleasure craft use that corrugated plastic bilge hose which over time will crack at the curve and thence the severe risk of flooding.
    YMMV hopefully
  14. Capt Ralph

    Capt Ralph Senior Member

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    My surveyor reports a loop higher than the loaded water level after a 7 degree list is good and not requiring a cock.
    Many of my A/Cs drain from much higher levels. That means a direct down drain so they are exempt. The grey water sump (shower), I may have a problem with. It's going to be pretty low in the hull. With such a small pump, tall head and then a higher loop,,, I just may use a cock and Whale check valve.

    That corrugated puke hose should be outlawed, IMO. You can not secure it, creates internal turbulence & restrictions and holds up like corrugated cardboard. For a few dimes more, a real hose should be installed and not thought about for years.
  15. Capt Ralph

    Capt Ralph Senior Member

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    Thanks to all for your thoughts.
    ,rc
  16. dennismc

    dennismc Senior Member

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    Transport Canada guideline for vessels that may carry passengers is a 40 deg list before any downloading may occur, highly unlikely in most environments yet some surveyors here suggest it as many pleasure craft will downflood at even 20 deg list which is still a lot.
  17. Pascal

    Pascal Senior Member

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    AC discharges can flood the boat so it's a completely different issue than bilge pumps and sumps. If the TH is close to waterline, you do want to be able to pull the hose for maintenance, descaling, etc... Without having to worry about water coming in though

    I would never ever rely on check valves for bilge or sump pumps, sooner or later they will get stuck or reduce flow. The right way to do it is to have a rising loop high enough

    Someone mentioned brass earlier in the thread, it should never be used in air con applications or anywhere where it will in constant use. Unfortunately many installers and surveyors use or miss them especially as some fittings are hard to find in bronze, especially male/male nipples. Have you ever opended an air con strainer only to have it fall off the the hose? Ever disassembled and aircon manifold or pump and found a fitting little crumble away? I have... Too many times :(

    My favorite set up is what hatteras used on earlier boats. They set up sea chests along the hull side ( my 53 has 5 total) to collect various discharges and dump then thru single fiberglassed holes at the water line. The only downside is that it makes it harder to troubleshoot air con water issues as you cant be sure water flows equally thru all air cons
  18. Caltexflanc

    Caltexflanc Senior Member

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    It is quite sunny and clear on my parade. Please cite this certification you speak of. AYBC prohibits check valves on bilge pump systems on the discharge side, they allow them on the suction side (still a bad idea IMO) to prevent back wash into the bilge when the pump stops, for pumps set up to have a suction hose and pumps that have one built into the suction side( the little low profile whales and the Rule knockoff of same are examples of the latter) The loop should be above the maximum heel of a boat ("a serious list" in your words), if the boat has listed further than that, it has much bigger problems.

    As for someone using that crappy hose, a check valve or sea cock ain't helping much there either.
  19. Caltexflanc

    Caltexflanc Senior Member

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    And furthermore read up on the Canadian requirements for bilge pumps . No mention of check valves there either.

    https://www.tc.gc.ca/eng/marinesafety/tp-tp1332-menu-521.htm
  20. Capt Ralph

    Capt Ralph Senior Member

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    Can you please point me to that ABYC text?