Clear Bottom Overflows
Finally see what's in your overflow.
Overflows
100%  Cast Acrylic
 
Item
Dimensions
LxWxH
Price

OVR-SQ5
5"x5"x5"
$59
OVR-SQ6
6"x6"x6"
$69
OVR-R10X5
10"x5"x5"
$79
OVR-R15X5
15"x5"x5"
$99
OVR-R20X5
20"x5"x5"
$129
OVR-R24X5
24"x5"x5"
$149
OVR-R10X10
10"x10"x5"
$169
OVR-R36X5
36"x5"x5"
$199
OVR-R15X10
15"x10"x5"
$229
OVR-R48X5
48"x5"x5"
$249
1" Overflow Kit
1" bulkhead (1.75" hole)
$40
1.5" Overflow Kit
1.5" bulkhead (2.25" hole)
$48
Reverse Slope Machined Edges for Less Noise and Fewer Bubbles
Closed Loop Circulation Warning

Don't install your closed loop circulation input bulkheads below the waterline and then just put a strainer on it unless you have a Fish Only tank. If you have a reef tank, see what the experts say:

"We have seen many aquariums equipped with recirculating pumps with the intake plumbed through the wall of the aquarium (either a side or the bottom), and outfitted with a strainer to prevent fish from being slurped into the motor. This technique works fine for fish-only aquariums, but is a disaster in the reef tank. Don't make this mistake! Wandering clownfish anemones, loose mushroom anemones, algae, sea cucumbers, and other creatures end up against the strainer and often, through the pump. They become reef puree. The design of choice with this arrangement is to simply put the intake in the overflow."

The Reef Aquarium, Volume Three, Science, Art, and Technology (J. Charles Delbeek and Julian Sprung) Chapter 7, Water Motion, page 408.

This is probably the finest book available for discussing water quality, filtration, water motion, and a variety of other important topics regarding the success of a reef aquarium. We highly recommend the book. But also note that unless you want a recipe for disaster in your reef tank you need to use overflows for all closed loop circulation input bulkheads. If your existing overflow has enough flow you can simply drill another bulkhead hole inside the overflow box and add the additional pipe to connect your closed loop pump. Or, you can order a custom overflow from Austin Oceans and protect your reef tank inhabitants while providing the closed loop circulation to improve their health and growth.
 
Closed Loop Circulation? Click Here.
The arrow shows where the back of the overflow (and the tank wall) goes. After you drill the correct size hole in the back of your tank (or side if you are installing the overflow on the side of the tank), unscrew the bulkhead and slide it through the just drilled tank hole. Then slide the overflow onto the bulkhead. Then screw the bulkhead on tight, with the gasket on the outside of the tank.
Bulkheads and More Plumbing Fittings:
In addition to Overflow Kits, we also get requests for bulkheads and other plumbing fittings. Take a look at our Plumbing Fittings page and see if you want us to send you some plumbing fittings along with your order. If you order these fittings along with a larger order we'll send them with no additional shipping. If all you order is the fittings then there will be a small shipping charge added.



Yes, there is a bottom on this overflow! With Clear Bottoms you can see what's in the overflow (like fish, or snails, or an anenome) or even what under the overflow without problem. You can see from the picture how easy it is to see through the crystal clear bottom. Someday all overflows will come with clear bottoms.
Custom sizes aren't a problem. We can make an overflow that fits your tank and overflow rates.
Clear Bottoms Let You See Inside
5"x5"x5" Overflows
5"x5"x6" Overflow
Our Overflows come undrilled. Use the same holesaw that you use for the back or side of the tank to create a matching hole in the overflow at the appropriate place for your water flow.

We can't tell where you want the water level in your tank so we can't drill the overflow for you. If you don't have a holesaw or can't figure out how to drill the overflow, email us and we can drill it for you if you take a few measurements for us.
We can do custom sizes too. Generally a custom size will cost the same as the next larger standard size from the table below.
New! Check out our Turbo-Overflows.
Turbo charge your tank circulation with a Turbo Overflow Kit. Get 3-5X increase in circulation (in gallons per hour) using our eductor circulation add on to your Austin Oceans overflow. Click here for more details.
Overflow kit pricing now includes free shipping.
Custom Sizes Available
Step by Step Installation Instructions

What you need to install the bulkhead: a drill, a properly sized holesaw, a bulkhead, and the rest of the plumbing to attach the bulkhead properly to your sump (our overflow kit has the more difficult to obtain fittings).

  1. Get a bulkhead fitting (either purchase our overflow kit or get a bulkhead from your local HW or internet supplier)
  2. Make sure you know what size the hole needs to be for your bulkhead and get a holesaw for your drill of the correct size (again from your local HW or internet HW supplier)
  3. Now you need to have thought about the amount of flow you want through your sump and overflow. Some people recommend 5X your tank size or even lower flow (e.g for a 100 gallon tank that would be 500 GPH). We like a higher amount of flow with a minimum of 10-15X but you also need to understand how much flow your sump can support without producing excessive bubbles. Again, using a 100 gallon tank example, the Sequence Reeflo Dart or Snapper are popular return pumps. While these pumps are rated at 3600 GPH and  2500 GPH respectively, the effective flow rate will work out well for a 100 gallon tank, often in the 10X-15X turnover rate. Plus, if you have more flow than you want initially both of these pumps can be throttled back with a ball valve but give you the flexibility to add more flow in the future just by opening the ball valve a little (and they use less electricity when throttled back).
  4. Determine the size of the overflow you want. Our overflows will typically flow 100 GPH per inch of teeth at max capacity so I would plan on 50 gal per inch under normal conditions. If you want to get 1000 GPM of flow you would need a 20” of teeth. This could be two 5”x5”x5” (2 sided) corner overflows or a center 10”x5”x5” (3 sided) overflow.
  5. Determine the normal water level you want to have in your tank and place the overflow inside the tank starting with the water level halfway up the teeth (i.e. half of the teeth underwater and half the teeth above water). Note that if you don’t have any water in your tank yet you have to decide where you want the normal water level to be and orient the overflow at the proper height. Depending on your tank you may want to raise or lower the overflow a little. However, we do not recommend lowering the overflow where the teeth will be more than 75% underwater. You want some additional reserve in case you start to get (for whatever reason) more flow into the tank than expected. You want enough additional capacity left to handle any unexpected flow. Note that while this may be unlikely, we like designing reserve capacity into our aquarium systems.
  6. Once you know where the top of the overflow should be mark the aquarium with a piece of tape so you can move the overflow to the outside of the tank and match it up to the right height. But before you do that, get the bulkhead and your overflow kit – we recommend a Durso style plumbing kit to minimize water noise) and determine where to position the bulkhead or each bulkhead if you have more than one. Make sure you have room inside the overflow for the bulkhead and the Durso style fittings (i.e. don’t drill the bulkhead hole too high or too low). We like to position the bulkhead lower in the overflow than the exact middle but make sure that the hole you are drilling has enough room on the bottom for the bulkhead, the bulkhead gasket, and locking nut. Drill the hole in the overflow using the holesaw (remember, slow and steady with frequent breaks to make sure the acrylic isn’t getting too hot) then place the overflow on the outside of the tank with the just drilled hole next to the tank where you want to drill the tank bulkhead hole (using the tape you placed earlier to mark the correct height). Then use the hole you just cut into the overflow to trace the outline onto the tank where you want to put the bulkhead. Once you have traced the hole, remove the overflow and prepare to drill the tank.
  7. Slowly and carefully drill the hole in the tank, stopping to check that it isn’t getting too hot. You can also use a water spray bottle to cool the acrylic (use fresh water, not salt water). Once you finish drilling the hole, insert the bulkhead and tighten the locking nut. We usually orient the bulkhead so the long part of the bulkhead is inside the overflow and the outside of the bulkhead is almost flush with the tank. In this orientation we recommend placing the bulkhead gasket on the outside of the tank. Just in case it isn't clear, the bulkhead goes through the tank bulkhead hole and the overflow bulkhead hole - the bulkhead holds the overflow in place.
  8. Add the elbow or other Durso plumbing to the bulkhead inside the overflow and attach the close nipple and the tee to the outside of the bulkhead and connect the PVC pipe, Spaflex, or flexible hose from the tee to your sump.
  9. Turn on your return pump and watch carefully to make sure the correct water levels are maintained. If you have one of our overflow kits, use the valve at the top of the tee to adjust the amount of air entering the drain to the sump so that you minimize the noise of the drain. If you have a ball valve on your return to the tank from the sump, open and close the valve a little to vary the amount of water returned to your tank to make sure everything is working as planned. Your overflow should be self-correcting and should flow exactly as much water to your sump as you are flowing from the sump into the tank.
  10. If you have excess capacity on your return pump, you can add a tee with a ball valve to use the pump for any other water circulation uses, such as feeding your skimmer if it needs a pressure feed, feeding your calcium reactor, or feeding a Sea-Swirl or other return device.
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One of our latest custom overflows, this one is 16"x5"x5" and the other part of the L is 12"x5"x5". There is a matching overflow for the other end of the tank. This overflow goes into a tank that is flush against the back wall so all the bulkheads have to be in the side of the tank. This one will have two 2" drain bulkheads and a 1.5" input bulkhead for hidden returns plumbed inside the overflow.
have to be in the side of the tank. This one will have two 2" drain bulkheads and a 1.5" input bulkhead for hidden returns plumbed inside the overflow.
Installation Instructions:

Retrofit to an existing acrylic tank-Simply lower the water level, drill the hole for the bulkhead, and install the unit. The 1.5" bulkhead clamps the unit to the tank, and the gasket on the outside of the tank makes it waterproof. Remember that the top of the overflow box needs to be lower than the top of the tank.




Our overflows can help turn your reef tank into a high performance aquatic environment that will make your coral (particularly your SPS) really feel at home. Never install a simple bulkhead drain in your tank - it will only be a matter of time before a snail, or anemone or some other invertebrate gets caught in the drain and then you've lost a valuable animal and it's death will potentially foul your tank unless you happen to see it right away. Whether you need to skim water for your sump, your closed head circulation, or external fed powerheads you should use an overflow box to help protect your tank inhabitants and provide control over the amount of water leaving your tank. We offer standard overflows in the following sizes:

5" x 5"                1 bulkhead drain (1-1.5")
6" x 6"                1 bulkhead drain (1-1.5")
10"x5"                1-2 bulhead drains (1.5")
15"x5"                1-2 bulkhead drains (1.5")
20"x5"                2-3 bulkhead drains (1.5")
24"x5"                2-3 bulkhead drains (1.5")
36"x5"                2-3 bulkhead drains (1.5")
48"x5"                3-4 bulkhead drains (1.5")

IMPORTANT!
Note: The dimensions may be up to 1/2 inch
different than listed. The depth (top to bottom)
will be between 4.75" and 6.25" if we list 5". If
we list 6" then the depth can be between 5.25"
and 6.5". We have to cut between the existing
machined teeth so the dimensions may vary a little.
If you have an absolute maximum that you cannot
exceed (i.e. your tank is only a certain length) then say
so in the Special Instructions when ordering.

Custom Sizes Available

We also offer custom sizes including "coast to coast" or "Calfo-style" overflows that can stretch the entire back side of your tank. Prices will be as listed above for the next larger standard sized overflow. Add the custom size you want in the "Special Instructions" when placing your order. If you are doing something special, send us email at sales@austinoceans.com with your overflow size needs and we will quote you a price.

Custom Milled Teeth

These overflows can be used to retrofit an existing tank, or to add unique features to a new tank. Each overflow has custom milled slots that are smooth and closed at the top. This prevents teeth "break-out", and allows the water to sheet down the inside edge, which can greatly quiet the water flowing though the teeth.

A  great idea: Clear bottom overflows!


Features:


Flow rates:

The water rate though the teeth will determine the water level in the tank. Position the boxes so that if the teeth get partially clogged, the water will overflow in to the top of the box before it overflows the tank. The flow rates below are based on our testing, your results may vary as the rates depend greatly on your plumbing. Do not use the maximum flow rate, always leave at least 25% (or more) of a margin for buffer.


Note: your overflow can only flow as fast as water enters the overflow. If you have a 48" overflow and your water level is barely cresting the overflow teeth you may only be flowing 100 gph - or even 500. The above numbers are what you can expect if you are trying to flow more water. In general, we expect about 100 gph per inch of teeth if the water level is all the way to the top of the teeth. Most tanks have a water level lower - the typical numbers above assume that your water level is midway to about 2/3 up to the top of the teeth. Obviously if your water level is lower than midway up the teeth you will have less flow.

Options - Put options in Special Instructions when ordering



Overflow Plumbing Kits:

These kits include everything you need to plumb the overflow, available with the purchase of any overflow box. Use the included hose barb for clear vinyl tubing, or the female threads for hard PVC plumbing.

1" Kit:


1.5" Kit:


       


Custom 48"x6"x6" Calfo-style Center Overflow
This overflow goes in a reef tank with two corner 6"x6"x6" Turbo Overflows.
 
Holiday Sale!
10% off Foaminator MAX Protein Skimmers, all MoCalc Calcium Reactors, and all Kalk Reactors for orders placed by Dec 31, 2007.


Holiday Sale!
10% off Foaminator MAX Protein Skimmers, all MoCalc Calcium Reactors, and all Kalk Reactors for orders placed by Dec 31, 2007.