NEED MORE POWAH! Talk to me about pumps please.

[Oreo]

Easy friend, before posting a photo you were puzzling over how to determine "head", Now you know.
Don't shoot the messenger.

Sorry, I wasn't directing that comment at anyone in particular. Just that I had done so much calculating & figuring that at some point I had to make a decision that I was confident with the answer I had found and it was time to move on to the next piece of the puzzle.

I must have been asleep when I looked at the picture. Completely missed the closed loop. You are correct, "head" doesn't come in to play at all.

Either You have a significant restriction in the supply/return or your pump is malfunctioning.

Have you considered removing the pump and testing it's actual output unencumbered by the rest of your system ?

The pump isn't malfunctioning. The pluming / filtration / etc is indeed restricting the flow and that restriction can be measured in "head" so head does need to be considered.

My preference is Little Giant pumps. I choose the 220v versions when possible to reduce electrical costs. They are slightly noisier than my mag 12 but far more energy efficient.
It's going to be a little tough to recommend a particular pump without knowing the rest of your system information, for example, how large is your tank ?
Turnover rate in a true closed loop system only needs to be high enough to provde adequate mechanical filtration. (See attached quote)

My 240 gallon / closed loop system has a 4X turnover and keeps the tank nice and clean. It uses a Little Giant MD-5 / 220v/ 950 GPH. I have a service interval of 7 days on the cartridges and loose 20-30 % of the rated flow by day seven.

My 100 gallon / closed loop system has a 5X turnover and uses a Little Giant 2- MD/ 500 GPH. I also service it every 7 days and loose 10-15 % of rated flow by day seven. The difference in loss is due to this tank being less heavily stocked.

Don't assume too much. Allow me to blow your mind: I'm looking for about 20x / hr of turn over. Stand back, don't worry, I know what I'm doing. I'm a professional. Sort-of.

Now, 220v you say? That's an interesting suggestion worth thinking about. Normally I'd just complain about not having 220v electric near by but this time is different because I could run the electric real easy.

You know anything about Iwaki pumps? They have a good reputation? I hear to go with their Japanese motors and they are very good. (Their American made motors are crap apparently?) I'll look into the little-giant pumps you're suggesting too since I didn't see any Iwaki pumps that used 220v electric.