Backyard Aquaponics
A place to discuss aquaponics

Hi,

Just finished building the greenhouse: 6x4m twin-wall polycarbonate with aluminium framing.

About to start setting up the aquaponics.

Here is a schematic of my proposal:



This is a 4 pump system.

Pump 1: 12V DC cycling off/on every 15 mins to sequence the sequencing valve
Pump 2: 240V AC commercial aquarium filter
Pump 3&4: 12V DC pumps on float switches

All 12V pumps running from a 100AH AGM battery which is charged by a 240V charger.

In the event of a power failure (frequent in my area) the system will still run on 12V until the battery is depleted (should get at least 24 hours). The sump pumps are duplicated in case of pump failure.

The growbeds are flood/drain with no siphon, just a slow drain with standpipe overflow. With the valve sequencing every 15 minutes they will each get 15 minutes flooding followed by 45 minutes draining.

The remaining two outlets on the sequencer are for future growbeds, and at the moment they just flow back into the fish tank.

The fish tank is a 2000L Polymaster with sump drain. The growbeds (plastic 2mx1m) will be filled with Chinese expanded clay balls. The vortex filter has yet to be built but will probably be built from a blue barrel. The sump will double as a fingerling tank and I am yet to decide what to use for that.

And I will be looking at heating the system - I am in the Macedon Ranges, VIC so a cold climate.

Criticism or suggestions welcome!

What's the flow rate for your 12v DC pumps rated at whatever head you might require... typically the height of the intended valve...

I'm concerned that most 12v pumps usually don't have either a high flow rate... or head capability..... probably not sufficient to satisfy the requirements for valve operation....

There is a "low flow" valve stem option that might work....

Also... your vortex filter .. as drawn.. seems to be constantly fed by a bottom drain from the fish tank....

When the timed pumps are off... the water level in the fish tank will equalise.. to a level in the vortex filter...

Which could mean some overflow.... on it's own...

But you'll probably be still/could be pumping from the float activated sump pump...to the fish tank... as the grow bed drain....

Doesn't that suggest a continuing potential overflow of the filter problem????

Just got in from work so tired and had a few beers but why did you put pumps 3 and 4 in parallel rather than series (assuming they are the same pump)?

Correct.



The top of the vortex filter is planned to be at the same elevation as the fish tank - for this very reason. If I use a blue barrel I will set it so the top of the barrel is level with the top of the fish tank, and the bottom of the barrel will actually be lower than the bottom of the fish tank.

Let me put this another way (and you are from OZ). 3 and 4 will be totally inefficient and if one goes out they will do *frack* all. You either run two lines from the sump or put them in series, and I am interested how you will put float switches on them( yes possible but?) . This is only Imho.

Hi Sleepe,

Regarding the pumps in parallel, I'm sorry I haven't drawn the schematic with much detail.

The plan is to have a check valve with each pump, so that if one stops the other won't just start pumping the water around in circles.

If they run off a manifold as depicted, I will make sure the manifold is of sufficient diameter. They are actually submersible pumps, so I may end up just placing them inside the sump so they will each have their own suction "line". As I haven't designed my sump yet I'm still undecided on that.

The reason I wanted them in parallel is that if one blocks with gunk the other will still pump.

Do you think series is a better option? If one fails, will a windmilling or stuck impeller on the failed pump provide much flow impedance?

Oh, and regarding the float switches, I have some of these:



Each pump will have it's own float switch, in case of float switch failure.

Hoping for 1500L/H



Would like to hear more about your low flow option.

That's about what I thought a 12v DC pump might put out... and a standard aquaponics sequencing valve just wont function with that flow rate...


I'll have to check my figures for a "low flow" valve stem configuration.... I have a niggling suspicion that even then the flow rate might be marginal...

The other thing is... with a 1500L/H flow rate.... your two grow beds (allowing for media displacement)... will require about 700L to fill during the timer cycle.....

That would take 30 min to fill the beds at that flow rate... so you wouldn't be able to use a 15 min timer cycle...

It could then take 20-30 mins to drain the 700L back to the sump.. and fish tank.... which probably only gives you half the tank turnover/hour.. that you should have....

Don't think that would be any where near enough for trout... without external aeration... and would probably limit your stocking capacity....

OK, yes you are correct - but I was going to sequence one growbed for 15 mins, then recirc for 15 mins, then the other growbed for 15 mins, then recirc again for 15 mins - hence the 4 way valve. Each growbed gets 45 mins drain time 30 mins out of phase to minimise level changes in the sump/fish tank.

The option then remains to double the number of growbeds using the remaining two sequencer outlets for maximum stocking levels.

But... if the pump won't work with the sequencer then I'll either have to get a bigger pump or go back to my original plan of one small pump per growbed.

Ideally you should run two sets of pipes one for each pump (providing they can make decent flow at head).
If you can have only one pipe I would put them inline ie series.
I have only seen two brushless centrifugal pumps stopped by obstruction, one was a Davey sump pump I was given because it was 'broken', it wasn't it had gravel stuck in it and the thermal overload had tripped. The second was my own fault when the screen fell off my pump and a huge mass of tomatoe root went through it again the thermal overload tripped. What most people think of as gunk stopping their pump is actually the cap failing or failed.

Thanks Sleepe, I'll keep that in mind. Much appreciated.