return pump not performing

[sirruckus]

I got a used red dragon off a fellow reefer - 4.5m3 model (1200 gph) this thing isn't pushing even has hard as my Sedra 7000 (700 gph)

I've taken it apart and cleaned it, what could be the problem?

outlet is restricted to 3/4" lines rather than the 1"
inlet is a 90 degree elbow (proper size) - I've seen some diagrams for other red dragon pumps requiring a long straight tube as an inlet.

any thoughts on this would be appriciated

[Phil]

I'd say the 90 will greatly reduce the flow as will reducing the out put size right off the pump

[FishyFishy!]

I would stick with the 1" and lose the 90 to see if it helps.

What is the head height to your return?

[sirruckus]

head height is about 4' - although that wont matter when comparing the same condition to a weaker pump

I would expect some loss with the 3/4" line, but not 600 gph loss
I'll try changing the intake to a straight run.

the only other thing I can think of - is the motor is going - is there a way to inspect, or test?

I would think with the motor, it would either work - or not work

[mark]

for a 90 on the inlet read different places 3-5 times pipe diameter for minimum length of straight piece between pump and elbow.

seen also in Red Dragon manual here, pictures and everything

[sirruckus]

saw that, threw on a straight pipe -minimal difference (but better)

just trying to see if the previous owner has put on a different pump head. right now I have a 1-1/4 inlet and a 3/4" outlet (I thought I was reducing it, but i'm not)

I thought I had found somewhere that it was a 1" outlet

[sirruckus]

I talked to the previous owner, great guy, he suggested it might not be performing because someone had run it dry for a couple minutes, and offered a full refund.