Plumbing question - 2 tanks, one sump

[Blue Z Reef]

So here’s the deal, trying to figure out how to approach this…my main display is in my living room, it’s 210 gal with sump below. I want to have a frag tank setup in my office.

 

To achieve this, I would have to plumb under the house. Not a big deal for me, just wondering if this poses any issues?

 

The plumbing will have to drop about a foot below the floor and about 10-15ft horizontal before going back up and into the main sump.

 

Obviously I’m doing this for overall ease of maintenance as my tank is fully controlled by apex and has ATO/AWC/Dosing running on it.
 

My only other thought if the drain posed some sort of flow issue would be to have a dedicated DOS to do AWC between the display and frag tank to stabilize them together.

 

Thoughts? Does frag tank size matter for this? Debating if I want to do a 4x2 tank or something small like a 22gal aquamaxx tank or something? I will definitely have to calculate how much extra water volume I have in the sump, but I’ve got some room still.

[islandVib3s]

Thats tough, if your main is setup for auto waterchange,can you route it to the frag tank,instead of a waste container?. Idk it sounds complicated because of the lift. My multiple tank systems work in gravity. Main drains into secondary and secondary into sump. For my add on tanks,I just plumb it into the sump, drain into sump and pump back to display.  But again its gravity. 

[Blue Z Reef]

Can’t do AWC drain into frag because it would then need an additional line removing water for that to work. A DOS can theoretically do AWC up to like 30 gals per day so if a stand alone DOS was swapping 30 gals between my main and the frag tank, theoretically the chemistry would be consistent between the two. I know the DOS is capable of the lift as my current display has the DOS in my garage a story below the tank.

 

The main thing I’m concerned with in doing a plumb from frag to display sump is that it isn’t just a downhill run since the tanks are on the same story of my house, the part running underneath poses some potential drain issues. I’m not sure if there is enough pressure from the drain to overcome the lift from below into the sump without some sort of weird drain issue happening. Maybe not but I’m not 100% sure so that’s why I’m wondering?

[cjmdh]

It will work as long as the frag tank is higher than the sump AND your sump can handle the extra volume if both main and frag tank return pumps are turned off.  

[obrien.david.j]

Thoughts:

• What you described is completely doable.  (but frag tank drain has to be higher than lip into the sump, plus sump must handle extra volume - per @cjmdh comments)
• As noted, there's not that much "head pressure" on the return line.  I'd personally upside it significantly.  Something like a 2-2.5" pvc pipe.  larger volume, even with less head pressure/lower natural flow speed.
• I'd put a clean out drain under the house, on the lowest point of the plumbing.     Maybe even a hose connector to make it easier.
• unless under your house is heated, I'd wrap the pipes in insulating foam.    My system is half in the garage, and Oregon cold days make a heck of a dent on temp.