Backyard Aquaponics
A place to discuss aquaponics

Chift pist - constant height in fish tank pump in sump tank

Pump water from sump to fishtank
Water OVERFLOWS into growbeds via GRAVITY
Growbeds drain into sump

Fishtank always remain at set height

Flood and drain - fill/underfill/overfill up growbed (may take 2 mins or 20 mins) via pump from sump to fishtank. turn off pump to allow drain cycle via 1 or 2 holes in base of standpipe. We talk about 15/45 cycles as this is a common timer found at bunnings. Sump needs to be big enough to take all of the draining growbed water.

Constant flow - pump continuously from sump to fishtank to growbed. Water level in fishtank, sump and growbeds are constant. Water from growbeds drain via standpipe.

Siphon - commonly modeled on affnan siphon. Usually constant flood powered by constant pumping. Will cause growbeds to drain very quickly. So sump needs to be able to hold all drained growbed water.

There are numerous graphs, Tclynx graphs come to mind. Tclynx has also posted a PowerPoint course.

Apologies if I have this wrong, but it seems that you are running continuous flow, not constant flood.
Constant flood (in this context) does not involve siphons, just a standpipe and gravel guard. The GB's are flooded constantly.

Thanks JT and vlt...

vlt, to my understanding anything that drains from one vessel to another by way of gravity is a siphon system. I know the term "siphon" is used here to describe the piece of PVC pipe used to drain a GB, but really a siphon is an action or a function, moreso than a device. Once the siphon, or overflow, has started, gravity will continue to draw (water) until the vessel is empty, unless a siphon break is incorporated into the pipe at a particular level, thus terminating flow.

So, with that in mind, I still can't get around the idea that there must need to be some fluctuation in the level of the FT for this to work as a timed F/D system.

I imagine the water level in the FT sitting just below the overflow point, about where a siphon break/hole is located. Pump in sump kicks in and raises the FT level the few inches to cover the break/hole and cause gravity to take over and draw water from the FT to the GBs. This will continue to overflow, remaining at the same level until the pump shuts off. With the pump now off, the water level in the FT will begin to drop as gravity continues to draw water, until such time that the break/hole is reached and flow is interrupted.

I found this pic, which looks to describe what I mean (we will assume that "fish water in" is actually water from the sump and "return" is water to the GBs)



As you see, the water comes in, filling the tank and starting the siphon. Once that inflow stops, the water level will again drop, until air is drwn into the open pipe. Once water is again pumped in, the siphon will start, pump stops, water drops, siphon breaks.

SO...the whole point of my confusion is there is not CONSTANT HEIGHT IN FISHTANK at all...there has to be some fluctuation. At least in a timed F/D system...

vlt, I think he just misunderstood what you were trying to say.

No doubt it would help him to do some reading.

Ok, first of all, I want to apologise for starting a new thread on a very well worn topic....but believe me, I have smashed the search button on this. And google have suspended my browsing priveleges!!

I assure you, I am not one of those ignorant noobs that just asks questions because he's lazy and can't read. If I honestly cannot get my head around something, I will ask about it, ONLY after I have performed due research. I'm a pretty clever and practical sort and there is not alot that stumps me, but on the odd occasion, there will be an exception to that rule.

One thing I hate about internet forums, is little snots that ask basic questions, because they cannot be arsed even attempting some research. I get this a lot on Aquarium forums and it drives me up the wall.

I do also try to word my questions as clearly as possible, but given the nature of written text, it is inevitable that there with be misunderstandings from the askee, as well as the asker.

Anyhoo, cheers to all. I am probably just over thinking the whole thing. I will just need to nut it out.

In your picture, unless water can magically move up the fishtank to get to the hole in the fishtank, there is no syphon/overflow action once the water empties below the outlet.

Search for Solids Lifting Overflow or SLO.

Yep.... And that's why the chift pist style of system doesn't lend itself well to timers being used.

One final thing, I did ask this elsewhere and got a response from faye, but just to make sure I am clear on this: if I have a 1000L IBC as my tank, F/Ding into two 500L GBs (minus 60%-ish gravel volume), will I notice excessive water level fluctuation? ie, will 20-odd Barra be OK in such a system??

Ok, so what are he drawbacks of a constant flood...? Is there potential for root rot to occur with water constantly in the GB?

Just reading back again. Yes, this has hit the question right on the button. The issue I had, I guess, was in the wording of Constant Height...

I couldn't figure how it would work without the water level in the FT rising and falling, even a small amount and your words "there is no syphon/overflow action once the water empties below the outlet" confirms my thoughts. I do know how siphon breaks work and that was the gist of my previous post...

OK, now onto the next puzzle for me to ponder. Stay tuned

And thanks again.