Choosing a sump size for a large tank

I'm planning a large upgrade when we get moved in to our new house we are in the process of buying and there was a concern brought up about the size of the sump I am planning on using. The tank will be a 240 gallon wide tank from glasscages (dimensions 72"x30"x25" tall) and I was just planning on using one of my existing 40B tanks as the sump just to house the skimmer / heater / return pump. I don't think I really need additional capacity for stability's sake since 240 gallons should make it fairly stable to begin with, but the concern was surface area for water displacement if you lose power.



Here is my thoughts on the sump:

Quote:

Originally Posted by rininger85 (Post 2458711) Well I understand that part of it, but that's just a matter of how full you run the sump, and what the overflow design is (how much water it's going to drain before suction break). I'm thinking I'm going to do a C2C (on the end, not the back because the tank will be visible from both sides, so the overflow will be on the side so it doesn't block view of the tank) with a beananimal overflow, so I would think the water you need to displace would be no more than 2x the capacity of the pipes. I'm planning on using a SRO5000INT skimmer which says it is 480gph water draw. So that is all that I plan on running through my sump, so I could get away with 1" PVC overflow because it should handle 960gph, but I will probably go 1.25" (1500gph) or 1.5" (2100gph) just in case I should happen to decide I need to add on other tanks in the future (which then might require a bigger skimmer / higher flow). So let's say it is a 1.5" PVC overflow, with SCH40 pipe that would be 1.5-1.6" ID. So let's say there is 10 feet (120", which I think is way more than I'll actually use, top of tank will be 6 feet from the ground roughly, and sump will be raised up 15-20inches or so off the ground just to be able to siphon out of it) of pipe for the overflow, according to a quick SolidWorks sketch that means it would have 98.96 cubic inches of volume. Google conversion says 99 cubic inches converts to a little under 1/2 gallon. So even if we say 1.5 gallons (full capacity of the beananimal overflows if they were all full of water for some reason) and say no more than 20ft (240 inches) of return pipe (I'm planning on coming up out of the sump, up to the top of the tank and run the return along the length of the top of the tank, up against the wall with a few different return lines coming off of the main that way its not all entering at one spot it will be spread out 4-5 places in the tank). So we're talking another gallon in the return lines so 2.5 gallons total in the pipes, plus whatever the water level in the skimmer is if it's above the water line of the sump? Let's say 7.5 gallons just to have a 3x safety factor. So a 40B is 36"x18", 7.5gal * 231 = 1732.5 / 36 / 18 = 2.67" that the water level should rise if you lose power. So again to be on the conservative side let's say we run the 40B sump 5" low (so 11" of water in the tank - the SRO5000INT has a recommended water level of 6.5" so I'd have to build a riser for it to sit on). That would give me an overflow capacity of a little over 14 gallons. This isn't giving you the full benefit of added water capacity in the sump, but with 11" of water in it you'd still be running about 30 gallons in the sump, so 270 gallons of water total. I might have the capacity to add an additional tank as a settling tank as well, but I haven't decided if I am going to or not yet. I have a pretty good idea of what the room dimensions are that I'm going to use for my fish room, but the layout is wrong because the water supply would have to go all the way around the room to be hidden in the walls, so I think I'm going to move the door from it's current spot to the opposite side of the room that way the tank will be closer to where the water supply is coming from so I can have my RO/DI and a drain conveniently located. I need to wait until we get in to the house to get exact measurements to start designing my room layout (I'm not sure if the MLS listing dimensions include the closet or not, so don't want to dive too deep in design then have to start over if the room size is wrong).

Is there something I am missing? Is there another concern beyond the water displacement when pumps turn off that I should be concerned with? I can go bigger if I need to, but I was planning on using tanks I already own. I am buying a 75 gal tank from my soon to be brother in law, but I want to use that for something else (stand alone refugium, non reef safe tank, or QT tank... haven't decided yet). Is there a reason beyond additional water capacity that I should use a larger tank for the sump?