Why is my closed loop pump making noise?

[foshizzle]

I installed a new Quiet One 4000 (rated at 1090gph at 0 head) running through a 3/4" Seaswirl on closed loop. Plumbing is a 1" intake bulkhead at the bottom of the tank that travels about 2ft horizontally and 30" vertically through 1" flex PVC. I also have a 1.5" ball valve installed directly after the pump. This is reduced to 3/4" where it enters the Seaswirl.

Every few seconds the pump makes a clicking/crackling noise?

I have opened the pump numerous times and everything seems to be working fine. There are no microbubbles so I don't think there is a leak. Is the flow restricted too much by the 3/4 Seaswirl?

http://i48.photobucket.com/albums/f243/shelburn61/P5230079.jpg
http://i48.photobucket.com/albums/f243/shelburn61/P5230081.jpg
http://i48.photobucket.com/albums/f243/shelburn61/P5230080.jpg

[jvetter]

I have a small quiet one pump plumbed externally like yours which I use to circulate my seawater makeup water tank. It makes similar noises while I am mixing up fresh saltwater, and there is undissolved salt passing through the impeller.

Is your intake sufficiently screened to prevent particulates from passing through the pump?

[foshizzle]

Yeah, it does make a similar sound to my salt mixing pump.
The tank is barebottom though, with no sand and very little detritus so I think it is more than that?

[nick18tjetta]

Probably not getting enough water on the intake side. Do you have anything that is restricting the intake?

[foshizzle]

A 1" strainer on the tank side of the bulkhead and a 1" elbow on the outside.

The pump intake is 1". Is 1" pipe too small for 1090 GPH?

[BeanAnimal]

It may be for that pump and each is different. I am not familiar with that pump, but it may be cavitating with that much 1" intake pipe in it.

[foshizzle]

How can I tell whether the pump is cavitating?

The tank is already full. Any way to fix the problem using the existing bulkhead?

[NanoReefWanabe]

i think it is cavitating aswell...

how much back pressure are you applying to the pump now?

if you can throttle it back a bit i would think it would stop the noise...if not then maybe you are not cavitating and there is something else amiss...

with my CL i had the return open and it cavitated liek crazy...i capped th return and drilled a couple holes in it and that solved the prblem..for me anyway..

[AZDesertRat]

Try closing the ball valve on the discharge a little at a time until the noise stops. You are restricting the pumps suction using only 1" pipe and having an elbow in it. Its best to always go up at least one size on the suction side of a pump whenever possible and not use any bends or elbows so there is no resistance. Every fitting adds resistance to flow. By closing the discharge valve some you match the input and output eliminating cavitation or starving the pump.