Backyard Aquaponics
A place to discuss aquaponics

You can build something like in diagram with just a few simple fittings... design it right on paper the first time and you can easily avoid the costs associated with multiple fittings e.g. use box pipe or large bore DWV and uniseals for the distribution manifold instead of narrow pressure PVC and individual GB balancing valves; use a common drain etc.

If you're going to employ a timer, then I don't see any point in using siphons (yeah... they're cool to watch, but they can be troublesome at the most inappropriate times). I only use siphons in CF systems to help prevent still-water pockets which may become anaerobic by changing the water level.

Use an air pump for the FT/ST for the periods when the water pump is off.

Uniseals seem hard to source in Port Lincoln, does anyone use an online supplier they can recommend ?

Thank you !!

A quick penned plan.

A couple of comments...

For the distribution to the GBs, it might be useful to do a search for "common distribution manifold" : a simple way to use gravity and some very simple physics do deliver equal volumes of water to each GB without the need for balancing valves or other technology. Install a drain back to the ST and a removable end cap will come in handy for maintenance and occasional cleaning.

Instead of using multiple DWV90 'T' pieces, I'd be looking at the availability of box pipe, or using the large diameter DWV with uniseals and "small" diameter vertical risers (25mm or smaller PVC works nicely with 90/100mm piping and uniseals, it's possible now to mix DWV, stormwater and pressure PVC!

Add an overflow from the FT back into the drain (or direct back to the ST) allowing the flexibility to isolate all GBs whilst still circulating water from the ST to FT and back again, and as insurance if the SLO gets blocked for any reason.

For the GB drains, have a look for shower drains (40mm); they're compatible with pressure PVC threads and you can then fit your 25mm into that drain using a 25mm PVC reducer (as they do at BYAP -- I've played with many variants and always end up back at the tried and proven method). They also allow for (very close to) complete drainage.

Does anyone have any sources for the distribution manifolds in Australia? I have googled to no avail

You make the CDM yourself, using a large bore pipe located below the lowest GB level and use vertical risers to distribute equivolume amounts of water to each GB. I've posted pics showing the concept here on the forum, a few minutes searching should yield results.

If you get them made they cost a fortune.

You can just make them up yourself.