Is my pump cavitating?

[pleasants9]

I just recently purchased a 125 system that was running. I think the previous owner was trying to do too much with it and i am simplifying it down. One issue i can't seem to figure out is the pump keeps intermittently blowing bubbles. It is a reeflo Dart hybrid external pump. I keep watching the intake and i don't see it drawing in any air but everynow and then i hear a change in the sound of the pump, followed by a stream of airbubbles in the return line blown into the tank. The bubbles are driving me nuts. Is my pump cavitating? The intake is a soft 90 degree elbow facing down then pumping the water laterally through the sump into the pump? https://imgur.com/a/GzpYpCx

https://imgur.com/a/05DXFrg

https://imgur.com/a/Zj3OOBZ

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[Dross]

It probably is cavitation unless the line is above the water level and air is being pulled in at some point. Make sure the suction line is not too small or otherwise restricted. You really should have a 2" suction line for that pump at full flow. The suction head requirements of the pump go up with the flow rate so if you can throttle it back it may eliminate the cavitation.

 

[ca1ore]

Doesn't really sound like cavitation to me if it is periodic as you describe. As suggested, try choking down the pump output and see if it goes away.

 

[pleasants9]

It does have a 2 inch intake, so i guess that's good to go? It also has a ball valve at the output so i will close that off a little and see what happens.

 

[mcgyvr]

Can you please try getting the images to work... They aren't in your first post..

Typically pump manufacturers put stipulations like there must be "X" amount of straight pipe directly off the input before you can have an elbow..
Its hard to understand what you have as far as that goes..

Is the water being gravity fed into the pump? Not sure it is either from your description.. It needs to be..

 

[pleasants9]

Alright I was at least able to get links to post successfully. Restricting the flow slightly with the ball valve seems to have solved the problem. If I understand this correctly that means i can add some more head pressure to the return, meaning if I wanted to plumb in a manifold and t-off a feed to run through my chiller, I could do such?

 

[mcgyvr]

If I had to guess I'd bet that the water level in the sump is too low and you were getting a vortex generated there that on occasion was sucking air down into it..
Raising the water level would solve that..

You can certainly add reactors,etc... though and see how that goes.. I would still raise the water level some..

Remember that section is going to change based on evaporation and it may be fine today but let a gallon or 2 evaporate and it may start sucking air down again..

 

[pleasants9]

If I had to guess I'd bet that the water level in the sump is too low and you were getting a vortex generated there that on occasion was sucking air down into it..
Raising the water level would solve that..

You can certainly add reactors,etc... though and see how that goes.. I would still raise the water level some..

Remember that section is going to change based on evaporation and it may be fine today but let a gallon or 2 evaporate and it may start sucking air down again..

Vortex was my first thought. I stared at the intake for 20 min one day and never saw air get pulled in which is when I became puzzled and reached out for help. I have an ato on the sump to ensure water level is maintained to also ensure consistency with the in-sump skimmer in another chamber. I will see about raising the overall level of the sump though, jus have to make sure I don't max it out so it overflows when the return pump is secured for any reason.