Thanks Peter. Where have you used the epoxy putty?

I came up with a new idea for a removable/washable filter system for a BSF unit with at least one wall that is mostly vertical. The filter can be removed for cleaning and also for allowing a stream of water to clear the area between the two pipe sections.

I would also like to test this without the outer perforated pipe and filter for a simplified approach.

After a little more thought about the above concept; I think the outer pipe is all that is needed. The main question I have is how many larvae will exit the waste via the perforations in the pipe section? My biggest concern is that by placing it along the edge of the unit a large number of mature larvae would take these perforations as an exit and drop into the liquid waste. One possible fix for that is to use a whole pipe and place it away from the perimeter of the unit. I have a few ideas about that which I'm considering.

The thing I like about this line of thought is that the drain holes (perforations) on the pipe go from top to bottom of the waste. This way the effluent can find an exit no matter what level it is tending to pool at. In other words; while most drainage systems require the effluent to perk to the very bottom of the waste, this system allows it to drain from higher levels.

Of course this was inspired by PeteB's design early in this thread: Peter's post. The main difference is that I'm being stubborn about wanting to perforate the pipe. I'm not trying to annoy Peter , I just want to see if I can speed up and improve drainage by making holes that the effluent can drain from in the middle levels of the waste.

Hey, I can only comment on stuff I've tried myself. You'll never know for sure unless you make one.

I know, I'll actually build something soon.

One reason it's taking me a while is that I haven't focused on BSF for over a year and it's taking a while to put my thoughts together. For example; I've already scrapped the idea a few posts up for a variation on that theme. Here's the newest version:

Here's the type of fence post I'm referring to for the vertical drain - I chose a square shape to make it easier to attach the drain outlet:

One thing I'm still working on is how to anchor the square drain pipe to the bottom of the unit.

As always, criticism is welcomed.

It occurred to me that a vertical perforated drain pipe might encourage BSFL to eat more in the lower levels of the waste. Any larvae that drop into the drain will be able to crawl back up the inside walls of the drain due to high moisture levels there. They may crawl back through one of the lower perforations which might encourage them to eat at lower levels.

There may be another advantage to this system if larvae drop into the drain pipe and then re-enter the waste. This two-way traffic might help aerate the waste where it needs it the most, if the larvae re-enter at lower levels.

I've almost got the trial version of a vertical drain pipe finished and something occurred to me. If the drain holes became clogged you could collect several thousand juvenile larvae and dump them into the inside of the pipe. I believe the larvae would crawl up and back into the waste through the drain holes therefore helping unclog the drain.

I hope to publish my new experimental design in a few days.

I've posted the new composter design with the experimental vertical drain pipe here: LINK

In my experience, drainage depends largely on the type of feedstock you use. Running four bins this season, I was able to make side-by-side comparisons.
For example, the cow manure is full of coarse particles; these particles build up to form a natural filter which drains beautifully. On the other hand, large amounts of soft fruit turn everything into a swampy mess which is extremely difficult to drain. No two bins are the same, and each one has it’s own dynamics.

On a practical note, I found that crushed leaf-litter improves the drainage. I add a handful or so at every feeding. It’s job is not to absorb moisture, but rather to loosen up the bedding, so the water can get down to the drain. I’m sure coir will do the same thing.

Grub population also plays a role. Five thousand grubs do a huge amount of aerating and tunnelling, whereas a colony of five hundred is barely noticeable.