Forums General Discussion Reducing thru-hulls

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    • #66851
      Anonymous

      Bob,

      My boat had 18 or 19 thru-hulls when I got her. I think I’ve shared this with the group before, but in case you missed it here is Silver Heels’ thru-hull assignment list as of today:


      Below-Waterline T-hull, Starboard Side #1


      Intake to sea chest, which feeds the following:
      – galley sink
      – watermaker
      – toilet
      – anchor/foredeck wash-down
      – anything else I might install in the future that requires seawater

      Below-Waterline T-hull, Starboard Side #2


      – engine raw water intake

      Below-Waterline T-hull, Port Side #1


      – galley sink drain

      Below-Waterline T-hull, Port Side #2


      – holding tank overboard pump discharge
      – toilet discharge

      Above-Waterline T-hull, Starboard Side #1 (see photos)


      – midship side deck scupper
      – electric bilge pump discharge
      – shower sump discharge
      – watermaker discharge
      – head sink drain

      Above-Waterline T-hull, Starboard Side #2


      – aft side deck scupper
      – starboard cockpit drain

      Above-Waterline T-hull, Port Side #1


      – midship side deck scupper

      Above-Waterline T-hull, Port Side #2


      – aft side deck scupper
      – port cockpit drain

      Above-Waterline T-hull, Transom #1


      – manual bilge pump discharge

      Above-Waterline T-hull, Transom #2


      – engine exhaust

      There is also a small hole in the transom, well above the waterline, for the propane locker drain.

      One issue I encountered on my boat was that many of the “above the waterline” thru-hulls were, in fact, at or slightly below the present, painted waterline. So where I needed to keep the fitting, I removed it, sealed the hole and re-installed the thru-hull a little higher up. I opted to get rid of the forward cabin sink altogether, which used to drain through its own below-waterline seacock. The depth sounder transducer did not need to be thru-hull, and I scrapped the speed log wheel, which didn’t work anyway, and sealed the hole.

      Even with all this, I still have 10 holes in my hull, 4 of them below the waterline. There is room for improvement, for further thru-hull reductions, which I may get to in the future. For example, the manual bilge pump could share some other thru-hull exit.

      Tor


      Silver Heels, P-424 #17
      http://www.SilverHeels.us



      Original Message


      From: Robert Fine [mailto:]
      Sent: Saturday, March 08, 2008 10:25 AM
      To: Mailing List
      Subject: Re: seachest

      HI Tor,

      I agree – the engine and other uses should be different intakes.

      I think I’ll use a 1″ thru hull for the manifold and leave the other 1″ for the engine. Still, that only removes a couple of thru hulls. I also have 7 1-1/2″ drains (cockpit-2, deck-4, galley sink 1), 1 1-1/2″ head overboard, 2 5/8″ overboards for head/vberth sink drains. I think I have 19 thruhulls all together.

      My head and galley use the same intake thruhull – which I may just use for the whole.

      Still there are WAY too many holes in the boat. I’m not sure what the best way to deal with this is- I’ve thought of removing the deck drains and putting in hausepipes for drainage, or moving the thru hull to accomodate a simple elbow and then out the hull 6″ or so below the deck. Ugly, but removes large hoses and valves that are nearly impossible to get at.

      That may be next year’s project… Or one of them.

      Bob

      On Sat, Mar 8, 2008 at 10:14 AM, Silver Heels < (<email address>)> wrote:

      Bob,

      As fanatical as I am about reducing the number of thru-hulls in my boat, I still opted for a separate, dedicated
      thru-hull & seacock for the engine raw water intake. Everything else aboard that uses seawater – the galley sink,
      watermaker, toilet, anchor/foredeck wash-down, and anything else I might install in the future – will draw from the
      seachest. Of those items, the biggest consumer is likely to be the deck washdown pump up by the bow anchors, a Shurflo
      Pro Blaster, and that only pumps 4 gpm during its occasional use. So I’m not too concerned about having a huge thru-hull
      for the seachest. What I installed comes down to a 5/8″ ID hose fitting, which I believe will suffice. Remember, Dashew
      is accommodating a larger vessel with every imaginable bell & whistle. Our needs tend to be more modest.

      I’m still not decided whether to just beef up the lid and maybe the rest of the box of the converted shower sump I have
      already set up as the seachest, or to scrap it and build a PVC manifold from scratch. As for location of the PVC option,
      what you suggest sounds right to me.

      Tor


      Silver Heels, P-424 #17
      http://www.SilverHeels.us



      Original Message


      From: Robert Fine [mailto: (<email address>)]
      Sent: Saturday, March 08, 2008 9:17 AM
      To: Mailing List (Mailing List)
      Subject: Re: sea-chest

      Hi Tor,

      Seeing those manifolds, I think I could very well do with that, longitudinally along the hull below the show/head area.
      Even better than a big seachest. Or, longitudinally under the galley.

      You’re right about the 6″ thing. It might not be the best idea, or even necessary. Most seawater flows are very low
      (including the engine cooling). So, a two inch pipe should be more than enough. (remember a 1″ hole in the hull is
      supposed to provide 1000 gallons an hour, so 2″ should be nearly triple that. Good enough to wash dishes, pump the
      head, cool the reefer, wash the anchor, etc.)

      Your thoughts?

      Bob

      On Sat, Mar 8, 2008 at 8:53 AM, Silver Heels < ()> wrote:

      Bob,

      Where in the boat are you planning to put your 6″ PVC pipe seachest? You thinking of about, what, a 2-foot length? Are
      you planning for at least one end to unscrew to provide access to the inside for periodic cleaning? Any other thoughts
      on the design?

      Here are a few relevant notes from Steve Dashew’s “Offshore Cruising Encyclopedia”:

      “… it’s vital that the plumbing be either level or, better yet, plumbed with a slight rise. This prevents air locks.
      When there are dips or loops, water flow is restricted and centrifugal-style pumps don’t work well.

      The attached illustrations represent “three different approaches to PVC-based intake manifolds on a salt-water system.
      Two-inch (50mm) Ts and elbows are used, then reduced down to the needed size as they run along the manifold. The PVC is
      quite strong and not subject to electrolysis. However, it does need to be mounted where there is no danger of being
      stepped on, as it will not survive that sort of abuse.
      Tor


      Silver Heels, P-424 #17
      http://www.SilverHeels.us



      Original Message


      From: Robert Fine [mailto:
      ("><email address>)]
      Sent: Friday, March 07, 2008 5:21 PM
      To: Mailing List (Mailing List)
      Subject: Re: shower sump & sea-chest – Epilogue

      Hi Tor,

      I like your idea, but I think I’ll make my seachest out of 6″ PVC pipe with endcaps -Someone else here did something
      similar.

      I’m thinking of taking the sump out altogether as a simple strainer and pump would be far more useful. I have the switch
      in the head anyway since there’s no automatic float in the sump. Also, it would give me much better access to the bilge
      now that I put a holding tank in there.

      Bob

      On Fri, Mar 7, 2008 at 5:12 PM, Silver Heels < ()> wrote:

      Paul,

      This afternoon I tried out my seachest, converted from the old shower sump box. Boy, you were right about the water
      pressure (2 emails below)! That rigid lid in which I had such confidence bulged up noticeably when I opened the seacock
      and pressurized the box. Everything held and the system works as intended, but now I’m not comfortable with the strength
      of it for the long term. I’ll either beef up the box & lid with additional fiberglass, or just scrap that altogether and
      build something more substantial from scratch.

      Tor


      Silver Heels, P-424 #17
      http://www.SilverHeels.us



      Original Message


      From: Silver Heels [mailto: (<email address>)]
      Sent: Sunday, March 02, 2008 1:19 PM
      To: Mailing List (Mailing List)
      Subject: RE: shower sump & sea-chest

      Hey Paul,

      I believe it was Hans Solo who said, “Never tell me the odds!”

      I intentionally placed the thru-hull for the intake seachest down low so that it would produce positive water
      pressure,
      thinking this would assist all systems to draw more easily and have an ample supply of water flowing back into the
      seachest. The intake is also forward of all discharge thru-hulls to help insure it draws clean water. The fiberglass
      sump box in my boat is pretty hefty. No way the water pressure you describe is going to break it. It’d take a
      hard blow
      with a small sledge to do that. The lid is 1/8″ solid ‘glass, perfectly rigid, and secured by about 30 screws. I think
      it’ll suit admirably, but the proof will be in the use. I’ll let you know how it all works out.

      Tor


      Silver Heels, P-424 #17
      http://www.SilverHeels.us



      Original Message


      From: Paul Lefebvre [mailto: (<email address>)]
      Sent: Sunday, March 02, 2008 12:56 PM
      To: Mailing List (Mailing List)
      Subject: RE: shower sump & sea-chest

      Tor:

      While it looks like you have already done most of the work on the shower
      drain, you may find one of the following of interest. I recently purchased
      on of these as my hose fittings on the hold sump had failed. Being self
      contained, along with a float switch, means you can leave it always on and
      never have to worry about the shower drain. The pump inside is a low cost
      Rule bilge pump, so replacement when it breaks should be pretty easy.

      http://www.boatersland.com/ru97shdrkit.html

      The work you have down on the sea-chest looks good and that looks like a
      great way to reuse the old fiberglass shower sump. However, the engineer in
      me isn’t very comfortable using a component designed to be at atmospheric
      pressure as a pressure vessel. Even if it only saw a 3 ft head of water,
      this would generate 1.5 psi pressure With the cover at 8″ x 15″ or 120
      square inches, this would generate 180 lbs of pressure on the cover. It may
      even be more than this in healed or high waves. This unit may be able to
      withstand this, but it is almost 30 years old and it does now have 7 or 8
      new 1″ holes in it.

      Hopefully it holds well when you check it out in the near future.

      Paul
      Boundless #28

      From: “Silver Heels” < (<email address>)>
      Reply-To: Mailing List (Mailing List)
      To:
      Subject: shower sump & seachest
      Date: Sun, 2 Mar 2008 11:10:22 -0500

      Good day Bob,

      The shower sump pump had died some time in the past and the PO, lazy…
      fellow that he was, simply allowed the shower to drain into the bilge. This
      is a practice more common than you might suppose, but one I have never
      tolerated on my own boats. I plumbed the shower drain directly to a 12-v
      water pump (with an inline strainer just before it) mounted at the bottom
      of
      the locker beneath the head sink, and from there overboard. I have to
      switch
      on the sump pump several times in the course of showering, when water
      begins
      to puddle in the shower pan, but I located the switch just outside the
      shower stall so it’s easy to reach it. I’m looking for some kind of plastic
      grating to set down in the shower stall, raised up an inch or so off the
      sole, to keep my delicate toes out of the water that puddles in between
      sumps, but I’m basically happy with the set up even now.

      The intake seachest draws from a dedicated thru-hull that I installed about
      6″ forward and lower than the box. It feeds everything in the boat that
      uses
      seawater except the engine, which has it’s own, dedicated seacock. I must
      say, though, that I have not actually sealed and tested this seachest yet.
      Soon. It’s on the list.
      Tor


      Silver Heels, P-424 #17
      http://www.SilverHeels.us



      Original Message


      From: Robert Fine [mailto: ("><email address>)]
      Sent: Sunday, March 02, 2008 10:01 AM
      To: Mailing List (Mailing List)
      Subject: Re: Raw Water strainer placement

      Hi Tor,

      Where does your shower drain now? Also, where does the water for the
      sea
      chest come from?

      Thanks,

      Bob

      On Sun, Mar 2, 2008 at 9:34 AM, Silver Heels < (<email address>)> wrote:

      Eric,

      I moved my raw water strainer from it’s original position. Where it
      was
      blocked access to the shower sump box, which I converted to a seawater
      intake seachest (although I left the engine’s raw water intake separate,
      with it’s own seacock). As you can see in the attached photo I only moved
      the Groco off to the side. That worked out well.
      Tor


      Silver Heels, P-424 #17
      http://www.SilverHeels.us



      Original Message


      From: Eric Lorentzon [mailto:
      ("><email address>)]
      Sent: Sunday, March 02, 2008 8:31 AM
      To: Mailing List (Mailing List)
      Subject: Raw Water strainer placement

      Hi Folks –
      I am replacing the simple in-line water strainer (oem) on my ’79
      424.
      Looking for advice on placement / mounting for the Perko that just arrived
      from Santa – or maybe it was an early easterbunny dropping…..Also should
      I
      replace the raw water intake while it is out of the water too – it is OEM
      as
      well.

      Thanks –
      Eric
      “Navasana” #70


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