Backyard Aquaponics
A place to discuss aquaponics

Put two affnan's into use yesterday using 20mm - 15mm reducers and they would start fine but not break as my inflow was to great. Swapped to 25mm - 20mm reducer and tank bulkhead with 50mm bell and it starts great same as yesterday but still won't break. I made two exactly the same and one breaks sometimes.

Thinking now that my gravel screen might not have enough holes as that is the only difference between the two beds - what a pain to remedy. Simo, you got a picture of your screens so I can see how many holes you put in it?

This gives weight to my theory that the 'affnan' siphon aids siphon start. That vortex like reducer means the start is much more likely. I never thought it would do anything to improve siphon break.
Add an air tube to break it and all will be well.

I had an air tube on my last siphon and never liked it. What size tube and fittings do you use for your air breaks? I am going to play around with the system more and see if I can get them breaking without tubes first, more holes in the gravel screen will be my first stop.

The Affnan's definitely start first time every time, no issues there. I only use the one reducing coupling (25mm down to 20mm)and don't reduce to the extent that Simo has (32mm down to 20mm) and it still starts great. Also they don't gurgle so much as a pipe when just used as a standpipe.

Is that the croaking sound they make when they break? I know someone on here had a neighbour that complained about their frogs making to much noise

So the Affnan siphon is a lot quieter? This was something I've taking into consideration when I build my system (timed flood & drain or siphons?) if they are going to be noisey my neighbours will complain
I know if I have trouble whith siphons it's easy to change to stand pipes with timed F&D, but I guess this means changing the pump aswell to a higher rate!?

Also, on one of Affnan's videos on youtube you can hear what sounds like a siphon gurgling away in the background, quite frequently too!! So that one still make a bit noise.

Anyway I'm yet to build an auto siphon , but plan to over the course of this week so I can have a play and I'll of course report back

Here is a top down picture of my screens with my old bell siphon before I switched to affnans, my affnans don't have air break tubes but I see no reason why they wont work with one. I think you might be on the right track with the in flow being too high.

For my screens I used a masonary disk on my angle grinder to cut the vertical slits in 5mm thick 100mm PVC (Sewer pipe) because I found the circular holes would get blocked with the expanded clay pebbles and lots of cuts were quicker then lots of drilled holes.

Also look at your drainage pipes, they should be able to let air back up into the bell to aid stopping and help the bell water drain. Mine drop straight into 90mm pipe so plenty of air can get back up to the bell. No "U" traps with affnans.

Mine are silent when they start and gurgle a little bit when they stop. The noise is a short sharp gurgle not the long multiple gurgles I had using airbreak tubes on bell siphons.

So yes I find them to be a lot quieter.

Guys, the technical term for the noice a siphon makes when it breaks is a 'burp'
Ok, that done, the burp can be quieted by decreasing the flow.
Adding an end cap to the screed pipe around your siphon works well too.
Having a short outflow pipe also helps, as it shortens the burp time.
If I could use siphons everywhere, I would, they're so much more reliable.

I'm thinking the Affnan may be my ticket to siphons across the board.
When I have some spare cash enough to buy a metre of 25mm and 50mm pipe and endcaps, I'll give it a shot.
I suppose I need some downsizers too

My 20mm standpipes drop straight down into 40mm pipe elbows no u trapsso there is no problem with backup. I had another look and I think I have plenty of inflow holes in my screens. I will bypass some flow back into the FT and see if they break by themselves without air tubes. I really don't want air tubes.

Dropped my inflow rate this evening and they both now break by themselves no problems. I have been thinking for a while that siphons operating effectively by themselves is about inflow versus outflow rates. Pipe sizes are important, but only in relation to each other, it is the flow that counts. To test this I will start a new thread and ask people to contribute there inflow versus outflow times and we will see if we can establish a magic ratio for future reference. If this has been documented before could someone please let me know, I could not find it anywhere.

flood and drain times, fill times etc have been documented, not sure where, not sure it's a concise thread either.
but flow rates not so. however flow rates can be extrapolated from bed size and fill/drain times

looks like enough aeration, eh?