When discussing a pump & overflow...

... what is meant by "having a... with 5 feet of head"?

... is it the same thing as the maximun shut off?

Trying to understand. Thanks for any input.

 

Head is the amount of back pressure the pump is forced to over come to pump water where you want it to go. Maximum shut off is the head that the pump can not push water past. Generally speaking the maximum height it can pump up to.

 

To add on to that.... head is vertical distance a pump has to overcome... gravity... measured in vertical feet. So your sump in the stand has a pump and it is 4 feet to the top of the aquarium that it has to pump up to.... you have 4 feet of head. More head, more resistence to overcome, less water moved. Cutoff head is the maximum vertical distance thew pump can lift water. A cutoff of 20 feet means at 20 feet it can't go any more.

Net head is the sum of suction head and discharge head. If a pump was sitting in two feet of water, and it had to pump 4 feet total up, then the net head is only two feet. Most people speak in net head, and most of our situations really only deal with net head since you might only have a foot of suction head in your sump. But in reality, if you have 12 inches in your sump, and 4 foot to the top of the tank, then your head is only 3 feet total that you need to overcome.

So when specing a pump, it isn't about how many GPM it puts out.... it's about how many GPM will it put out in your system when you account for your head. You need to figure than is so that when it is all said and done you have the amount of flow you need.

Some folks will relate piping resistance to head.... two 90 degree elbows generaly equals one foot of head. So for a plumbing system, you can get a rough idea of how much piping resistance you have measured in feet of head and add that in as well to get a pump that will give you the flow you need for your application.