how does this sump work

I think his "overflow" is a straight siphon, or is driven by the HOB impeller, and not a proper inner/outer box. That would be a (if not the only possible) cause of a "hard-to-balance" system.



I don't see the outline of an inner box through that...

 

he could try to turn the impeller off(un plug) after the siphon starts, that way it would be easier to balance, and be a true overflow.


If that doesn't work he needs a completely new overflow box(a real one).

good catch

 

The biggest problem with no inner box is the potential for a lost siphon on a power outage, assuming some conditions are met involving siphon tube length and the water levels of the DT and outer box. Overflows are engineered with an inner box to keep that balancing act simple. The inner box also gives the possibility of surface skimming; a straight tube won't do that, which would be a decent portion of the point of running a sump.

He could either buy a new overflow box from someone like eshopps, or build an inner box to attach to this one. Or he could balance it, without that impeller running, if that's been going on. A bit tougher, but definitely not impossible.

I'm just really not sure on the setup of the overflow because there's no pic of it, or description.

 

we don't know there is no inner box yet, in fact most powerfilters have a inner box now(granted sometimes its crappy). If you look at the pics, I kinda think I see one. also If you look at the tube for the siphon, it looks too thick to be a regular powerfilter tube. I think its a legitamite overflow although a homely one.

 

I would guess that he upgraded the tube to a thicker one to accommodate more flow, if anything. I want to see if he has more pics/info though.

 

atleast every hob I have ever had had one(but like half of them were the same brand), But they didn't work unless your tank is completely full.

look at the middle of the overflow box in this pic there is a divider, you need to zoom in.

 

That's not an inner box. That's a baffle built-in to the outer box. The inner box goes inside the tank. Here's a quick refresher on typical HOB overflow construction:



Now that you mention the attention to detail, though, that seems to be a Penguin single-wheel powerfilter converted to this use; I had a few of them over the years. Very good filters. But they definitely don't have an inner box, just an outer box with a baffle to allow a centrifugal pump to work properly in the system.

 

oh you were talking about something like a surface skimmer box.
anyway with that baffle it still shouldnt lose suction unless theres crazy evap or the siphon tube is too short to go below the baffles height.

 

Well, we still need to hear back about the impeller; that's the big potential issue.

 

The best advice we can offer for now is get a proper overflow box, as you have already figured out the DIY equipment really requires you to understand how it works in the first place especially if your not the one that made it!

this should work much better for your setup...Reef Aquarium Filtration: Eshopps Overflow Boxes