How to Plumb an Aquarium Sump or Wet/Dry Filter System by Keith MacNeil, MarineDepot.com Reef Squad

Before we dive into the actual plumbing aspect of the article, we will go over exactly what a sump is, what a wet/dry filter is and which would be the best choice for your aquarium system.

We will then show you how to get water from your aquarium into a sump or wet/dry filter and ways to return the water back into your tank.

What is a Sump?

A sump (in aquarium terminology) is a vessel or vat set below your display tank to receive drainage. Unsightly equipment like heaters, protein skimmers and fluidized bed filters can be setup incognito inside the sump outside your display.

What is a Wet/Dry Filter?

A wet/dry filter is essentially a sump with biological filter media. The media is stored in a container above the water inside the wet/dry filter so water can trickle over it (instead of having it submerged). Bacteria will utilize oxygen from the air instead of your aquarium water, thus helping to keep the water more oxygenated.

Berlin Sump

Wet/Dry Filter

Wet/Dry Filter

Do I Need a Sump or a Wet/Dry Filter?

Live rock acts as the biological filter in reef and Fish Only with Live Rock (FOWLR) systems so there isn't a need for a wet/dry filter. But for Fish Only (FO) systems without live rock—or freshwater systems—the addition of a wet/dry filter can improve water quality and help breakdown fish waste. So, in summary: reef or FOWLR, sump. Fish only (without live rock) or freshwater, wet/dry filter.

Getting Water into a Sump or Wet/Dry Filter

One of the easiest (and best) ways to get water flowing into your sump or wet/dry filter is to purchase an aquarium that has a built-in overflow box. These tanks are often marketed as "reef ready," but don't let the name fool you: these aquariums are great for fish only saltwater or freshwater tanks.

The overflow box skims water from the aquarium's surface and drains it into your filter system. Inside the overflow box are holes drilled and fitted with bulkheads. Flexible or PVC tubing can be attached to the bulkheads to allow water to drain into a filter. Overflow boxes are made out of glass or acrylic and sold in vertical and horizontal configurations. Vertical overflow boxes reach from the top of your aquarium to the bottom where holes are drilled into the tank. Horizontal overflow boxes are positioned behind the aquarium near the water surface. Holes are drilled into the back pane of the tank for bulkheads.

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vertical overflow box

Behind-the-scenes look at a vertical overflow box. Note the water level and splashing.
This caused quite a bit of noise and was later fixed by making the water level higher.

If your aquarium isn't "reef ready" and you are unable to drill the tank, CPR produces several hang-on back alternatives. Hang-on back overflow boxes hang over the back rim of your aquarium and siphon water from the tank down into your filter system (view a demonstration here).

Now you know how to get the water out of your aquarium. Up next: how to connect the overflow to the sump or wet/dry filter.

The easy answer is tubing. But which type of tubing works best? Is it rigid PVC (like schedule 40), flexible PVC, spa or vinyl tubing? Actually it's whichever works best for your individual needs. With limitless combinations of overflows, sumps, wet/dry filters and tank sizes, having the freedom to select the plumbing that works best for you makes installation that much easier.

For example, if it's a straight shot from the overflow bulkhead(s) to the sump or wet/dry filter inlet, rigid PVC is ideal. If your overflow bulkhead is on the right side of your tank and the filter inlet is to the left, flexible PVC, spa or vinyl tubing will make setup much easier than conventional PVC.

After you've determined which type(s) of tubing work best for your aquarium system, begin hooking up the drain lines. Best piece of advice: keep it simple. Avoid bends. If you have questions, contact us!

Getting Water from the Sump or Wet/Dry Filter Back into the Tank

We should preface that there are many ways to approach this task. Entire chapters in books are dedicated to this very subject. We therefore offer a simplified approach. We hope the information presented herein gives you the confidence to undertake this do-it-yourself project. But when you do it with us, you're never alone! We can help you with the nuances of your sump or wet/dry filter setup.

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Now that you've got the overflow hooked up, it's time to setup the return line to carry water from the filter back into the aquarium. To accomplish this feat, you'll need a water pump to push the water along. 

You can go with a submersible or external pump. As the name implies, submersible pumps are submerged in the filter water. External pumps sit outside the filter. The sump or wet/dry filter must have a bulkhead fitting present in order to connect an external pump.

Once you've figured out which type of pump to use, you'll again need to decide which tube material works best. As a matter of preference, I like vinyl tubing. It's just easier to use. But there is nothing wrong with flexible or rigid PVC.

Next up: fittings. In addition to pump and tube options, you'll also choose between various types of fittings for your plumbing handiwork. We'll cover return lines using submersible and external pumps to ensure your setup is covered.

External Pump Instructions

Water will flow from the sump through the bulkhead into the return pump inlet. It will then travel through the outlet of the pump back into the aquarium. This can be accomplished in a number of different ways.

Step 1

Connect the filter to the pump inlet using a bulkhead. I HIGHLY recommend placing a union ball valve (single or double) between the two so you can easily remove your pump without having to drain the sump or wet/dry filter. I'd also like to recommend using PVC and not vinyl tubing in this instance.

Step 2

Attach tubing to your pump outlet to run up to the aquarium. Once again I recommend using a union ball valve here so you can leave all your plumbing in place when it comes time to clean your pump.

Step 3

You'll need to decide which type of tubing to use and how you'll ultimately return the water back into your aquarium. You have a lot of options here so this might end up being the most difficult step. Remember to keep it simple and avoid as many elbows as possible.

You can use a simple U-Tube return or plumb a return manifold. You can also utilize one of the many nifty wave making devices on the market, like the Sea Swirl or Vertex MOcean Wave Simulation Module. Or you can use a combination of different tube types.

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Union Ball Valves

Notice the two union true union ball (red) valves. Using ball valves allows you to remove your pump
for cleaning without having to disconnect any of the plumbing. Can you spot my rookie mistake?
Elbowing the line from the pump inlet is a no-no since it can cause cavitation and send
microbubbles into your aquarium. I corrected this oversight by simply turning the pump around.

Submersible Pump Instructions

Step 1

Attach vinyl tubing to your return pump. You may need to add an inexpensive hose barb fitting if your return pump does not include the proper connection.

A submerged Mag-Drive 9.5 is used as a return pump inside a sump with vinyl tubing.

A submerged Mag-Drive 9.5 is used as a return pump inside a sump with vinyl tubing.

Step 2

Add any additional fittings that will make your system safer and easier to maintain, like ball and check valves. Add barbed insert fittings to the inlet and outlet valves using vinyl tubing.

Check valves prevent backflows of water when a pump is de-energized.

Check valves prevent backflows of water when a pump is de-energized.

Step 3

Finally, we'll need to return the water back into your aquarium. This may entail bringing tubing over the rim and into your tank.

Similar to step 3 in the external pump instructions, you've got some options to consider. You can use a simple U-Tube or opt for a wave making device like a SCWDSea Swirl or Vertex MOcean Wave Simulation Module.

Here is a quick shopping list of items you'll need for a submersible return pump:

Return pump » 3/4" hose adapter » 3/4" vinyl tubing » 3/4" insert fitting » 3/4" ball valve (or union ball valve to disconnect the pump without having to remove the return line) » 3/4" insert fitting » Vinyl tubing » 3/4" barbed "Y" fitting » Vinyl Tubing (x2) » U-tube with directional return (x2)

Flow Accelerator on a return line

I use a Flow Accelerator on my return line to increase the velocity of the water entering the tank.

Plumbing an aquarium with a sump or wet/dry filter may seem complicated or downright scary. But if you plan ahead, keep it simple and don't over think things, you'll be a DIY plumbing expert in no time.