Next message: Dan Stone: "Re: T&T: A Water Heater Question"
If a bilge pump switch is mounted low enough that a very small amount
of water activates it, it will cycle almost continuously because most
bilge pumps can never get the last bit of water out of the bilge.
Also, when the pump is shut off by the switch, the water in the hose
from the pump to the through-hull will run back into the bilge.
Depending on how long the discharge hose is, this could be enough
water to activate the switch again.
The usual practice is to mount the switch an inch or so higher than
the pump inlet. This ensures that when the switch is activated there
will be enough water in the bilge for the pump to get a "grip" on so
it can pump it overboard. When the water level drops to the point
where the switch is opened and pump stops, there will still be that
inch or so of water in the bilge. But the drainback from the hose
won't set the pump running again.
There are other types of bilge pumps that don't have the drainback
characteristic, or you can do what we do and use a small shop vac to
get that last gallon or so out if we want to :-) Also some pump
control panels have a switch with a spring-loaded position to turn on
the pump manually to get out the last bit of water the pump is
capable of getting out. Then the switch can be set back to automatic.
____________________
C. Marin Faure
GB36-403 "La Perouse"
Bellingham, Washington
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