Backyard Aquaponics
A place to discuss aquaponics

Chappo- I see another problem with your system, if the gravel grow beds are also a direct connection to your DWC- what do you do if the gravel needs cleaning or if you get a leak, how do you fix it without shutting down that whole area? The thing that compelled me to chose aquaponics over other aquaculture systems, was the fact that, with a few shut-off valves strategically placed, I could compartmentalize each area or even a section within an area for repairs. even replacement, expansion or for permentantly rerouting water flow- it gives you infinite control without damaging the bacteria colony and therefore the fish.

As far as the venturi drains are concerned, a lot of people think they operate on syphoning. Technically, that isn't true. A real syphon drains water above the static level of the water- it drains up and over the lip of the tank by using the pull of the water draining to pick up more water. Invariably, true syphons have to be primed- meaning that they need to be filled with water before the action becomes automatic. Any air within the syphon breaks the action and the syphon has to be primed again to restart.
The venturi drain actually operates on gravity feed. If suction is broken by air, the U shape of the fish tank drain and the external stand pipe remains filled with water and will not move until the fish tank water level is again over the lowest drain pipe level. The syphon action is only there as water is viscous to a certain degree and will pull any water from behind, just like a true syphon.

The reason why venturi drains are so popular with aquaculture is for several reasons.
1- when used with an external standpipe, the fish tank is never without water. When fill water is stopped, the water level drains only to, and will remain static, at the lowest drain pipe level.
2- self cleaning action. When combined with a circular tank, you acheive a vortex (downward circular motion toward bottom center- think of a reversed torado) within the tank that pulls fish and feed waste to the bottom quickly so that the drain can suck it up and remove it before it becomes a problem.
3- monitor blockage. If you have a bottom drain (like a shower drain), if it becomes blocked, you won't be able to tell unless the water is overflowing the tank, if you're not there to see the water level rising before then. Also, how do you clean a shower type blocked drain easily? With a venturi drain, if the outer sleeve becomes blocked with say, dead fish, the water level rises but will continue to drain over the top of the outer sleeve but will still drain down the internal drain pipe. If the internal drain pipe becomes to get clogged, you can run a brush down the pipe because it is accessible from the top. Hopefully, you will see the water rising from an internal standpipe blockage before it overflows the tank lip but that could be prevented with an overflow drain installed prior to operation. Everything can be prevented with a good design and operating within the capacity of the system.

Angie,,thanks for feed-back.
The grow beds are phsically beside each otherbut seperated by a brick wall that allows the flood drain on the gravel bed to work. Gravel bed to floating raft , the water mooves between the two by overflow weir and 3 stand pipes.
Any problem in the gravel area and a peice of flexi tube from water "in" pipe layed around bed so water goes directly to the floating raft bed.

One of my first designs incorporated a steel door on one sideof the gravel bed in case of excessive gunk build-up. BUT I have read on here time and time again that this just does NOT happen,so this acess door was removed in the latest plan drawing.

The'shower drain" (gooddescription actually) has a 20 mm holesizedmesh cover that stops anything bigger than 20 mm getting into the pipe,,pipe is 50 mm ,so I can't it blocking very easily.
The advantage of this ,in my opinion , is that the fish poo,as you stated ,is concentrated into the centre bottom of the tank ( especially concentratedif you use a conical bottomed tank, and with this type drain is actually concentrated INTO the beginning of the drain pipe and very quickly removed with a minimum of other water.Thus we could do very short but regular drainings (perhaps taking as little as 20 litres on each cycle).
Drain time and time between cycles is as simple as a timer connected to the electric valve.
This also makes it easy to increase drain time or decrease cycle time when needed,,,e.g feeding times.

That is the beauty of these systems- there is no right or wrong answer, only what works and the creativity in each of us. More power to you.

Thanks Angie ,, and the best thing is....... if it fails I can write about it here and others won't make the same mistake:) . We live, we err , we learn. Sharing here just removes a few errs:)

Venturie drains ,, Shift pistd ,, stand pipe ,, ect ,in the last 2 pages of my thread you will see photos of a new venturie drain i installed and boy is it sucessfull if i ever do a nother fish tank thats what i will use

If you are draining or pumping at the bottom of your fish tank, remember to protect against the fish tank going dry should unforseen failures happen.

Thorn,
That is the beauty of the drain formerly known as "venturi drain" I really must find out what the final verdict was about the new name for those. Anyway, it is essentially an overflow that draws the water from the bottom but can't drain the tank down below a set level. It is either set up like a bell siphon stand pipe but minus the cap on the outer "bell" pipe or it can simply be a pipe that exits out the side of the tank at or below the desired water level where one pipe goes down to the bottom of the tank to pick up the solids and then comes up to the desired water level where a T is put in place instead of an elbow which might cause a siphon. An additional option would be to hook the second method to a no holes overflow but no holes overflows require regular checking to make sure they don't get a bubble that would stop them working.

All those methods work well for removing solids from the bottom of a tank without draining the fish tank below a certain point. I know because I have tested out at least one model of each of those methods. Note One should always take precautions to make sure your fish can't swim into the pipes because they have a real hard time surviving once they are laying on top of your gravel and it is really shocking what a fish can manage to swim through.

So an overflow with a long input, gotcha. Seems easy to keep bubbles out of the input if it is turned face up, although you wouldn't be sucking junk from the VERY bottom then....Could go halfway between the two and have it horizontal at the bottom.

It was named "Solids Removing Overflow" -SRO

Here was the discussion about the naming of the method: viewtopic.php?f=8&t=4127&st=0&sk=t&sd=a&hilit=rename

Here was the voting on naming viewtopic.php?f=8&t=4138&p=149171#p149171