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Help with External Pump Setup

914 Views 5 Replies 3 Participants Last post by  Diana

I'm looking to add a spray bar along the top of the back wall to my tank. To power this i'm thinking about purchasing an External pump which will be housed in the cabinet under the tank. Probably a 500+ gph for my 125g aquarium.

Trouble is i'm quite new to this and have a few questions.

1) Should I use flexible tubing to connect to the IN and OUT of the actual pump?

2) Will these tubes then connect to PVC joints and pipes in the tank? Output being the spray bar design and Input being the water intake?

3) Once connected will the pump need to be primed? Or should it just start sucking water and sending it straight out?

4) If the pump doesn't have a speed adjuster is there something I can build in to speed up / slow down the outflow? A valve of some sort? If so, where would it go?

5) Once connected and working what is the easiest way to stop the pump for maintenance? Do I need to build anything in to the design to help disconnect it without water going everywhere?

I'm sure I have more questions but these should help get me started.

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· Registered
11,717 Posts
I have used external pumps for large fountains, but not indoors. They are common on swimming pools.
Most are plumbed for IPS, international pipe standard (or something) meaning that PVC fittings will work. You can use rigid PVC or flex. The benefit of rigid is that it will turn sharper corners so fit into smaller space. Unfortunately some of the energy from the pump is used to force the water through those sharp bends. Instead of 90 degree fittings try to find sweep 90s or else use 2 fittings of 45 degrees each. The savings (better pump efficiency) more than make up for the extra expense. Flex pipe avoids that issue, but it needs more space to turn a corner.
Some of those pumps are self priming, some are not. You will have to investigate the actual pump you are looking into. Make sure it is fish-safe, too. Some pumps are not.
Most pumps can be slowed down some. Use a ball valve. Put one each on the IN and on the OUT. To service the pump unplug it and close both valves.
To disconnect the pipes include unions on both the IN and OUT lines, closer to the pump so the ball valves are left connected to the pipes that are in the tank.
Be prepared for some water when you disconnect. Put the pump in a plastic storage bin and keep some towels handy.
A pump like this has no filter. You have 2 options: Internal (not good looking, and not a good way to go. External. The way it is done with external pumps in the garden (pond or swimming pool). The filter is a separate item from the pump, sits along side the pump and is plumbed to the pump.
Since all of this is a closed loop, with just the tank open, there is no risk of water on the floor when the power goes out. (Of course a fitting might fail or something, but that can happen with any sort of set up).

The more common set up for home aquariums is a sump.
A volume of water, open to the air under or along side of the tank. Equipment (including the pump) is submersed in the water. Filter media is in this box, too.
There is a pipe draining the water from the tank, and a pipe returning the water to the tank.
The tank might have holes drilled in the back or the bottom so the pipes pass through the glass with special fittings called bulkheads. If there are no holes then the pipe that drains the tank needs some very careful figuring so it works, and does not cause problems.

Things to watch out for:
If the power goes out the water can run backwards through the pump. Fill the box and overflow. The spray bar is near the top of the tank (usually) so the water would quit siphoning through when the level in the tank drops below the spray bar. Keep the spray bar as high up as you can, and include a check valve (flapper) in the line that goes from the pump to the tank. KEEP THIS CLEAN!!! This is how I have ended up with water on the floor.
The water can siphon through the other pipe, too.
If the tank is not drilled then you will be setting up some sort of siphon to get the water out of the tank and down to the pump. There are ways to set this up so that the siphon will hold the water in itself and automatically restart when the pump comes on again (after a power outage).
For the best design look up Bean Animal. This one is a special set up, not a retrofit into a currently running tank. Take the tank down to do the work.
Any siphon that goes over the rim can fail. There are special ways to make PVC do the job, and it takes careful measuring to do it right. The intake is up pretty high, or else there is a hole drilled in exactly the right place so the siphon stops after draining just some of the water out of the tank and into the box.

Plan for some extra space in the box to hold this overflow from the tank during a power outage.

Another problem: If there is not enough water in the system the pump can empty the box, all the water is in the tank, and the pump is running dry. Get a switch so the pump turns off when the water is too low, and turns on when the water level is back up to the right level.

· Registered
11,717 Posts
Yes, your plumbing is exactly right.

A closed system like you have drawn would indeed just stop running. No overflow problems. A sump can overflow. Check valve would only be for the sump, no need in the closed system. And, you are right, when you shut it off to service it any water in the pipes below the ball valves could come out of the pipes when you disconnect the unions.

To get more water movement I have Koralia power heads in all my tanks. My 125 gallon on down to 45 gallon tanks (roughly 500 liters down to 200 liters) have Koralias that generate over 1000 gallons per hour, (4000 lph) and are very efficient in their use of electricity. If they or a knock off are available to you it is a LOT easier than what you are trying to build. You can attach them anywhere on the tank and aim them where you want, so you can put one near the bottom and aim it toward the surface and get some pretty good ripples going. I often put these on one end of the tank. The force of the water movement is dampened out in the 6' long tank, but can be felt all the way across the 4' tanks.

You would have to research what filters are available to you. Make sure you read the fine print. Some filters are tested without the media in place and will report a very high turnover, but that is cut way down when the sponges and floss and so on are installed. Pretty deceptive! It is very rare to run a filter with no media.
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