Sump Design Resources

I'll toss some of this in the Wiki as well, from http://www.melevsreef.com/allmysumps.html

How does a sump work???
A sump gives you greater control over your reef or fish-only display tank. The benefits far exceed the risks, and thus most successful aquariums you'll see utilize a sump. Some even incorporate a refugium as well. Here are the numerous benefits derived from incorporating a sump into your current setup:

• Increased total water volume - This dilutes your water of accumulating pollutants, and helps avoid issues that occur quickly in sumpless tanks.
• Skims the surface - No more surface scum, just crystal clear water.
• Lowers temperature - I've observed a 2° F drop after the sump is installed.
• Hides equipment - Heaters, protein skimmers, monitoring probes, grounding probes and more can be moved to the sump & out of the display tank.
• Consistent water level - The display tank will maintain the same water level all the times; evaporation occurs in the sump over time (see auto top-off).
• Safe place to pour in additives - Adding chemicals or new (Reverse Osmosis De-Ionized) water in the sump allows it to mix before entering the display tank.
• Increased circulation - The return water from the sump is yet another way to move water in your tank. You can point the return outlet(s) in different directions to create flow, instead of putting more powerheads in your display tank!
• Increased oxygenation - As water drains into your sump, air mixes in the water, allowing beneficial gas exchange, releasing CO2 and adding fresh O2.

Optional Features:

• Automatic top-off device - Install an automatic float switch to add new water, as needed, from a nearby holding tank to keep your system filled up. closed loop system.
  
  
  
  
  
  
  
  
  
  Noteworthy Points:
  Green Light: Return pump ON
• Water rises to tank
• Return area lowers
• Display fills higher
• Overflow fills
• Overflow drains to sump
• Sump fills
  
  Red Light: Return pump OFF
• Residual water in plumbing drains
  down
• Drilled hole in return line
  breaks siphon
• Water in sump and refugium
  rises
• Siphon is maintained in
  the overflow box
• Sump is tall enough to hold
  excess water
  
  
  
  How does a weir, or overflow box like the above work?
  
  The way it works is that there is a baffle on the inside and one on the outside, to keep the 'bubble' of water trapped in that center zone (the inverted U) until flow is restored. If it has a leak, air will bleed in and water will go out, and the siphon is lost. So it has to be tested with water after it has been built. Take it to the sink, thread or snake in a piece of airline tubing into that chamber, and while water is filling the inner box, you suck out the air with your mouth on the end of the tubing. Then you watch it closely, to see if any airbubbles start bubbling up inside that chamber. If you see none, it is perfect. See this page for info about Durso Standpipe or Stockman Mod. Many discussions about these silencers can be found using the Search option on ReefCentral.com
  
  How do I determine what return pump I need?
  
  To establish flow rates, you have to get a pump that will match how fast the drain will flow. I have a 1" drain on mine, and because there is no volume of pressure over that drain (or bulkhead), my maximum flow rate is 300gph. If the bulkhead were at the base of the tank, and I had gallons of water pressing down due to gravity, it might drain as much as 600 gph. But that is not the case. In the outer box of the weir, there is maybe a pint of water, so it goes more slowly. You want to find a return pump that will match your drainline, but you also have to figure head pressure as well. How far does the pump have to push water back up to the top of the tank to refill it? The submersible pump in the sump under my 29g has to push water straight up 5 feet. So a Mag 5 at 5' pumps 300gph. A perfect match!
  
  Here's a chart of Mag pumps and head pressures: Charts for Mag drive application
  Courtesy ReefCentral.com, here is a head loss calculator
  
  
  
  
  
  
  
  
  
  
  
  This picture displays the return plumbing, including an additional horizontal valve feeding water to a refugium. The vertical section has a valve to bleed off excess water back into the sump. Everything you want to know about sumps - Part I
  Everything you want to know about sumps - Part II
  Everything you want to know about sumps - Part III
  
  I hope this helps you understand how a sump works, and how you can design one to your specific needs.
  
  12-12-2003 - How to design your sump yourself. Questions answered, details explained, and general comments.