Backyard Aquaponics
A place to discuss aquaponics

yep, either that or an autosiphon (TC has drawn a loop autosiphon)

If you're using a timer you could always put a valve on the drain side and regulate it with that, or on the drain from the fish tank, not sure how that would affect the suction of the venturi drain

looks like steem beat me to it, here is my post anyway.

There are two choices of how to achieve flood and drain.

1-you can have a fairly powerful pump (one that can fill the grow beds in a shorter period of time) on a timer and when the timer shuts off the grow beds can slowly drain by gravity back to the sump tank. An overflow placed at an appropriate level in the grow bed can ensure that the bed will only fill to the appropriate height even if the pump runs a little longer. The amount of or size of the holes letting water down the drain in the grow bed controls how fast the bed drains but it still needs to drain slow enough so the pump can fill it up.

2-you can run a smaller pump all the time and achieve flood and drain by the use of an auto siphon of some sort (or FLOUT, or some sort of other automatic draining device.) In this method you have the benefit of being able to use a much less powerful pump but you have to balance flow rates if using auto-siphons on the grow beds. With an auto siphon the level rises until it overtops the auto siphon which will then quickly drain the grow bed until it sucks air and stops allowing the grow bed to fill again. There are Bell siphons (sometimes spelled syphon) There are loop siphons and there are FLOUTS. The Siphons can be niggly to get working properly if your flow rates are not quite right for the pipe size you choose or if your really restricted in elevation for the outlet of the siphon. FLOUTS are great in that they are not nearly so picky about flow rates but they take up a lot of space which is a big drawback. Any other automatic draining devices are likely to be kinda like a flush valve like in the barrel ponics manual or they will require some extra know how which I don't have.

as usual, it's better to wait for TCLynx to write something

TCL, you beat me to it! Now I have to cut 75% from my post!

Muj,
Neither involves valves as they are very expensive. The two methods (as TCL so clearly explained) are:

1) flood-drain (pump on timer). A typical cycle is 15 on, 45 off. The drain and overflow are often combined in one vertical tube with an open top (overflow) and holes drilled near the bottom (drain), with a second drilled tube around them to keep out roots and gravel. A concern I've heard is that pump and timer may wear out with the frequent switching.

2) autosiphon: Parts of the growbed (especially where water is flowing in) will always be filled with water and the pool of water tends to spread unless one stirs the gravel a bit to break-up the solids clogging the gravel. Some (like me) sometimes have an issue with the siphon never completely shutting off so the growbed never fills, but can be quite reliable and the ability to flood and drain with no moving parts has a certain elegance.

Is my guess correct? Please see the attached picture.

Is point 'A' should be right at the bottom of Grow Bed?
Is the siphon pipe should be raised at the top level of grow media inside the Grow Bed as shown in point 'B'.

Is there a strict level for keeping the height of point 'B' in relation to the Grow Media?

I'm thinking that the 'on' time of the pump should be the time it takes to start siphoning. But how long should the 'off' time of the pump be?

Hi Muj.... basically right mate..

Point "A" is usually at the bottom of the growbed.... but doesn't strictly need to be...

Any water remaining will be mixed with oxygenated water during the next flood and drain cycle... so there's no problem...

Point "B"... is your siphon "trigger" level... the maximum height to which you want to flood your growbed... usually we suggest that be set to 25mm (1") so that the top of the growbed media doesn't generate an algae growth/slime which would smother the oxygenating roots close to the surface...

Timer based systems are often set to flood... 15 mins.... and drain 45 mins...

Again these are not rigid... and your climate and choice of media may require a more frequent flood/drain cycle...

As far as I know, the siphon system you are picturing has a pump that runs continuously, at least that is how I've always done it. There is no on/off cycle.

On/off is usually used with standpipes, not siphons.

Timed pumps can be used with siphons, they're great for when you're testing your siphon, and don't want to lose heaps of water. Or when you just can't get your siphon right...

Timers on pumps are certainly not necessary with siphons, and not many people use them.
Siphons are great (even with a timed system), because they drain so fast.

To get a siphon system nicely balanced, put a Tee at your pump outlet, with a tap on it, allow this to go back to the sump. That way by opening the tap, you can reduce flow into your GB to get it all balanced.

As Rupe said: Point A is the lower level of your water, and Point B is slightly below your upper level of water. The more difficult your siphon is to start, the higher the water will be.

Loop siphons are great, because they make sense to ppl, and you can see how things work.
However you may find you want to progress to Bell siphons once you understand them, as loop siphons being flexible, move when full of water (this sometimes helps them to start, if the inflow is too low) and they also have a tendency of moving when dogs, cats and birds come to investigate. Bell siphons in my experience are the tanks of the siphon army.

Ahh yes... very true... neglected to point that out...

Is there a general ratio for sump volume versus FT volume using this type of design?

Sump volume needs to be related more to the grow bed volume. I personally think a sump should hold at least 60% of the total volume of all your grow beds. (grow beds when filled with gravel often average to needing about 40% of their total volume to flood them so I add 20% extra to allow for some extra sump volume for pump and float top up valve etc.)

How much grow bed you should have related to your fish tank volume will depend on your intended stocking density. Do you want as much fish as possible for your fish tank? If you want as much fish as possible in your fish tank, then you probably want your total grow bed volume to be twice that of you fish tank or what they would call a 2:1 ratio grow beds:fish tank. In which case a sump tank that is equal to your fish tank would probably do. If you are gonna be a little more moderate in the stocking of your fish, then having grow beds = your fish tank or what they call a 1:1 ratio is probably fine and your sump tank could be as small as 60% of the grow beds.

Since most people want to grow their systems in the future, it is often best to make the sump tank match the fish tank in size even if you don't need it so big to start with, more water only makes the system more stable anyway.

Thanks that was a pretty good explaination. I was planning inially a 1:1 ratio on GB to FT and stock accordingly. I lke this design . I would assume that the Fish Tank needs to be elevated to provide good flow to the Grow beds? I was also wondering how you would prevent the solids coming from the Fish Tank from clogging the distribution lines to the grow beds.

Pump pumps up to tank, tank level rises, overflows (which sucks the crap off the bottom in TCLynx's drawing), that water ends up on the beds, the beds fill up because they're draining slower than the pump is pumping (so there is more water flowing into the growbeds than out of the growbeds) then the pump turns off, the water from the tank stops flowing to the growbeds, and the growbeds slowly drain to the sump (because there is no further inflow of water). So essentially the level of your water in the tank stays the same, but the level in your sump (and in your growbeds) changes. i.e. The water volume from your sump ends up in your growbeds.



Yep, regulate by the number of holes. Check this guy out:



The top of the standpipe is on the right of the picture. Or better yet, just check out this picture:


The little cut out "C" peice around the top allows you to slide it up and down to adjust the top level of the standpipe. The bottom connector piece can be rotated to give you faster or slower draining (because the holes line up better or worse depending on how you have it oriented). Allows you complete control.

The distrobution pipes to the grow beds need to be big enough to allow gravity to drain the water from the fish tank through them about as fast as the pump is adding to the fish tank. I've not had a pipe that was large enough clog. The trick is gravity flow pipes must be bigger than the pipe from the pump since water under pressure will flow faster than water under gravity through the same size pipe. I would advise against doing a grid of pipes with holes to deliver water to the grow beds, those would clog.

thanks for all brothers. this clears a lot of my guessing at things


so what size pipe do most folks run on the SLO?