Backyard Aquaponics
A place to discuss aquaponics

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!!

My understanding of CHIFT/PIST has always involved two pumps, both in a sump, with one timed and one operating constantly.

In my mental image, I see an FT with an SLO (or similar) feeding a sump below. Water is pumped from the sump back to the FT, at a rate that maintains a constant level between each (similar to the relationship between sump and display tank in a reef aquarium). Intermittently, a second pump (also in the sump) kicks in, filling the grow beds for a timed period. Water from the GBs then drains back to the sump, where it continues to cycle to and from the FT.

Upon further reading, it seems I am completely wrong in this...it seems there is only one pump, in the sump, with water overflowing from the FT to the GB's, draining to the sump, where it is pumped to the FT again. To my understanding, this can only work on a constant flood system...is that correct? And if not, how does it work in a flood/drain situation...??

Syphons in the grow beds

Grow bed fills up, syphon kicks in and empties grow bed, syphon breaks and grow bed fills up, syphons kicks in and empties grow bed ............ add infinitum.

Would it not also work for a syphon system where it fills slowly and drains quickly?

Or you could have a timer for F&D. As long as you are filling it quicker than it drains and the switch of the pump and let it drain?

No such thing as a silly question my friend. GB drains to sump tank, pumps from sump tank to FT, SLO in FT feeds GB. Simple.

Whether it be syphon drain or CF, you regulate the flow by either ball valve from FT output or A "T" that comes from pump line back to sump.

Correct; run the pump until all the beds a full and overflowing over the TOP of the standpipe then the pump turns off and all the water drains out of a small hole at the BOTTOM of the standpipe.

CHIFT PIST (Constant Height In Fish Tank Pump In Sump Tank) refers only to how the system is configured but will work with constantly flooded beds, syphoned beds or flood and drain via a timer.

Hmmm, clearly need to think harder!! Lol. I guess sometimes the simplest things are the hardest to grasp...

If there is water draining from the FT to the GBs, there would need to be a period where the FT was not overflowing, otherwise there would be a constant flow, however slow, into the GBs, no? And this would mean the FT was not constant height...

Isn't there meant to be a period where the GB is almost completely devoid of water??

Maybe I'll go look for a .gif somewhere...

Edit: Just read your second post again ff...so there is some variation in FT depth, even though only a few inches whilst he pump is on?

Btw, I'm curious about this because I am still unsure whether to incorporate a sump into my system. I have the Dingo Digger man coming Monday and I want to work out where to dig holes. Also, a sump seems a great place to raise fingerlings away from larger fish in FT...

http://www.aquaponics.net.au/Chops.html

here is an animated version, click the start pump to see.

Its referred to as CHOP on there

No, most plants thrive in a constant flooding environment.
Check the BYAP trials thread

I love my constant flood!

With a no-time/siphon method, the water will constantly flowing to the GB. GB will fill, but when siphon dumps water into sump the inflow is such that it takes a while to fill the GB again and activate the siphon again. This period when the GB is filling is when you get o2 to the roots.

With a timer on the pump. Your FT will not be constantly draining to your GB.

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.

OK, I think that clears that up.

Looking at that animation, it seems the cycle needs to run pretty much constantly, the only proviso being that the siphons can evacuate the GBs faster than they are filled...

But what if I want to run a timed system? ie. Flood GBs, allow to drain, wait, Flood GBs, with the pump coming on every sixty minutes, so there is a period of little to no water flowing into the GBs. Is this a true flood and drain system? Also, going on the animation above, many folks have their systems switch of completely over night, only running during the daylight hours. This is something I am also interested in...but it seems this would not be possible in the animation, otherwise the FT would drain itself dry (unless there was a siphon break drilled into the SLO)...

The SLO doesn't siphon, abd most
People run continuously.

Hey

I run a timed flood and drain CHIFT PIST system without problems...

I have it timed so that I turn the FT volume over at least once an hour.....

I use affnan siphons which have worked perfectly since day one......

jT

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.

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...