pump question.
 

i have setup a new tank. i have my ro water in it testing for leaks with the pumps running. the closed loop pump doesnt seem to be pumping as hard as i expected(1800 gal/hr). do the pumps pump less hard in freshwater? its running at like 500 i would guess.

The water shouldn't matter. Most likely a plumbing issue. What pump is it and what size pipe did you use. You will need 1 1/2" to get full flow of 1800 GPH through a single pipe.

its a mag 18. the pump it self has a 3/4inch in and a 3/4inch out. i have a 1 inch plumbed to the intake and 3/4inch out. its got about 4 feet to push the water.
http://www.mops.ca/cgi-bin/SoftCart....b2d+1112378920

Try plugging in your setup into this head loss calc to find out how much you actually are pumping into your tank.

http://reefcentral.com/calc/hlc2.php

I believe the recommended size pipe for the MAG 18 to achieve full flow is 1 1/2" in and out despite the thread sizes they have. It is kind of decieving. If you want to save the plumbing you have in place, try twinning the return pipe. Two 3/4" lines will approximately equal a single 1". It will improve the flow somewhat, but still not up to maximum.

thanks for the input.


Richard