Backyard Aquaponics
A place to discuss aquaponics

The drainage holes at the bottom of the standpipe are usually 6mm... can be 1 or 2...

And yes, they continue to drain even during the pumping (timed) period....

The pump volume is greater than the volume that the small holes can drain.. so the "flood" rises... with any excess just returning down the standpipe...

Once the pump cycle has finished... the "flood" slow drains down the media.... through the small weep holes... at the standpipe base...

If the system was a constant flow, how big would the sump have to be in comparison with the FT and GBs? I looked in the IBC of AP PDF but it just said it would be smaller than in a flood and drain system, didn't give any specifics. Advice appreciated.

For CF, if the FT is lower than the growbeds then you don't need a sump tank. If the FT is higher than the growbeds then the sump must hold enough to cover the pump (usually you want more to prevent frequent top ups) plus hold anything that would drain into the sump if there was a power outage. This would include what drains from pipes, growbeds, etc ...
Because most of the time you don't have a hole in the standpipe the water will remain in the growbeds. It's also possible to design the pipe layout so that the water stays in the pipes.

In actual practice, you would want some excess capacity (either in the sump of fish tank depending on how you set yours up), to provide for less frequent top ups and rainfall overflows (unless you just put an overflow pipe in for rainfall overflows).

Cheers

Yea your got the jist. Usually 2 small holes at the base of the standpipe (Nat has got a good photo of it), holes about 6mm which when the pump is switched off it allows the bed to slowly drain. Water still drains from these holes when the pump is back on but the incoming volume of water is greater than what is draining so it allows it to refill. A general guide is fill for 15 min and drain for 45 min but its not straight cut and most other variations will work just fine.

p.s. That handshake formula cracked me up EB hahahaha.

Like this...

Thanks Roz, knew there was a pic around somewhere.

Thanks for the advice, the only part I don't understand is that the sump must hold enough to cover the pump. If someone could explain this in greater detail it would be much appreciated.

All I'm trying to say is your submersible pump has to remain submerged to operate properly or it will burn out. The fact it has to be submerged forces you to have a sump with at least enough water to keep it running. This is sort of the starting point.

This is an extra - One way to do a battery backup system with CF;

This might confuse you but I'm going to give you an example where you might want to provide greater sump capacity in a CF system. What I'm shooting for is a battery backup in case the power to the main pump goes out. Basically this consists of a battery with charge controller connected to a regular outlet, a 12 V pump and a float switch. By flipping a standpipe in one or two growbeds so the hole is on the bottom you create a situation where that growbed/s will drain to the sump when a power outage hits (this is why you need the extra sump capacity). When this happens the water level in the sump rises higher than normal and the float switch activates the 12V pump thats connected to the battery. Keeping the system going until the power comes back on.

Thanks scotty, makes sense. I'll try and include a back up pump with a float switch and drill holes in the bottom of the standpipes, will definately help in the case of a power outage.

Hi Angus,

This is just one way to do the backup. Figure out how you want to run your system and go from there. I just wanted you to be thinking ahead, so you don't wind up wishing you had a larger sump if you want to incorporate something like this.

Cheers