Backyard Aquaponics
A place to discuss aquaponics

If you can, try to let the pump have some off time during the day, this lets anything that gets stuck to the screen float away.

Dont worry about offending anyone, you will see the error of your ways

Well, my first AP system is almost ready to start working. All I have left to do fill the GBs with media, and finish my drainage system.

I'll post some photos tomorrow, when there's a bit of light left.

In regards tot he GB media, I guess I'll use blue metal like Les or "salt and pepper" like Derek. Whichever is cheaper I suspect, as I can't separate them any other way in regards to pros or cons. Naturally, I plan to give it a wash before putting in my GBs.

I'm undecided about my drainage, in particular the standpipes. As my 2000L/h pump isn't pumping water at a very high rate, I'm considering a siphon setup. I'm having a bit of trouble getting a prototype working in a bucket. I'm trying to use a 20mm standpipe, with a 50mm shroud? pipe around it. Unfortunately, the water stops draining as soon as the level drops to the top of the standpipe. I expected it to continue to drain until it reached the inlet holes.

Any idea what I'm doing wrong? Diagram to come.

It seems to me that the usual water to GB ratio is much closer to 1:1 than 1:2. People that run big sumps really have a bigger tank just in two places. If you have have a thousand liter tank and 2000L GB then you need a 1000L sump therefore 2000L of water, 1000 in the tank and 1000 in the GB's or sump. The only way you can increase the ratio is if you fill GB's in series.

Below is a diagram of the (faulty) test siphon I tried. I fear I'm missing some fundamental concept...

So the water rises above the top cap and starts to siphon the water out, then stops - is that what you are saying Ryan?

Is the shroud on the bottom of the GB and the water gets sucked in through the 8 holes?

I've only tried this setup in a bucket so far. When filling the bucket, the water starts to drain when it reaches the top of the drain. I then remove the hose filling the bucket, and the water drains for a little while then stops also when it reaches the top of the drain.

Yep, the shroud is on the bottom of the bucket and water is sucked through the 8 holes.

Me thinks the holes are not large enough

Really? I would have cut crenellations, but couldn't find my jigsaw. I'll have another crack tomorrow.

Also, the drain pipe is just coming straight out of the bottom of the bucket - is that all I need to do?

les has gone to great lengths in a post somewhere (did we sticky it?) covering outer pipe Vs inner pipe Vs flow rate applicable. regarding these siphons. use the force, luke, err, Ryan.

yep, spent some time reading it, but must be tired, because it all started to get a bit fuzzy

hopefully Les will be able to set me straight.

dont ask me, i didn't read it, crazy old man that he is!

I daresay your pump is quite powerfull TCL, normal little pond pumps for systems of this size do not have the capability of sucking up fish, unless you leave the cover off the impellor

8 holes is enough (just), but if one got blocked then not enough water would flow through the other 7 holes...re-reading it, do you have a U-bend to trap air in the down pipe...from your description it just seems like the water is getting to the top of the drain pipe and then just flowing down and out.

The other area of concern is the height from the top of the drain pipe to the bottom of the bell housing on the shroud pipe...I tried to keep the cross sectional area of this height so that it was slightly larger than the area of the 20mm pipe

e.g.
inner pipe used is 20mm - cross sectional area = 314mm2
height between inner pipe to bottom of bell housing is 20mm =1,256mm2.

this is equivalent of having two vertical 20mm pipes and then having a horizontal pipe joining the two pipes to form the siphon of 40mm...very difficult to make it work because the water needs to rise 40mm above the top of the inner pipe
...................................................................

The height should be around 5mm...this is the beauty of the bell siphon, the water only needs to rise 5mm to cover the pipes to get the siphon working for a 20mm inner pipe...the example above needs the water to rise 40mm to get the siphon kicking in...so check you heights too

good one OBO

I got my siphon working in my test bucket, after putting a loop at the bottom of the drain.

I've now transferred the same config to my blue drum, but the siphon doesn't want to kick in at the intended flow rate. The water rises above the cap of the shroud and nothing happens, until eventually the drum overflows.

When I tried this config with much faster water flow, it kicked in just before the drum overflowed.

Is my drain pipe/shroud too high?