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How do bilge pump thru hull fittings work?

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  • How do bilge pump thru hull fittings work?

    I'm looking to install a bilge pump and plumb it straight up about a foot and a half feet into my splashwell. So, the pump hose will be straight vertical. What is to prevent water from the splashwell, or discharge from the pump, from entering back down the hose? Do these fittings have some sort of check valve on them?

    Any recommendations for fittings would be helpful.


  • #2
    Re: How do bilge pump thru hull fittings work?

    No, they don't have check valves. Why go into the splashwell? Boats are always rigged for overboard discharge.

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    • #3
      Re: How do bilge pump thru hull fittings work?

      Plumb it thru the side of the boat....well above the waterline. Don't run it into the splashwell. The splashwell has only 2 small drain holes and a good bilge pump can pump water faster than a splashwell can drain it.
      1975 Starcraft SS-16' / 1977 Evinrude 75hp now w/ CMC power trim and tilt
      17p prop- 36 mph @ 5900 rpm ( 2 people, 12 gals fuel, 2 batteries)

      1975 Starcraft Super Sport- Resto currently "in progress"
      http://forums.iboats.com/showthread.php?t=547770

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      • #4
        Re: How do bilge pump thru hull fittings work?

        Any thru hull fitting with a check valve would be inappropriate for the discharge line from a bilge pump, so you'll need to find a location which is high enough (well above the waterline) and mounted horizontally. This may require the use of a 90 thru hull as shown here. Whether the water discharges directly overboard (which is the preferred method), or falls into your splashwell shouldn't make a whole lot of difference, but I'd have to see your splashwell to make that judgment.
        Attached Files

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        • #5
          Re: How do bilge pump thru hull fittings work?

          Most bilge pumps I've been around have a pretty high output as mentioned. If you plumb it straight up into your splashwell, you might be creating a fountain. Go out the side like Bonairll said.

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          • #6
            Re: How do bilge pump thru hull fittings work?

            If you want to keep the thru-hull fitting lower to the water line, just put a higher loop above the thru-hull well above the water line.
            Don S.

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            Please, no PM's (Private Messages) regarding boat/engine problems.
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            • #7
              Re: How do bilge pump thru hull fittings work?

              I'm a fan of mounting the fitting as high as feasible. God forbid that your boat is seriously swamped....you're gonna want the thru hull fitting to be above the flooded water level, so that the bilge will be able to pump it out quickly.

              JMO
              1975 Starcraft SS-16' / 1977 Evinrude 75hp now w/ CMC power trim and tilt
              17p prop- 36 mph @ 5900 rpm ( 2 people, 12 gals fuel, 2 batteries)

              1975 Starcraft Super Sport- Resto currently "in progress"
              http://forums.iboats.com/showthread.php?t=547770

              Comment



              • #8
                Re: How do bilge pump thru hull fittings work?

                Sounds good, but bad when your bilge pump empties onto the dock or someones feet on the dock. Been there done that.

                Click image for larger version

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                Don S.

                sigpic

                Please, no PM's (Private Messages) regarding boat/engine problems.
                That is what the forums are for.
                Only forum/moderator issues will be answered in PM's.

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                • #9
                  Re: How do bilge pump thru hull fittings work?

                  Originally posted by Don S View Post
                  Sounds good, but bad when your bilge pump empties onto the dock or someones feet on the dock. Been there done that.

                  Click image for larger version

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                  don don't you have to have a vacuum break added in the loop line unless you are sure the output will never be underwater

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                  • #10
                    Re: How do bilge pump thru hull fittings work?

                    Out the side and high. Don't use a cheap plastic thru hull as the UV will eventually cause it to fail. There are other materials but stainless steel is the best way to go.
                    EdgeWater 205 EX
                    Yamaha 150
                    2012 Dodge Hemi

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                    • #11
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                      Re: How do bilge pump thru hull fittings work?

                      Originally posted by glenn property of pam View Post
                      don don't you have to have a vacuum break added in the loop line unless you are sure the output will never be underwater
                      Not as long as it's above the normal water line. Maybe 8 to 12" above the water. Just not so high that it dumps on the dock when tied up.
                      Don S.

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                      Please, no PM's (Private Messages) regarding boat/engine problems.
                      That is what the forums are for.
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