DIY Sump Flow

Written by dr. samuel helms
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DIY Sump Flow
Sumps help remove chemicals such as nitrates, phosphates and organic matter from the water. (Medioimages/Photodisc/Photodisc/Getty Images)

Proper water flow through your sump is important for the health of your aquarium fish. A sump is a container outside of the display aquarium but connected to the aquarium's water system. A sump is most commonly used to store filtration devices, such as granular-activated carbon (GAC), filter mesh, sponges and a protein skimmer. Having the filtration in the sump keeps the clutter out of the display aquarium and increases the amount of filtration you can add to the system. Since the sump is primarily a filter, you need to have the proper flow through it to yield the best filtration possible.

Skill level:
Moderately Easy

Things you need

  • Return pump
  • PVC plumbing

Show MoreHide


  1. 1

    Calculate the ideal flow through the sump. Ideally you need between four and 10 times the total water volume of the display tank to flow through the sump per hour. If you have a 50 gal. aquarium, you need between 200 gals. and 500 gals.per hour (gph) flowing through the sump.

  2. 2

    Subtract the flow restricted by the plumbing system. Some aquariums come drilled to allow water to drain out and flow into the sump and the size of the hole may restrict your water flow into the sump. A 1/2-inch PVC has an ideal flow rate of 420 gph, 1-inch PVC is rated at 960 gph and 1 1/2-inch PVC is rated at 2,100 gph. If you have a 100 gal. display aquarium, the ideal flow through the sump is between 400 gph and 1,000 gph; however, if you have 1-inch PVC into the sump, your maximum flow rate can only be 960 gph.

  3. 3

    Based on the flow rate, determine the size of the return pump you will need. The return pump sends the water from the sump back into the aquarium. Pumps come with a "head loss" chart that shows what the maximum flow is per vertical feet the pump has to push the water. For example, a pump may be rated at 500 gph, but if it has to push the water up 10 feet, the flow may drop to 300 gph.

  4. 4

    Build a "T" into the plumping coming from the return pump. A "T" is a line coming off the plumbing from the return pump to the aquarium, created by using a "T" PVC joint. The additional line is fitted with a ball-valve to adjust the water flow and the pipe leads back into the sump. This way you can reduce or increase the flow into the aquarium without creating back-pressure on the pump. The harder the return pump has to work, the shorter its usable lifespan will be.

Tips and warnings

  • For reef aquariums, the flow in the aquarium is much greater than the flow through the sump. To create the extra flow in the aquarium, use powerheads and/or a closed loop system.
  • If you are using a protein skimmer, the flow through the sump should match the gph of the skimmer. If your skimmer can only handle 100 gph, the flow though the sump should be close to 100 gph to allow for maximum filtration.
  • Too much flow through the sump can create waterfall-like noises and small bubbles in the aquarium. Make sure the flow through the sump is calm and that bubbles are filtered out with a sponge.

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