Backyard Aquaponics
A place to discuss aquaponics

Hi Jamie - i know you want to do it all now and I understand this, but take it easy. First - go to Murrays, that is an excellent offer.

You are subject to information overload and a day gazing at veg and talking to Murray will help a great deal.

Also, there is nothing that says you cant have an overflow from your header tank to your fish so it doesn't matter if your pump outpaces the siphon.

As for header tanks, I fail to see the practicality, so here's where I get TOLD again. But really, why?

Go see Murray!

AA - I think we think alike too much and that's the problem. We are essentially saying the same things. Jamie... go see Murray! hehe

Jamie, I agree with AA, MF and all the others, go see Murray's setup, read the book and take it easy. (and keep ansking questions)

There is another thread (still in the theory stage) on solenoid valves, smart relays and water sensors which, if you went the tank header way, would mean cutting off the outlet until the header tank is full - you can then have the inflow less than the outflow and the inflow continuous.

http://www.backyardaquaponics.com/forum ... .php?t=568

Has the website been down or has my PC been playing up?
Anyway - Advice taken - I will go and see Murray!
Tomorrow I plan a series of experiments with different lengths & diameters of siphons. (The equations on the net are too complicated).
Hopefully I can get some valuable data..

Just ordered my Laguna Maxflow 9000 pump (9000 lph) & hopefully pick up the Book from Murray on Sunday

No the site was down overnight (in USA) must've been maintenence

Did some siphon experiments today.
First got some bits - bucket, icecream container, 4, 15,25mm tube:
http://www.backyardaquaponics.com/forum/album_showpage.php?pic_id=188

Then made the siphon:
http://www.backyardaquaponics.com/forum/album_showpage.php?pic_id=189

Siphon in action:
http://www.backyardaquaponics.com/forum/album_showpage.php?pic_id=190

Diagrammatic view:
http://www.backyardaquaponics.com/forum/album_showpage.php?pic_id=187

Conclusions:

1) The length of the siphon below the tank "A" affects the average flow rate. This was significant with a 4mm tube but may be negligible with a faster flowing system.

2) The reduction in flow rate was only experienced once the head fell below the siphon top. Therefore for maximum flow rate, the siphon height "B" should be as short as possible.

3) Combining points 1 & 2 we can conclude that to achieve the highest possible flow rate, the height of water above the siphon should be significantly larger than “B” and that “A” should be significantly larger than “B”. (These points may be of no significance in an aquaponics application).

4) Increasing the cross sectional area of the tube 14 times (4 to 15mm) increased the flow rate by 24 times. The flow rate is dependant on the cross sectional area (given by pi*radius squared). Because the radius is squared, an increase in siphon diameter gives a much larger increase in cross sectional area – ie a higher than expected flow.

The 15mm tube gave a flow rate of 1459lph

For example – doubling my 15mm siphon to 30mm will increase the flow by much more than 2x 1459 lph

Where is this taking me?
With a continuous flow into a header tank, the siphon needs to flow faster (so that it eventually stops!). To get a reliable auto-siphon effect, the difference in flows must be enough to allow a good suck in of air to stop the siphon action.

Additional experiment - use hose to create a continuous flow
Using the 15mm tube setup I ran the hose at different flow rates to see what happened.
At a flow rate of around 450lph the siphon was autocycling reliably.
At around 800lph it was stuck-on - continuous flow. I think that even though the siphon flow rate was 1459lph the turbulance created by the hose was sufficient to keep the water flowing.
So - in this particular experiment - the inflow needed to be about a third of the siphon flow.


Next experiment:
When my pump arrives, plumb in a 30mm siphon into my header tank to deliver a siphon flow of at least 2 x 1459 ie 3000 lph. Arrange to get a continuous inflow at about 2000 lph. See what happens.

I need the auto-siphon to deliver 450 litres per "flood". At 3000lph that will take 9 minutes.
In 9 minutes the pump will have delivered into the header tank 300 litres.
Therefore the siphon needs to kick-in at 450-300 = 150 litres.
The diameter of the header tank is 80cm.
Vol = pi x radius(squared) X height (of siphon)
Therefore height of siphon = 150x 1000 /(pi X 40x40) cm = 30cm

Lets work it through with a siphon of 30cm:
Starting from an empty tank:
The 2000lph pump will put in 150 litres in 4.5 minutes.
The siphon will kick in.
The siphon will remove that 150 litres in 3 minutes, meanwhile the pump has added an additional 100 litres.
The siphon will remove that 100 litres in 2 minutes.
Meanwhile the pump has added another 67 litres.
In just over a minute, the siphon stops.

A total of 300 litres in 6 minutes!!! Not the required 450 litres.

Without boring anybody any more
The theoretical siphon height needs to be 39 cm!!

and increasing the pipe to 40mm gives approx 6,000lph



I'm gonna do a quick edit cause that didn't come out the way I meant it:
Jamie, some of this has been covered here
http://www.backyardaquaponics.com/forum ... c&start=15

40mm drain pipe was used and calculated at 6,000lph, so your figures are matching that - this is good, keep it up because the more individual inputs just make for a better system

Les

LKB - I actually read that thread previously - Great work!
The problem is that there is so much good stuff on this site that you can't find it amongs the chat. In this case I moved on to read some other great threads and "lost" the 40mm = 6000lph bit.

So you are using a header tank with an auto-siphon and its 100% reliable?

Cheers
Jamie

No mate - just have the fish tank and 2 grow beds, what I didn't do was use smaller pipe size, if I had larger grow beds then I would need to increase the pump flow to each bed or decrease the pipe size (as you are testing).

Each grow bed is being fed @ approx 400lph and the siphon/drain has not missed a beat - been running constantly for over a month now, some of the tests I did was to actually remove the siphon pipe and let it overflow naturally, placed the pipe back on and away it went.

Starting to piece together a larger system att but people like MF are trying their best to convert my 60,000l inground pool to AP but naturally I am fighting this urge.

60,000l - sounds cool - but you'd need acres of grow beds
Great to hear the siphons are working. I want to keep things as low tech as possible and siphons are great(if 100% reliable)
So how many fish have you got and what's the tank size?

Cheers
jamie

Dont fight the urge - you will feel so much better when you just give in

Just my little starter system, tank is only 200l and 10 small (but growing) goldfish

AM - have a copper ionizer and the damn walls are impregnated with CU, been measuring the ute to fit that 2,000l monster on

Dont feel ashamed of a small system - looking at the various systems has me wanting to make a 200L system myself - I have the pond, now I need the financial managers of our household's permission

AM - I love it, the amount of experience and knowledge I gained from it is remarkable, I know others have a different slant on small(ish) systems but at that size it is very easy to test, pull apart and reconfigure, from it I have gained the confidence to go larger

First picture - Just beginning.