Assistance Needed W/ Bilge Pump (Again)

[Bill Roosa]

More on head

For the record a pump with a 10' head is not putting out all that much pressure. A column of water 1"x1"x10' is only going to weigh 4.33 lb. 4.33 PSI is what the pump is supplying at 10' of head. A check valve can take 3 PSI to open it so you can see that there is not much left over to get the work done.

 

[Franklin]

Bill

Read your definition of what a head is and then read what his setup is. I think you will find that it is nowhere near 10 heads. The key word you are missing is VERTICAL.

 

[Fred Ficarra]

This is soooo much fun.

 

[Bill Roosa]

Oh I get It Franklin

I KNOW he does not have 10' of head to over come. That is why I said check your wires. My 10' of head comment was only to note that most of these pumps will never have a problem pumping from the bilge unless you put a blockage (check valve, kink in the hose) that consumes the head before it get to the thru-hull. Head is the sum of the height of the water in the circuit, the pressure at that point and the velocity at that point. Conservation of energy says that the head is constant at all points in the circuit. So at the pump the pressure is high but the height is low and at the thru-hull the pressure is low but the height and velocity are high. height1+pressure1+velocity1 = height2+pressure2+velocity2  0 + 10 + 0 = 4 + 0 + 6 dummy numbers for illustrationfor any points 1 and 2 in the circuit. You have to put in a lot of constants in each term to get them into the units of height and I'm not going there tonight.Interestingly the loss due to friction in the circuit does not effect the equation. The velocity just slows down as you get more friction. Which is what you would expect as more friction means less gal/min.BTW head is measured in feet/meters not "heads".Roosa FamilyTRITIUM

 

[sailaway78]

Bilge pumps

There is lots of technical advice on here, some of it good, some meaningless. First thing I would check is to make sure the polarity is not reversed. These pumps will not pump squat when running backwards. Ground is also a very good place to look. I do not like these pumps at all for my primary. I use a diaphram pump, with an elecronic switch for my primary pump, a rule 2000 with a regular float switch as a secondary. Both have auto/manual switch on them. The diaphram pump can be mounted high, and will self prime and pick from at least three feet below the pump, will work fine with the rotation either direction. They are expensive, when compared to the impellar types.