That's right Russ! In leakage would be at least 5 times the flow rate of a typical 1200 gph pump on a good day. IMO, Using 4000 and 5000 gph pumps should be the norm and excepted minimum for emergency dewatering pumps.
It also goes to show that plugging the hole and plugging it well is a bigger priority than dewatering. Rule 56D 4000 GPH Marine Bilge Pump, Non-Automatic, 12 Volt https://www.amazon.com/dp/B000O8B7LO/ref=cm_sw_r_cp_apa_i_1Q2qCbPE6BPMB Josh Muckley S/V Sea Hawk 1989 C&C 37+ Solomons, MD On Sat, Jan 19, 2019, 1:06 PM Russ & Melody via CnC-List < cnc-list@cnc-list.com> wrote: > Hi Josh, > > Just for fun I dug out an old textbook and > estimate that a 1 1/4" through-hull opening about > 3' and a bit below the waterline will allow 100-120 gpm into the boat. > > The Rule 1200 gph hour is probably a lot less > after discharge head and hoses losses are calculated into it. > > If anyone is really worried about emergency pump > I suggest a nice little gas powered pump. Of > course it probably will refuse to start when you need it! :) > > Cheers, Russ > > > > At 12:23 PM 1/15/2019, you wrote: > >.... > > > >I'm preferential to a float type auto switch > >wired in parallel with the manual switch. My > >auto float switch is mounted above the pump and > >only turns on when a considerable amount of > >water accumulates. Under normal conditions I > >manually pump the bilge down and the float just > >catches it when I've abandoned the boat for weeks on end. > > > >I have a check valve. There I said it. In a > >perfect I world have a very high capacity > >"emergency" pump and associated auto float > >mounted just above the float for the lower > >"normal" pump. The emergency pump would not > >have a check valve. It would have a high loop > >to avoid a siphon but nothing to prevent > >backflow. It would also be as short and > >straight of a run as possible to the > >discharge. In this way I could ensure the > >emergency reliability and capacity of an > >emergency bilge pump by keeping it dry and > >rarely using it. I would retain the normal > >bilge pump's ability to pump the bilge to its > >lowest reasonable level. Both would work automatically and manually. > > > >The pump I have is 1200 gph (20 gpm) or 4 x 5 > >gallon buckets per minute - more flow than I can > >move manually but not much. Once, I > >accidentally left the transducer plugs out when > >launching the boat. We discovered the > >situation before water got to the floor boards > >but not before a considerable amount of water > >had made it in. Once the situation was > >corrected the bilge pump continued to run for > >what seemed like the better part of 5 > >minutes. The point being, 1200gph sounds > >big... It isn't. If I had a shaft seal that > >failed, the pump almost certainly would not have > >kept up and that is the least catastrophic emergency I can think of. > > > >Josh Muckley > >S/V Sea Hawk > >1989 C&C 37+ > >Solomons, MD > > > > > _______________________________________________ > > Thanks everyone for supporting this list with your contributions. Each > and every one is greatly appreciated. If you want to support the list - > use PayPal to send contribution -- https://www.paypal.me/stumurray > >
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