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Building a medium sized flow-through system in South Africa

January 6, 2009

Hi All

We moved into a new house recently and the previous owner graciously left us some wooden railway sleepers (270x120x2100mm = 10.6"x4.7"x6'10.6"), that had been used as a water-feature. Not being a huge fan of water-features, but a large fan of earthworms I decided to use sleepers to build a worm bin. After some research I found splitsec002's message which gave me lots of ideas.

Here is my design so far. Obviously I still have to build and test it to see how well the various bits hold up. I'll update with more pictures are the build progresses.

Top View

Scraper Detail


PS: I don't think the treated wood will harm the worms too much since they live quite happily under it at the moment.



Comments (29)

  • eric30

    Instead of threaded rod I would recommend using lengths of conduit. You'll save a load of money and it is still rigid enough to hold the weight. Good luck, it's an exciting project.

  • pyropunk

    By "conduit" do you mean 5/8" galvanized pipe or something similar? Do you think 1m (about 3') lengths will hold the weight. Internal measurements are 1x1.6x0.6m = +-3'x5'x2' which means the full bin will contain about 1cubic metre of compost which will weigh about 1 ton!! And how do I make it stay in place? Actually I have already bought the threaded rods - and they were quite expensive. Thanks for the tip though. I just hope my "protected scraper" idea will work.

    BTW the images above are much larger you can save them and view them in your favourite image viewer.

  • pyropunk

    Quick update:

    Destruction of the water feature

    The black fiberglass tray/tub on the right will become the VC catcher.

    Layout of the worm bin

    I'm leaving a small gap between the ground and the wood for air and to prevent (to some extent) termites.

  • leearnold

    Just a note, pyropunk: The wooden railroad ties are treated and shouldn't harber termites. However, the wooden siding on your house ISN'T treated. I wouldn't put this directly up against the house if I were you. You are just asking for trouble with the moisture and all....

  • pyropunk

    The railroad ties should not harbor termites, but they have been outside quite a while and some of the treatment is probably no longer protecting the wood.

    It's not against the house. The wall you see is a pre-cast cement garden wall.

  • pyropunk

    Ok, update time again.

    I finished the basic bin without the scraper mechanism today.
    This first picture shows all the railroad ties/sleepers have been sawn to size and gives an idea how the tray is going to fit. I found some (21) flat roof tiles which I used as a floor.

    Here the frame that is holding the rods is already in place. After thinking about my design for the bolts through the rectangular bar, I realised that the heads are going to be in the way and I decided to just cut out a section and sink the bolts inside the bar.

    All rods have been fitted and some gaps have been filled with PolyUrethane (PU) foam. The IBR sheet on top are actually two pieces which I have already pop-riveted together for a lid.

    Lessons learned:
    1) Even though PU foam expands it still takes a lot (about 4 cans) for a project this size.
    2) Because I fitted the frame first and did not want to remove it and redo it, I had to bend the rods to put them in. Would probably have been quicker to take everything out, fit the rods outside and then put everything in.
    3) IBR sheet looks light but is damn heavy. I have to make a plan so I can lift that lid and keep it open for feeding time.

    Next step:
    Build and test scraper mechanism.
    Finish lid.


  • pyropunk

    oops. the second picture should have been this one:

  • eric30

    Wow, quite the project. Please keep us updated on your scraper mechanism! Eric

  • pyropunk

    Parts list so far.

    Bin itself:
    18 x railroad sleepers/ties (12x25x210cm) - free
    1 x fiberglass bin/tray (90x162cm - 30cm deep) - free
    21 x flat roof tiles - free
    4 x bricks - free
    4 x 750ml PU foam

    Frame and grid:
    3,24m (2 x 1.62m) L bar 35x35mm 5mm thick
    2m (2 x 1m) rectangular tube 25x50mm 1mm thick
    53 x 1m threaded rod 10mm
    96 x (53x2-10) nuts
    16 x coach bolt 10mm
    6 x square washer 20x20mm 3mm thick

    2 x 2m IBR sheet
    2 x 1,51m wood 10x50mm
    18 x pop-rivets
    6 x wood screws
    I still need to fix/hinge the lid at the back and add a stay in front to keep it open during feeding.

    Still needs to be built, but I have so far:
    2 x 1,5m threaded rod 10mm
    20 x nuts (just a guess as to how many I need)
    2 x bicycle cog
    2m bicycle chain
    1,62m L bar 35x35mm 5mm thick
    1m 2" PVC pipe - will be cut in half - I just realised this will not work - will have to rethink the design!
    some length of rod (+- 27cm) for the handle
    some round tube (+- 12cm) for the handle
    a couple (4 or 6) of washers

    shovel/spade to level the ground
    measuring tape
    spirit level
    circular saw
    hand saw - wood - for the bit the circular saw did not reach
    grinder with a thin blade/hand saw - metal
    metal file
    G clamps - since I don't have a vice
    - 10mm metal bit
    - 8mm wood bit
    - 4mm stubby bit for rivets
    - 3mm stubby bit for screwing wood to IBR
    - 12mm long wood drill - for the scraper
    welding machine with all paraphernalia - unused for now

  • pyropunk

    Update time again.

    Worm relocation is complete! They are now in witness protection and I hope they never have to testify as to the anaerobic conditions in the plastic bins ;-)

    After a lot of thinking I have decided to keep it simple and scrap the whole scraper idea (if you pardon the pun). Especially since I expect to be harvesting in only about a years time. I think I'll be able to use my rake where the tines are just far enough apart to get in between the rods and remove the VC.

    To the pictures:

    Lining the grid with newspaper. I took Eric's warning about fall-throughs to heart and made sure that the newspaper touches the walls properly.

    A (not so clear) view from the underside before adding the bedding and worms. Some PU foam is visible where I have filled the gap between the frame and the railway sleepers.

    Filled the bin with some compost that was lying on my roof and filling up the drain pipes as well as some other chipped branches from the garden. Then I added the contents of one worm bin. It's amazing how it disappears in the huge bin.

    One happy occupant disappearing into the leafy bedding.

    Both plastic bins have been transferred. The anaerobic conditions in there were quite horrible. With both bins added there is still almost no increase in volume.

    Relocation complete. The black bins on the left were the original "homes". There is a gap between the lid and the bin itself. I'm still thinking of whether and how I'm going to to prevent some of the more unwanted (less wanted?) critters to enter through there. Maybe some kind of net or burlap. For now the original worm-compost is covered with more of the "roof compost".

    The added weight has compressed the soil underneath and now the tray does not fit any more! Now I have to take out the tiles, scoop out the soil by about 1cm and put everything back in again.

    Thanks for reading, it's been fun!

  • eric30

    Hey that looks great! You may reconsider the use of the tub. The bin will probably continue to sink into the ground over time. Can you go without it or use it for a container garden? I like the idea of using the rake to harvest, the simpler the better right?

  • leearnold

    Wow! That is one great looking bin! Looks like you put quite a bit of thought (and work) into this one. This should work to process LOTS of organic matter.
    As for the catch bin not fitting - could you simply hoist each end and put another sleeper underneath each end. That would raise it up even more so that IF it does continue to sink some, you would have a little extra room for compression. Or is it to fragile/heavy to lift?
    You shouldn't have to worry about critters coming from the bottom into the bin as long as it is covered with compost, however, coming in through the top MAY be a problem. If you're talking about fungus gnats, spring-tails, mites, etc. a cloth cover would help keep them out. If you're talking other animals (mice, rats, raccoons, etc.) I'm not sure there....

  • pyropunk

    Hi all

    Played gardener today since I needed to be at home. Also finished the last lid bits and took some more pictures.

    The grid is holding up nicely. The rods are taking the weight and are all taut and not wobbly like before.

    Screwed two brackets (made by cutting a 20cm piece of rect tube) on the back sleeper using 6 (3x2) 4x60mm wood screws. This is to keep the lid from sliding off when opening it. Here is the RHS one. I made the bracket a bit longer, should I decide to move the piece of wood in a little.

    Used two extra threaded rods as lid stays so I can dig around in there when feeding. They fit neatly into the holes in the sleeper and when holding the lid, are at a slight angle against the wood of the lid. Sorry about the bad quality of the picture - my hand was shaking from too low blood sugar.

    Eric, as to the tray, I was really hoping to fit it underneath, then I can take it out to use it for anything - and not have stand around in the garden, looking ugly. At the moment it is storing the shredded (I bought a wood-shredder recently) leaves and twigs that I cut from the garden today. Man, the crushed Camphor leaves smell lovely (I don't care if its a noxious weed). I still need to drop the floor and then everything is done and I'll leave the worms to do their work.

    Lee, thanks for the thumbs-up. Raising the bin with another sleeper is NOT an option. 1) sleepers are DAMN heavy. My best guess is around 50kg. That means the whole bin weighs around 900kg (18x50kg) plus all the compost weight... and besides 2) I don't have any more sleepers :-( I'm not too worried about mammals. We don't have anything bigger than rats around here, but I'll still make sure that I bury the food properly. That should keep most things away. I have not seen any flies around since I buried all the original, anaerobic compost.

    Thanks for all the comments.

  • pyropunk

    It's FINISHED!

    So I finally finished my "big" project! I scooped out about 4cm of soil under the bin. I hope it does not subside any further.

    Here are the latest pictures:

    Front view with lid closed with the tray in its rightful place.

    Front view with lid open.

    Side view with lid closed.

    So I was digging around in my bin just to check on the general health and found that I also (like Eric) have some heat issues. It does not seem to be very hot, but there is a definite warmth and some steam rising in the early morning. There seem to be some earthworms in the warm parts though and therefore I'm not too concerned right now.

    Also this morning when I wanted to feed I noticed that something had scratched open Tuesday's feeding spot. I suspect a rat. Maybe I'll set a trap. I feed every day since I don't have enough space in my freezer to collect all the kitchen waste that we produce. I have calculated that It will take 42 feeds to come to position 1 again. That should give the worms enough time reduce the last feed at that spot.

    That's for now. Have to practice restraint before I get too obsessed.

    Thanks for reading.

  • eric30

    Looks like you are all set, now the waiting game begins. I'm working on giving my bin thinner layers of food and bedding more often to cut down on the heat produced. They seem to be much more productive this way too. Today it was veggie pulp from the juicer, a sprinkle of stale wheat flour, torn junk mail, paper plates, napkins, a handful of soil, then wet it down with the spray bottle. Mmm, yum. They should have that wiped out and ready for another round in about 5 days.

  • pyropunk

    Quick update

    1) Compost volume has reduced by about 1/4.
    2) Rat is still around. Trying to close all the holes as best I can.
    3) had to excavate the right side even further due to more sinking during the rains.
    4) used some nylon rope to build a handle for the tray.
    5) added about 10litres of water last Saturday and again this Saturday because the compost on top seemed a bit dry.

  • folly_grows

    Pyropunk: That is a thing of beauty. :-)

  • pyropunk

    Weekly update time again

    1) I think I have (partially) resolved my rat problem. I have closed all the holes with steel wool and PU foam. At first she tried to nibble through the PU but I think the steel was hurting her teeth. The "partially" is because I think she has now taken up residence in my ceiling :(
    2) watered again this morning because the newspaper on the grid felt very dry.
    3) I have put some newspaper on top of the compost to keep the moisture in.

    1) Compost volume is still reducing, somewhat slower than before though.
    2) sinking of the bin itself has halted as far as I can tell.
    3) Now that all the holes are plugged there is some condensation on the lid.
    4) The worms are coming to the surface. When I peel back the newspaper I can see a lot of them.
    5) I can find cocoons without looking too hard. Hopefully I'll have a population explosion in a couple of weeks.
    6) When digging around I notice that the worms are rarely deeper than 12cm (5"). Maybe they will move lower over time.
    7) I have some fly larvae in the transferred compost. They seem to be very happy and hopefully I won't have a fly problem later.
    8) Worms seem to be happy and are getting fatter.

    That's it for now.

  • pyropunk

    One month (4 weeks) update

    The rat is gone. The dog killed it, hurray (and eew). I don't even have to search for cocoons any more. I just peel back the newspaper and there they are. Bin still seems healthy and worms seem to be happy.

    Noticed some critters in the bin:
    1) pillbugs/roly-polys/woodlice/Porcellio scaber Don't know the exact species.
    2) mites - have come and gone as far as I can tell. I have seen them "attack" an earthworm but probably only because it was hurt. And I have seen them "attack" a small beetle.
    3) 1 small black beetle - don't know what species
    4) 2 rove beetles
    5) 1 millipede - I killed it
    6) some fly larvae - no idea what species they belong to but they look like BSF.

  • pyropunk

    Another update.

    Just to clarify:
    I do not surface-feed; I bury the food at 2 litre (+-2 quarts) ice-cream container sized locations. As mentioned earlier, I worked out that I needed to feed 42 (6x7) times before I got around to the first location again. It turns out that I sometimes have more food than 2 quarts, in which case I feed two (or even 3) locations at the same time.

    So last week the feeding "wrapped around". The food in spot 1,1 is completely gone except for the corn cobs. There are lots of cocoons, some (about 20) of which I moved to the side to see how they mature. I really would like to see and hopefully photograph a "birth".

    I also can't wait until all the cocoons have hatched so I can start processing my crass clippings.

    Some other critters that have taken up residence:
    1) mites - are still around but not in huge numbers
    2) spiders
    3) a small caterpillar
    4) a single ant

    The rat is definitely history. I left the bin open to dry it out a little and the next morning the newspaper on top was completely undisturbed.

    That's it for now.

  • leearnold

    Alex, I'm sorry you have crass clippings! :) Thanks for the update on this. It looks like a great bin. Have you harvested anything from it yet?

  • pyropunk


    LOL, that should have been "grass clippings". The spell checker doesn't catch everything!

    The bin has only been going for about 6 weeks. I added a lot of pre-composted leaves to the bin and I only expect to start harvesting in Feb next year. For now I'd be happy if the cocoons hatch so that I can slowly start to add the grass.

  • jaybun10

    how did the scraper finally work, could you give us more detail? thanks.

  • 11otis


    that's a very heavy duty bin you've built there. I'm sure it will last almost forever.
    Nice job Alex. And I appreciate the pictures.


  • pyropunk


    I abandoned the scraper idea due to various factors. If I ever build another bin I may introduce the scraper mechanism again.


    I'm hoping that it lasts long. I just hope that the termites don't eat it ;-)


  • pyropunk

    2 month update

    The worms are still happy. Lots of juveniles have hatched. The newspaper at the bottom is starting to disintegrate. I'm still feeding a location a day and I bury the food. It seems to disappear faster that way.

  • pyropunk

    3 month update

    I have stopped burying the food after the second round of positional feeding. The first this I noticed is that the fruit gnats started invading again, after almost 3 months of absence. Also, as the food started decomposing small springtail like insects started covering the food. I do not know whether they are spingtails. They are quite small (about 1-2mm in length) and very thin. And they jump around a lot.

    Also I added some lawn "mowings" to the bin two weeks ago. I spread it over the top as thinly as I could. Some pockets however still heated up, but not enough to cause harm to the worms.

    I filled the bottom trays in the two dustbins with compost and worms from the flow-through and donated one to a friend. Hooray, my first vermicomposting convert. The other bin I put in the garage added one banana peel and I hope to donate that one to the school.

    That's it for now.

  • KeithBenitez_Yahoo_Com

    Just found this forum. I just recently got into vermicomposting. Any updates on your system?

  • trivedi_south

    Any news on your bin/worms/compost Alex.

    I always wondered what happened to the bedding (shredded newspaper/cardboard etc) once it disintegrated.

    Thanks. Awesome job!!

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