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post #16 of Old 06-21-2013
Maine Sail
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Re: Pumps do not do what you think

This is not at all unusual for a centrifugal style bilge pump. I always figure on 1/3 or less of face value rating as installed.

Some things most are not aware of:

#1 These pumps are rated at the open bucket rate. This means a ZERO head rating.. This is a VERY DISHONEST way of selling a bilge pump to unsuspecting buyers..... I personally find this type of marketing disgusting at best. Almost as bad as companies selling "marine" tankless LPG fired water heaters that meet NONE of the safety standards. Caveat Emptor.......

#2 These pumps deal horribly with added head pressure and can pretty easily lose 50-75% or more of their rating as installed.

#3 These pumps are rated at charging voltages. This is NOT completely honest as most sailboats would not have the motor running when the bilge pumps was in use. All one needs to do is look at the amperage consumption to see how much the voltage can affect these pumps. A Rule 2000 will draw 12A at 13.6V and just 8.4A at 12.0V....... The current a pump draws is directly related to GPM/GPH volume

#4 Corrugated hose adds a LOT of head restriction.

#5 Check valves should not be used on the outlet of the pump because the pumps often don't have the oomph to overcome the standing water in the hose or the check valve sticks.

#6 Every elbow or turn adds more head restrictions.

#7 The height from bilge to siphon break creates even more head.

#8 Undersized wire can add yet more unwanted voltage drop to the pump causing even more reductions in output.

#9 Discharging below water, such as teeing into a sink drain, can also slow the pumps capacity...

-Maine Sail / CS-36T

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