Backyard Aquaponics
A place to discuss aquaponics

I have upgraded my system with new growbed, a 1000L IBC and a sump.
The growbeds are fed by gravity from the IBC. The bed uses a bell syphon to the sump.

The issue I am having is getting the flow rate in the sump correct.

I am adjusting the flow rate into the bed and the flow rate from the pump to try and get it even, but I have had the sump overflow, and also run dry.
When it overflows, its holding multiple flood and drain cycles.
When it goes dry its pumping out too fast.

I saw one person use an overflow pipe from the top of the tank into the sump.
I was also thinking about changing the pump to a automatic sump pump.

Is there a best option for this, or am I overlooking something?

I think I may have identified the issue. I think the outlet on the IBC is too low.
It has about 20cm of water above the outlet. This means that the outflow won't match the pump flow.
I will try raising it up to the top of the water level that way it will only drain at the rate of the pump inflow rather than the weight of the water on top.

Okay, so you've increased your growbed volume quite a lot? You need a bigger sump. It needs to be big enough to hold the full water volume of your growbeds (a good rule of thumb for working this out is to calculate the total volume of your growbeds, times 0.4), plus enough water to submerge your pump, and ideally plus a decent amount of wiggle room so that you don't have to top it up every day to keep it just right.

...Or, you can change how your system operates. With constant flow siphoned flood and drain (which is what you've got), every so often your growbeds will synchronise; they'll all be full at the same time (draining your sump to the absolute minimum) or all empty at the same time (filling and potentially overflowing it). One option is to switch to constant flood - just take the bells out of your siphons. You can stick a bell back in one bed at a time to flush them if you're concerned about stagnant zones if they aren't set up ideally for constant flood. You could also try indexed flood and drain (a timer or similar Sneaky Mechanical Trick switches the flow to your growbeds on and off in sequence, and a little hole in the bottom of each standpipe lets the beds that aren't currently being filled drain slowly) which is harder to set up but pretty darn cool and also takes most of the stress off your sump tank.

I'm trying to imagine that and I'm not working out how it doesn't immediately just dump that 20cm of water! Pictures?

I have taps



I also realise that the way I have done it means that if the power goes out, it will dump about 100-200L of water.
I think I should fix regardless of if thats the issue with the sump.

...Oooooh. So you have a 'throttled' gravity flow out of your FT. Yeah, I strongly suggest you switch to a plain SLO that maintains your desired FT water level regardless of whether or not the power is on.

There's a member on here who raised his FT water level by adjusting the SLO piping inside, in a way that would work perfectly for you. I'll see if I can find it and if not I'll draw a diagram. In the meantime, what's the piping inside the FT set up like?

Edited to add: Ha! Found it! viewtopic.php?f=1&t=27639&p=541143#p541143

+1 on the SLO - maintain a constant height in the FT at all times AND collect solids from the bottom of your tank. This will eliminate your problem if the sump is large enough, and it sounds like it is.





I removed my SLO from the inside of the FT so you can see it. The horizontal pipe on the bottom has slits to let the water through. It rises up the vertical pipe and out at the T. You can see the water level from the algae. The outlet pipe is shown in the other photo.

The T is critical as it prevents the water from siphoning out of the tank. With your system you could use a 90 elbow after the T to go back down to your existing outlet, but I recommend the larger pipe diameter, at least 1-1/2" but preferably 2".

The other benefit of the T is an overflow should the SLO become clogged at the bottom or your FT is otherwise over-full (rain?).

Slits in horizontal pipe along the bottom:

your outlet is not too low, it is too small.

although i would have put it higher, the fact is you are stuck with it where it is now, unless you want to buy a new IBC.

add the SLO and extensions people have suggested to get the water level to the right height, but do it in a bigger sized pipe.

OK I have some answers. I made the mistake of using 1" outlet as well so that restricts the outflow from the fish tank. You can fix that by putting a bypass valve in your sump between the pump and FT so any excess water will be diverted directly in the sump. The low hole in your IBC: you can add the SLO but run it above the tank outlet and make a U at the level you want your water. Insert a tee fitting in the U and leave one leg pointed upward and open. This will keep the SLO from creating a siphon and you water level will stay higher. An overflow line wouldn't hurt in case your return line gets plugged. Happens more than you think. Just had a fish stuck in mine yesterday. Always build with "what ifs" in mind.

Or you could just cap off the outlet and install the slo like the pair I did.

I use the flood and drain method with a timer which pumps and fills all GB's in the 15 min period then drains out a 5 mm hole 50 mm up from the bottom of the tank drawing in the air above over the next hour.
The hole size and height needs to be tuned to the pump capacity, the volume and speed of discharge. At 5 mm my first system doesn't quite drain all the way down to the hole before the pump starts again.

Pete.

I will cap the existing outlet and start again.

These are the sizes I am currently using

Sump Pump -> Tank 15mm
Tank -> Bed 15 mm
Bed -> Sump 20mm

I matched the outlet sizes based on the pump outlet.
Which ones should be enlarged?

The bigger to pipe diameter the less resistance also removing sharp bends helps the volume flow.

Sump Pump -> Tank 15mm. Ok if it provides enough volume otherwise go up a size.

Tank -> Bed 15 mm. Really it begins with the slo which many recommend no less than 50 mm then reducing to suit dispersion fittings minimum 20 mm at GB, beware of small taps having the ability to clog.

Bed -> Sump 20mm. Depends on the drain method I use a 40 mm.

Pete.

Plug your inch outlet
Set up a big one as high up as you can with a SLO as suggested
Run water to your growbed / growbeds (you will end up with more haha)
Run excess flow back to sump

Problem you have going on description and pic is you will need LOTS more flow through your fish tank to keep it clean the fish waste will pile up .

If your only supplying / running one 1 @ 25mm siphon you have around 220 / 240 liters an hour through your tank

If you have a full size IBC you need 4 times this flow at a minimum

Generally agreed that we should "Turnover" our fish tank water volume every hour at a minimum

How you set up your beds is personal preference. I use bell siphons and once they're set up they just keep working. The problem I see with timed systems is pumps and lines changed volume over time and that could cause issues. With the bell siphon if the volume increases it just drains more often and if it decreases it will just become constant flood. This will indicate you have a problem and you can correct the problem without creating other issues. I've never used the timed method so I'm not discounting it by any means. I would do 25mm feed lines in any event with 50mm drains.