pump to small?
 

i just finished pluming my first ever drilled tank <was surprised no leaks:lol:> my question is i have to turn ball valve about 3/4 closed for my return pump to work and keep up with flow threw sump .is this normal?i bought a used pump off a canreef member and was told its a mag12 but it has no markings on it .its being a real pain to get system to work without overflowing or running dry depending on where i have valve.tank is drilled herbie style with a 1and 1/2 hole for drain and 2 1 inch return holes

I am no expert in this but all my tanks overflow line's are bigger then the return. Your return line's are bigger then overflow so they can't keep up to the overflow. Just a thought.

hehe no its a inch and a half pipe just wrote it wrong

well now I am at a loss, my 155 has 2 - 1 1/2" owerflow feeding sump, 1100 gph pump feeds 1 - 1" line that branches off into 4 - 3/4" lines into tank.

if its a mag 12 you shouldnt have any issues running dry. just add more water to the sump so it stays higher. or just leave it turned down a bit with your valve.

your pump can pump more water than it is getting 1.5" pipe will have a flow of 1200gph if there is no 90 degree turns or even if you are useing a flexable hose for every turn add 1 foot to the pipe. you can either add water or leave like it is and use the ball valve to adjust but don't get to much back pressure. I would add more water and a T or 2 going to more return pipes.
Bill

+1 it sounds like you just need to put more water in the return section of the sump. If you fill up your return section first, to the height of your baffle (assuming you have a baffle), then plunk the mag12 in and turn it on it will suck up water out of your return section fast and needs water to fill the return line. That's probably why the water is running low. Once the return pump is running, fill your return section to the level that you want to run it at. Depending on how large your return section is, this is the section that will show loss in water due to evaporation. So if it is a small section it will drop fast due to evaporation and you will need to top it up. The water level in the return section will also change with any change in your overflow box due to the herbie overflow. More water in the overflow chamber = less water in the return chamber of sump.

i when and looked up size of pumps and after mesuring my mag 12 its smaller so thing its only a 9.5 i think.i have 2 90 elbows on my feed line to sump .first area of sump 17 inches wide then goes over /under /over glass to where return pump sits in area 6 inches wide bye 8 inches deep

I'm with others, might be to do with volume.

To set level; with power on, fill display from sump until starts to overflow into sump, power off, let back flow until display stops draining, fill sump to the maximum level your comfortable with, mark max. Turn on pump, opening valve until until your drain flow max's out, mark water level in you sump say as max, power on. Your pump should be able to run without going dry to the 'max, power on' level, if not, your sump is too small. You can run your system below the 'max, power on' level to set heights for skimmer depth etc, not above.

With evaporation and not topping up (or having a ATO) you'll eventually draw air. With power on, never top up above the 'max, power on' mark.