External Pump

[Mrchase74]

Reefers,
Here is my next problem. I have an external pump I'm wanting to mount above my sump due to space constrains however I can not seem to get it to suck water up into drive pump to start the re-circulation... Any thoughts would help thanks

 

[AZDesertRat]

Centrifugal pumps will not suck water up. They require a flooded suction meaning the pumps suction or intake must be below the water surface level of the sump. For reliability you will need to drill your sump and mount the pump in the stand next to it. Some people will use an up and over suction design but it is a disaster waiting to happen when the power goes off. All it takes is a small air bubble in the line and the pump will not re prime and burn up.

I prefer internal submersible pumps unless it is something larger than 1500 GPH when submersibles become harder to find. The heat generation is really no different and the submersible will always be quieter and more compact.

 

[Mrchase74]

This pretty much seals the deal on this ideal of mine. I will need to do two internals and call it a day. Thanks for the insight...

 

[AZDesertRat]

How big are your display and sump? Two pumps would put out a lot of flow, probably much more than you will want to run though your sump and would create microbubble problems even with baffles. A good number for return pump flow is 5x the display volume so a 100 gallon display would need 500+/- GPH etc.
If your sump is on the small side you would have water whistling through the sump but if it is larger, say equal to the display you could increase the GPH and velocity with no problems.

You make the rest of the flow up with powerheads or a closed loop system. I use two Evolutions 1400 powerheads controlled by a Reefkeeper Lite switching back and forth every 30 seconds on the wavemaker function. Thats a max of 12 watts for 2800 GPH versus 60 or more watts for around 1000 GPH from a return pump or maybe 1300-1400 GPH with a closed loop.

 

[Mrchase74]

To AZ,
My display is 90g and my sump is about 40g. I was looking to have just one pump running all my under tank needs as you read my early post. However it looks I will have to run two internal pumps. One to re-cir the water to the tank and another one to supply water to all reactors. which is not a problem I was looking to just have one pump do it all.

 

[Mrchase74]

Ok is there a way to change the external pump to be a siphoning pump vice needing to be at sump level?

 

[AZDesertRat]

The only safe way to use an external pump is to drill the sump and install a bulkhead an ball valve on the pump suction side strictly for isolation and maintenance. I recommend no elbows or bends in the suction line as they cause head loss, always place the return pump so the suction is fed in a straight line. The problem here is it takes up a lot of real estate so som people oversize the suction line up to a 1.5" or 2" to reduce suction loss due to friction in fittings and elbows.

Centrifugal pumps cannot be converted to suck, it would require a self priming or jet pump and neither are very efficient so eat electricity 24/7/365.