Gravity. Is it worth it's weight?

[fire&water]

Do you use a transfer pump from tank to pump or does gravity empty the tank completely?

It seems these pumps build pressure, not vacuum from the tank. Isn’t this double duty?

 

[Larry B]

Gravity will feed the pump. That said however, I do not let the level in my 500 gal. tank get less than 6"-8" above the level of my filtered outlet fitting. I am not sure if having a little extra pressure makes any difference but it gives me some peace of mind to think so.