BILGE PUMP

[jerry10848]

When I bought my ODay 28, the manual bilge pump on the aft wall of the cockpit didn't work. Due to the large amount of rain in the northeast this summer, my bilge keeps filling up (It appears to be a leak somewhere in the area of the starboard quarter berth, but that's another issue). Anyway, I was at Walmart recently and saw Attwood 500 gph electric bilgepumps for $10.00. So I came up with a brainstorm: install the pump in the bilge and run the 3/4" hose INSIDE the 1 1/2" hose used for the manual pump. Before installing the hose & wiring, I decided to see how well it worked by running the hose directly from the bilge up to the cockpit and draining it there. Much to my chagrin, the pump wouldn't pump the water up the approx 60 degree angle to the cockpit. My question is, would it not work because the pump was too small, or are bilge pumps of any size not designed to pump water at such an angle? I really know nothing about bilge pumps (obviously), manual or electric, so any imput would be appreciated. PS: I already know that "you get what you pay for".Thanks in advance.

 

[mrbill]

lift height?

How many inches do you need to lift the water?Of course the bilge pump will not get all the water out... it always leaves a 1/2" or so..if you put a bucket of water in bilge, can it pump that out? I would think it would pump out water about 24", as long as it doesnt loose the prime (enough water in bucket to keep pumping)

 

[Gary]

It's a bilge pump. Put the pump in the bilge. It will push more than it can draw. You will also need a foot switch to activate the pump automaticaly.

 

[Calif. Ted]

That pump is supposed to put out 350 gph

at 3.3.feet of head pressure. Head pressure is the weight of the water pressing back down and is about .5 psi per foot. This is a centrifugal pump which is not self priming and will not "lift" water, it must be submerged in the water to work at all. Your manual pump was a "positive displacement" pump which means it will pump air as well as water to create vacuum and self- prime. Positive displacement pumps are like a diaphram or piston pump, think of the piston in an engine, when it goes down it creates negative pressure in cylinder and the atmospheric pressure "pushs" the air, fuel whatever into that negative space.

 

[Gord May]

Excessive Head

As previously stated:There are two categories of pumps - Pushers (Blow) and Pullers (Suck).A centrifugal, like the Atwood is a pusher.All pumps are limited in the amount of head (resistance) they can work against.The Atwood can only lift the bilge water about 3 feet.If you reduce the effective inside area of your Manual Pump hose (to about 50%), you will reduce it’s pumping capacity to about 25%. Do not run the new 3/4" hose inside the existing 1.5" hose, unless you are abandoning that exist’g hose & pump.Regards,Gord