I replaced two PSK 2500s on a SWC250 Skimmer. From the old broken pumps I swapped the bottom collars which were fitted with venturi nozzles. The old pumps had needle wheel impellers. The new ones do not. My other skimmer runs just fine with a Rio 2500, regular impeller and venturi valve. But these PSK 2500s are very loud when I try to run them how the originals were run. Also no micro bubbles. If I pull the tubes out and the fittings for the venturi tube the pumps are silent. But obviously no bubbles without venturi. What am I doing wrong? This system ran like this without being loud. Now with brand new pumps I am not able to yet get it going.