Backyard Aquaponics
A place to discuss aquaponics

"kind of just happening to fall into"

is that the birthing method Mrs G is utilizing?

hope all goes well with the new addition.

looking forward to the pics.

Of the mixed cell raceway when I get around to it or the newin

If you say that the solids get sucked into the drain it tends to imply that the force that is driving them into the drain is the suction of the drain. Whereas in fact it is the currents in the tank that concentrates the solids near the center and when water exits through the drain it just happens to contain an amount of the solids that just happen to be suspended in the water when it goes into the drain.

In fact these tank designs don't tend to work so well without fish in them. Without fish the solids (from the absent fish) tend to collect on the floor of the tank albeit near the center. When the fish resuspend the solids as they swim past and the solids move a little closer to the center until they eventually get into the drain.

Yes I know what you mean now. I was still thinking of the water being sucked into the drain to be causing the flow in the tank, but it's not, well it must have some effect but no where near the amount that would have to be to move particles in the water.

I just had another understanding why it's better to have the drain, SLO going up the centre of the of the tank... If it is running across the bottom and up the side it will disrupt the flow around the sides causing eddies and low pressure zones where heavier solids will accumulate, there fore never getting to "fall" into the drainage area.

Cheers.
I just learned something

ok I got a question for you all here... im not to familiar with SLO and bottom drained systems.. from my read here it seems that bottom drain are very effective in removing solids . but im afraid of leaking problems especially if you plan on burying your fish tank.

I'm drawn towards SLO simple because of overflow effect. which basically safe guards the water level constantly within the FT.. my question is for a 2000 gal FT dimensions @ 10ft diameter X 4ft depth. what will be:

1. the idea pipesize to effectively removed solids without fear of settling out..

2. flowrates rates of water into the FT.

3. the water velocity of the swirl within the fish tank.

im forcusing on the overflow design that draws water upwards and overflow at the top of the fish tank with a T fitting to prevent siphoning.. thanks in advance for your advices..

I was paranoid with the whole leaking once buried thing. Seemed like a point of failure that I couldn't diagnoise, let alone fix without a jackhammer. So my whole underground pipe work is buried in a stack of concrete (along the lenght of the pipes). It should take away any issues.

Also, I'd dig a deeper than needed trench for the underground pipes to fit into. And the tank height can be controlled by a stand pipe in the next tank (sump?) it flows into it.

But I think that's why Ryan recommended the bulkhead fitting, they won't pop out easily.

I'm spitballing, because it's what I do.

Earlier in this thread, it was pointed out that the pro tanks can have two drains in them. One bottom center drain, the other in the middle wall somewhere, and it allows you to put the bottom drain through more filtration, and saves on power, etc.

Would it work to have a split system, so the bottom drain is directed to a media bed(s), and the middle drains are directed to a line of DWC beds?

Would the solids (I know that it depends on flow/tank size/etc, but assuming it's in a large tank), settle enough to give good polished water for the DWC? OR would it still suck up enough solids that would cause issues with root clogging?

Hi Colum

I am going to ruin your day for you because as a Yorkshire man that is what I do.

Stuart will be able to add more but I would most certainly filter the water from the middle wall drains. Fish stir the tank up and that will move around depending on your tank currents. It would just require less filtration than the bottom drain would.

Hope that helps.

Stupid fish ruin everything!

They do at that. Take my trout, they refuse to move to the other tank so my new batch coming soon can have the front tank. Can you believe that, as now I will have to net them out.

Quote from Timmons:



I don't know whether 1.5mg/L TSS would require further treatment before being passed to DWC or not

It may not. I suspect not but even if it did it wouldn't need much. A separate small GB would probably do the job or a screen filter. A RFF would have to be huge (relatively to the one used to process the flow form the center drain) to deal with the flow. A screen filter could allow water to flow through quite freely with a bit of maintenance to keep it clear. A GB would still have to be a reaonable size but that size would probably be quite small. If for a 10m3 FT you would need 20m3 of gravel then the DWC filter bed could be 1/14th of this whereas the bottom drain GB could be 13/14ths. Or 1.43m3 for the DWC and the balance for the bottom drain.

Finally getting those photos up I promised.



Couldn't resist.

This is not a great shot but it does show most of the foot on the centre drain. What is not shown is the clear plastic rim (cut from a juice bottle) that extends the diameter of the foot. The photo also shows a bunch of mistakes I've made.

Hard to see but you can see ribs and folds in the liner. These obstacles interfere with the movement of the solids towards the centre drain. Still works but not ideal.

You can also see a fair few white bits of crud in the water. These are fragments of the inner membrane of eggs. I just threw a whole stack of egg shells in my GBs near the outlets. As the egg shells have broken down the membranes became detached and they have ended up in the sump and then gone through the pump. The damm stuff just seems to float around and doesn't settle to get sucked out the drain. Embarrassing and annoying

Thanks for the amazing advice re drainage Stuart

I have just purchased a FT and had a center drain added (2")
Can i ask another question. I saw a link suggesting 20% water to leave the through the center drain and 80% via an overflow which would be enough to encourage self cleaning properties and not have a whirlpool effect.

My question relates to the height of the exits of these 2 pipes.
Should the bottom drain and the overflow pipes return water to the sump tank from the same height?
Or should one be above the other?

Lastly ow is the 20/80% ratio achieved?

Thanks in advance
J

20/80 would be fine under certain circumstances but under others you could go as far as 5/95.

The way you get the difference is by a difference between the ease of flow between the two drains.

The smaller bottom drain comes out and under and then up as in your picture but there is no reason why it cant go higher than the side drain pipe if that is what is required to reduce the flow to the proper proportion. This is often done by means of an adjustable standpipe.

Alternatively an adjustable valve would do that the job.