DIY Backyard Budget Swirl Filter

budget swirl filter

There are so many ways to build a backyard budget swirl filter and I have seen some fantastic backyard DIY filters built by the small scale fish farmer and the backyard aquaponic enthusiasts, I thought it might be fun to whip up yet another type of swirl filter for those working with a backyard budget and love the DIY of building your own filtration at home.  The following is an explanation of our DIY backyard Budget Swirl Filter or “Dizzy Filter”

DIY Budget Swirl Filter

Let’s first touch on how a swirl filter works, we covered some of this in this swirl filter article. Many may confuse a settling basins with a rotational water flow to swirl filters and the primary difference in the speed at which the water flows through them and that is relevant to their size in comparison to the volume of water they are filtering.

For example, we use what is called a retention time in a filter, be it a swirl, biological or settling basins.  This relates to how long the water takes to flow through the filter.  With settling basins the retention time is generally more than 20 minutes and is also dependent on the area of the basin or tank.  A swirl filter is at the other end of the scale and can have a retention time between 1 minute and down as low as 30 seconds.

The idea behind a settling chamber or basin is to move the water slowly through the filter allowing enough time for the solids to fall out of suspension on their own accord.  The swirl filter on the other hand, like pulling the plug out of a sink, forces the solids out of suspension using the vortex or hydrocyclone action to force the solids to the centre bottom of the filter.

So you can see how very different they are, let’s take a look at a what size the filter vessel would be for a 2000 litre tank for both the settling type filter to the swirl filter:

We will assume the fish tank exchange is once per hour to make the math easier, though often the flow rate is much higher.  With 2000 litres per hour flow rate you divide that by 60 to get minutes and then multiply that by the retention time for each filter type.  A settling basin with a minimum retention time of 20 minutes would need a minimum filter vessel size of 670 litres (2000÷60×20).  A swirl filter on the other hand with a retention time of 1 minute requires a vessel size of only 33 litres and if it was 30 seconds it would be half that at 17 litres!

For the technical members:

The correct or more accurate way of determining the filter vessel size is to apply what is called a hydraulic loading rate in terms of volume of water per square meter of vessel surface area.  In the case of our swirl filter this would be something in the order of 166 litres per minute per m2 but we also have to keep our retention time of say, 1 minute.

In the “Dizzy Filter” we have a 20 litre paint bucket as our swirl vessel and the area of the surface of the bucket is (pi x r2) 0.19m2.  Using the 166 litre per minute hydraulic loading we multiply 166 by 0.19 giving us a maximum loading rate of 31.54 litres per minute.  Because our bucket is only 20 litres this loading rate gives us a 38 second retention time which is between the 30 seconds and 1 minute rule of thumb.

With those results we can say the Dizzy Filter can cope with a maximum flow rate of 31 litres per minute or 1892 litres per hour making it suitable for our 2000 litre fish tank because the volume of the funnel has not been accounted for yet giving us a little more volume in the swirl filter.

If we wanted to put one together for a 1000 litre tank, you may get away with using a 10 litre bucket with a lid and smaller outer drum.

 

DIY Backyard Budget Swirl Filter

The “Dizzy Filter” above is very simple to put together and very inexpensive and will only take an hour or two to put together.  The image above should help you work out what is needed and how to build the filter.

I look forward to seeing your photos of your versions of this DIY Budget Swirl Filter and I hope you have gained some valuable information about design.

Regards
Paul

There are so many ways to build a backyard budget swirl filter and I have seen some fantastic backyard DIY filters built by the small scale fish farmer and the backyard aquaponic enthusiasts, I thought it might be fun to whip up yet another type of swirl filter for those working with a backyard budget and love the DIY of building your own filtration at home.  The following is an explanation of our DIY backyard Budget Swirl Filter or “Dizzy Filter”

DIY Budget Swirl Filter

Let’s first touch on how a swirl filter works, we covered some of this in this swirl filter article. Many may confuse a settling basins with a rotational water flow to swirl filters and the primary difference in the speed at which the water flows through them and that is relevant to their size in comparison to the volume of water they are filtering.

For example, we use what is called a retention time in a filter, be it a swirl, biological or settling basins.  This relates to how long the water takes to flow through the filter.  With settling basins the retention time is generally more than 20 minutes and is also dependent on the area of the basin or tank.  A swirl filter is at the other end of the scale and can have a retention time between 1 minute and down as low as 30 seconds.

The idea behind a settling chamber or basin is to move the water slowly through the filter allowing enough time for the solids to fall out of suspension on their own accord.  The swirl filter on the other hand, like pulling the plug out of a sink, forces the solids out of suspension using the vortex or hydrocyclone action to force the solids to the centre bottom of the filter.

So you can see how very different they are, let’s take a look at a what size the filter vessel would be for a 2000 litre tank for both the settling type filter to the swirl filter:

We will assume the fish tank exchange is once per hour to make the math easier, though often the flow rate is much higher.  With 2000 litres per hour flow rate you divide that by 60 to get minutes and then multiply that by the retention time for each filter type.  A settling basin with a minimum retention time of 20 minutes would need a minimum filter vessel size of 670 litres (2000÷60×20).  A swirl filter on the other hand with a retention time of 1 minute requires a vessel size of only 33 litres and if it was 30 seconds it would be half that at 17 litres!

For the technical members:

The correct or more accurate way of determining the filter vessel size is to apply what is called a hydraulic loading rate in terms of volume of water per square meter of vessel surface area.  In the case of our swirl filter this would be something in the order of 166 litres per minute per m2 but we also have to keep our retention time of say, 1 minute.

In the “Dizzy Filter” we have a 20 litre paint bucket as our swirl vessel and the area of the surface of the bucket is (pi x r2) 0.19m2.  Using the 166 litre per minute hydraulic loading we multiply 166 by 0.19 giving us a maximum loading rate of 31.54 litres per minute.  Because our bucket is only 20 litres this loading rate gives us a 38 second retention time which is between the 30 seconds and 1 minute rule of thumb.

With those results we can say the Dizzy Filter can cope with a maximum flow rate of 31 litres per minute or 1892 litres per hour making it suitable for our 2000 litre fish tank because the volume of the funnel has not been accounted for yet giving us a little more volume in the swirl filter.

If we wanted to put one together for a 1000 litre tank, you may get away with using a 10 litre bucket with a lid and smaller outer drum.

 

DIY Backyard Budget Swirl Filter

The “Dizzy Filter” above is very simple to put together and very inexpensive and will only take an hour or two to put together.  The image above should help you work out what is needed and how to build the filter.

I look forward to seeing your photos of your versions of this DIY Budget Swirl Filter and I hope you have gained some valuable information about design.

Regards
Paul

About the author

Paul Van der Werf

Paul is the Operations Manager for a 4400m2 integrated aquaculture pilot project in the United Arab Emirates desert he designed and built. This is a commercial aquaponics pilot to evaluate integrated farming in arid climates.

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10 Comments on “DIY Backyard Budget Swirl Filter

  1. QwkDrw

    Hey Paul…

    Been racking my gray-matter in an attempt to design the spiral filter which you already have. Glad you had it on AP HQ! Thanx!

    QwkDrw

    1. Try not to bend the grey stuff too much mate. I look forward to some photos of your make of the filter when you get a chance.

      Regards
      Paul

    1. Hi Alan,

      Always good to see modified filter designs out there. Good on you.

      Regards
      Paul

  2. tim

    The interior “bucket,” does that go to the top of the larger container(above the water level)? If so I do not understand the filtration. If it goes above the water level how does the water pass through the filter besides the bottom valve. The dump line valve I am guessing that you can’t open that for an extended time unless you turn off the inlet. I am sorry for this very remedial question I am very new to aquaponics. If you did put a valve at the inlet pipe and turned it off then drained the contents(poop) of the small container?
    tim

    1. Hi Tim,

      The interior bucket simply overflows into the larger drum. So it skims off the top of the little swirl filter (bucket) the clean water. You drain off the collected solids from the bottom small pipe (put a valve on it).

      Regards
      Paul

      1. tim

        Paul, thankyou very much, that is what I thought but just wanted to hear that. Now I am thinking how I could drain the poop without the gushing of water out the dump line. I dont think I am looking at this wrongly but if you open the dump line valve wouldn’t the water come gushing out? I dont know if you have solved this or even if this cleans well as it is, but what if you used an expander from the funnel bottom to a larger and at a 45 degree angle pvc to the outer valve? Or even better what about a collection area under the funnel or bucket with a valve to stop the water all together when you drained it. Yes the collection area would fill up with water but at least it would be more manageable then a stream. But after it filled up would the pressure from the collection area prevent the poop from accumulating in the collection area? Secondly what do you think about a filter box, though I am less thrilled about this because you have to occasionally clean the filters?

        1. Isla Winton

          Hi Tim
          To answer “how I can drain the poop without the gushing of water out the dump line” I would think that you would turn off the pump for a short time and everything would stop flowing and you could then open the pipe into a bucket and collect the poop.

  3. Very good information. I understand the concept of the radial filter and the swirl filter. My problem is the pipe/line from the pump to the intake pipe of the radial. The pump I am looking at has a 1/2″ connection, the problem is these sizes do not match the pvc connections.

    I am stumped.

    Any help would be appreciated.

    1. Hi JMan,

      You should be able to upsize the outlet from the pump with fittings to suit PVC. If not you may need to use poly pipe instead. Though most will convert to PVC. The pump should have a threaded fitting on it. Unscrew it and head to the plumbing shop with it to find a threaded socket to suit the size of the pump and the PVC you want to use.

      Regards
      Paul

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