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CPR CS50 Overflow Box


Item #: CR1511

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  • For glass or acrylic aquariums up to 60 gal.
  • Flow rate 300 GPH.
  • 6" wide
  • 3/4" bulkhead outflow
A built in overflow is the most efficient method of draining aquarium water to a filter. If your aquarium does not have built-in overflow, CPR Continuous Siphon Overflows/Prefilters are the best means for getting water from an aquarium to a filter system without expensive modifications to the tank. They quietly skim up to six times more water than units with tubes.

The advantages of CPR Continuous Siphon Overflows/Prefilters include:
  • Adjustable water level allows you to easily change the level in your tank.
  • Black top reduces algae growth.
  • Quiet operation.
Tip: We recomond the use of an Aqua Lifter pump with the CPR overflows for trouble free operation. Another alternative is to hook the bleed hose from the overflow to the air intake of a power head. This way the overflow will continue to wok if it drawes some air into it or in the event of a power failure it will restart.

CPR Diagram

Model Width A B C D E F G H I J K L
CS50 6" 6 7/8" 8" 1 1/2" 1 7/16" 3 15/16" 4 3/4" 7 1/4" 5 9/16" 4" 3 3/16" 3 1/8" 2 7/8"
CS90 7 1/4" 7 5/8" 9 1/2" 1 5/8" 1 1/2" 4 1/2" 5 1/16" 8 5/8" 5 7/8" 3 7/8" 2 1/8" 3 5/8" 3 3/4"
CS100 9 3/8" 8" 10 1/4" 1 11/16" 1 1/2" 4 11/16" 5 1/16" 9 1/4" 6" 3 7/8" 3 1/4" 3 3/4" 2 3/4"
CS102 9 3/8" 7 7/8" 10 1/4" 1 11/16" 1 1/2" 4 5/8" 5" 9 1/4" 6" 3 7/8" 3 3/8" 3 3/4" 2 3/4"
CS150 9 3/8" 9 7/8" 10" 1 15/16" 1 1/2" 5 3/4" 5 3/4" 9" 6 7/8" 4 1/2" 3 11/16"" 5 1/4" 3 3/8"
CS202 9 3/8" 9 3/4" 10" 1 15/16" 1 1/2" 6 3/8" 5 3/4" 9" 6 3/4" 4 1/2" 3 5/8" 5 1/4" 3 3/8"

Manufacturer information

CPR Aquatic Aquarium Supplies
In Arcata, located in Northern California, the sea is a way of life. From the advanced Marine Biology department at Humboldt State University, just up the hill from CPR’s headquarters, to Humboldt Bay, about a mile west, CPR is nestled in a perfect environment to develop equipment for marine aquariums. CPR was started in a small garage in 1987 to produce biological filters for local aquarists. People who used CPR filters were impressed by the high quality and affordable prices. Word spread and the company grew. Since then, CPR has expanded to a 10,000 sq. ft. production facility and has developed many innovative products over the years. CPR is incorporating new ideas and technologies all the time. Their goal is to allow aquarists to place the highest performing products in their tanks at reasonable prices.

4 Stars


Reviewed on
December 08, 2017

Yes, I would recommend this.

Perfect if you done want to drill your tank

Cons: Need air pump for strong flow

Best over flow if you don't want to drill your tank

Was this review helpful? 1 0


Reviewed on
February 22, 2017

Yes, I would recommend this.

Necessary Evil

Pros: Noise dampening features, low required parts design, siphon break recovery feature via external pump, easy to setup

Cons: Noisy, Dependency on external pump reliability for restarts.

I've never tried an overflow box before. This is a difficult review to write because I have come to understand the inherent challenges this solution presents as a product class as a whole. If you can't drill your tank or don't want to buy a reef ready one, then I think you are left with little choice if you want to use a sump instead of a canister. Here are some of the issues and how CPR has worked to reduce/resolve them: Noisy... Water running down a tube outside your tank is going to make a decent amount of noise. Not for use in a quiet space, I can hear water running even over the TV at decent volume. This unit has an adjustable air inlet/outlet above the bulkhead that allows you to eliminate "gurgling" - it works well. The siphon control with an added water pump helps avoid siphon breakage, and sometimes restarts after simulated power outages. Out of five tests, mine restarted the siphon 3 out of 5 times without intervention. Not the best odds if you ask me. To CPR's credit they are very upfront about this solution and state that if you can drill or purchase a drilled tank - they strongly recommend it. If you do purchase, inspect VERY CAREFULLY for cracks or damage and don't use it if it has any. Install it carefully, while sturdy - its acrylic and can crack. Any cracks or damage may allow additional air into the unit which can negate the water pumps ability to restart or hold a siphon. I do like that the CPR product uses minimal parts and install was a snap. Bulkhead connects are sturdy and haven't leaked a drop by just hand tightening it. If an overflow box is the only option, then i do believe this line is the one you should purchase.

Was this review helpful? 4 0

kevin kitchen

Reviewed on
December 02, 2016

Yes, I would recommend this.

Not quiet

If you're looking for quiet operation, keep looking. The overflow box itself is quiet but the gurgling coming from the bulkhead to the fuge in the bottom is loud. I bought the CPR recommended connection tube and there is still no relief from the gurgling sounds. No amount of adjusting the tube going into the bulkhead relieves the noise.

Was this review helpful? 1 0

nathaniel hobart

Reviewed on
July 02, 2016

Yes, I would recommend this.


I was scared of putting the drill to my brand new expensive 150 gallon tank. It was too big to lug to a shop to get drilled. This was the answer. Get an aqua lifter pump with this thing and you will never look back. The pre filters work great, you can drop some chemipure in the overflow... It's just a great product. Highly recommended if you are scared of drilling into your super thick shiney you new glass aquarium.

Was this review helpful? 0 0

jev deasa

Reviewed on
April 22, 2016

Yes, I would recommend this.

CPR CS overflow box

I've had this for almost a month now and it's been working fine. I'm happy with its performance. If you don't want to drill a hole on your DT, this would do the job just fine. I do recommend this product.

Was this review helpful? 0 0

bruce peace

Reviewed on
March 20, 2016

Yes, I would recommend this.

COR Overflow

Product is well made and does as advertised. I may have missed the opportunity to order the deluxe kit (with lid, pump, etc). Didn't see that option so I made my own.

Was this review helpful? 0 0

raul castro

Reviewed on
September 10, 2015

Yes, I would recommend this.


I hade this product for 3 weeks is great low noice level easy to use.... No more having to getting water in your mouth all you need is an aqua lifter and your ready to go... The only thing i dont like is having one more item plug into my outlets. Wish i did not have to have that aqua lifter pug all the time. I will try a valve to try and keep air out of the box and take the aqua lifter out and just use it when i need it...

Was this review helpful? 2 0

lee ross

Reviewed on
August 22, 2015

Yes, I would recommend this.


It is quieter than I expected. Works as advertised. Been running 1 day. Shipping was outstanding and everything survived the cross country trip in perfect condition. Thanks

Was this review helpful? 2 0

joseph morris

Reviewed on
May 18, 2015

Yes, I would recommend this.

Definitely recommend it....

I've have this over flow box running now for 3 years with no problems. One great tip is that I use floss in the box to filter and quite the suction of the water noise. I change it as needed but also keep my return set high below the water line so when my main pump goes off my refugium doesn't over flow... Great quality and would recommend..

Was this review helpful? 3 0


Reviewed on
May 15, 2015

Yes, I would recommend this.

Excellet flow

This overflow is excellent. The flow is high and works smoothly and quietly. The only difficulty is when the suction line connected to the pump gets plugged with a piece of goo, algae, etc. - when that happens the tank overflows the rim onto the floor. It is absolutely necessary to do regular maintenance to make sure that the suction line does not clog.

Was this review helpful? 0 2

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