Backyard Aquaponics
A place to discuss aquaponics

OK - I made my first mistake already - the 10,000 litre above ground pool (with food grade liner).
Now's the time to compound my mistake by starting from a level of absolute ignorance

My wonderful employer gave me a bonus of $3,900 and I want to spend it wisely. The pool cost $600 & the roof about $300. New major expenses are going to be the pump and grow beds. Plus I want to go solar, so I think my money will run out.

I built a corrugated steel roof over the pool and its got about 8,000 litres of rain water in it with a few guppies to eat the mozzies. I think I'll stick with 8,000 litres for now, and I'll start with 100 Jade Perch.

I got a quote from Murray for 3 of his grow beds. I'm 95% sure I'll buy those - I can't find anything approaching them that's suitable, although they will be a major expense.

3 beds will be too few to service 8,000 litres. There has been vigorous debate between MF and AA about this

My newbie logical brain tends to agree with MF that the ratio of fish to beds is important to achieve good nutrient concentration to the beds, with good cleaning by the bacteria. But AA has a good story to tell and sounds convincing also. Time will tell.

I plan to get a 10,000 litre/hour pump. Sounds oversized to me, but that was the recommendation from the website & I figure I can throttle it down
by playing with the head & by feeding excess capacity back.

To be continued..

Pumps always sound oversized, don't they ? My first mistake (in this field, made plenty of others elsewhere) was to buy too small a pump. and it's struggling to do the job for me. Go too big and use the excess capacity to aerate you pond - return line with ball valve will give you plenty of control.
My inexperienced opinion only, but the same setup works for hydraulic stuff I've built when using mismatched parts.
TOTAL CONTROL - that's all I want -----

I have a 500 litre header tank - a water butt from Bunnings.
The conservative capacity of Murrays 3 beds is 450 litres of water, so the auto-siphon the the tank needs to kick in and deliver only 450 litres.

The pump will be continuous flow, so the auto-siphon in the header tank needs to extract water faster than the pump is putting it in. The difference between the two rates will dictate how fast the tank empties - and importantly - what capacity to fill the header tank to.

This is getting tricky. I only want 450 litres delivered by the auto-siphon, but the pump is continuously putting in extra water, which will slow down the siphoning process. So the "trigger" volume in the header tank must be a lot less than 450 litres. My head is hurting

Big Mick - what sort of gizmo do I need to split the water? (into the header tank & back to the pool). I am a total ignoramous in this.
a straight "T" piece arrangement seems too "abrupt" - lots of wasted energy?

I also figure on suspending the pump from the roof into the water on an extensible pole so that I can vary the head by lifting it higher or lower. I should get a 50cm range of "head" to play with.

Jamie, come out Sunday and take a look at my system, I am only 10 minutes drive from you. Give me a ring Sunday morning and make a time 07 3200 0272 or house 07 3297 5124

Muzza

Ok, my brain is still hurting. The critical bit of info I need is some data on auto-siphon flow rates. That will dictate the pump flow rate I need into the header tank. Problem number 1.

Second problem:
I am hearing that peoples grow beds are taking a long time to empty? Someone said an hour?

With a potentially high flow rate into the header tank I need an equally high emptying rate from the beds; What goes in must come out at the same rate. I think I need a "high speed" system to ultimately make use of the fish carrying capacity of the 10,000 litre pool.

This suggests to me that I need to ensure the water permeates fast through the medium to the bed exit point.
I would imagine (!) that over time the gravel will get less permeable.

What I am proposing to do is to fill the bottom 15cm of the beds with gravel, and then fill the rest with those hydroponic plant pots that are full of holes, full of gravel.

My thinking is that there will be ample space for water to quickly travel to the exit point in between the pots. The pots will easily fill & drain the nutrient, and I will have the convenience of easily planting & maintaining the bed... ??

Jamie, I will have your book for you possibly tomorrow, once you have "the Book" all will become clear.
I have just sent you an email

Murray

The Book the BOOK!!
Thanks Murray - I think I need it urgently
Thanks for the offer to come round - Sunday sounds great - I'll give you a ring.
Cheers
Jamie

I could easily get out of my depth here, because hydraulic systems run a lot more pressure than we have available here, and there is no 'head' as such, equal pressure in all parts of the system.
Here goes, anyway. I'd be using as large pipe diameter as I could manage, always at least as large as the pump manufacturer specifies because you will get less line resistance or friction and you'll get the best performance from your pump. The larger the pipe, the slower the flow, (10000 lph thru a 12mm pipe is a squirting, blasting, unmanageable torrent, 10000 lph thru a 150 mm pipe is a trickle, if you get my drift). You could put a ball valve in the main line from the pump and use that to control pump output to a certain extent, but try not to throttle the pump back too far - if it sound like it's slowing down it's working too hard - this cuts out seals and makes motors angry.
Then I'd have a tee, still the same pipe diameter, one branch heading for each target, (growbed, header tank, pond, whatever) and a ball valve on each of those - by twiddling the 3 valves you should be able to get your flows right, and once set you shouldn't have to change things too much - until you add another growbed, header tank etc, then you can add another tee, another ball valve, open up the valve on the main line to make up the difference and so it goes---
I can't see the adjustable pump height making too much of a difference, some but not much - I could be real wrong here because I haven't tried it -- open to discussion here.

Big Mick. Good Idea about the larger pipes. The "litres/sec" would be the same but less friction and power?

The max head of this 10,000 lph pump is 3.5 metres. I'll be running it at 2 metres so I guess a flow rate of about 6000 lph. +/- 25cm is a range of 5000 to 6428. So it might be useful for fine tuning. That's assuming the relationship is linear.

Close to linear, I think. Did I see Monya post a pump flow chart recently ?

jamie,I would be interested in seeing some pix of your setup(sounds good)

Yes, Thanks Monya - looks linear enough to me.


Quoting myself

I want 450 litres delivered. What I said above now appears to be nonsense(?). The Radius of the tank is 40cm. Vol = pi x radius squared x height.
So height of siphon must be 89 cm.

AA worked out that with 13mm siphon pipe, the maximum input rate was 500lph and the siphon rate was 770lph.
BIG assumption now:
Assuming my flow rate into header is reduced to 2000lph (4 times AA's), my siphon diameter should be about 52mm.

If this isn't all BS, at an input flow rate of 2000lph, it'll take 13.5 mins for the siphon to kick in. If the outflow rate is (770 x 4) = 3080lph, the effective output rate will be 3080 - 2000 = 1080lph or 25 minutes.

(I'm beginning to think this is garbage. Doesn't look right).

gnash06 - I haven't got anything to look at yet - just the pool & the header tank.
I am trying to work out what I need - its all theoretical.
When I have something worth looking at I'll take some piccies