my COR 20 is driving me nuts!

[smitten with ocean life]

can someone help me figure out what is going on with my COR 20? i have 2 of them running on this tank. the one works great. i dont need to have it cranked the whole way up and its plenty of water movement. the second one barely moves water out the pipes even at full throttle. granted it does have a little farther to travel than pump number one. but still! these are fairly powerful pumps. i cant find anything plugging the pipes. i took the pump out and tested it- it blasts water fine. what am i missing?

 

[areefer01]

How are they both plumbed?
PVC, Flex/soft?
What size is the plumbing and if reduced, where?

I was going to suggest a bucket test but it sounds like you did this already. I ran into a problem with one of my Cor's and when I contacted support that is what they suggested. I should have thought of that. Anyway placing it in the bucket worked. Removed it, connected it back up to the skimmer, and no bubbles, same issue. Turns out a snail made it through the pump and lodged into the venturi blocking it :D

My point is that you can test in the bucket, it works, and may run into the same problem. The good news is that you know the motor block is running. Since the Cor 20 is the same size you can also swap them. Place the one that is not performing as you think place with the one that is. Take the one that is, place it on the one that isn't. Now how are they running?

If you can shut down the system for a spell, do side by side bucket tests at the same intensity? Do they look the same? You can also swap the power supply on the Cor 20 and make sure that is working.

Just create a list along these lines, test, then mark it off, move to the next.

 

[smitten with ocean life]

hard pvc. no reducer. that is a thought on swapping the pumps

 

[areefer01]

hard pvc. no reducer. that is a thought on swapping the pumps

Just to see if it follows. What size pvc?

 

[smitten with ocean life]

good question. 1in i think

 

[areefer01]

Sounds good. I recall the docs recommending 1 1/4" for maximum flow on the 20's but they also include the 1" slip. Anything under is not ideal and some hobbyist reported humming. Which that is not the problem here.

I like the idea of swapping them if you can, and then the power supply brick. You could also reach out to Neptune and submit a ticket to get in queue.