Backyard Aquaponics
A place to discuss aquaponics

Hi!

I am having some trouble getting a loop siphon to work, and I'm hoping someone here can help.

What size tubing and fittings should I use to create a loop siphon on a half-barrel growbed? My pump is a 330gph/1200lph fountain pump supplying both. I will probably be adding a number of additional half-barrel growbeds in very short order once the basic system is sorted out.

The current attempt (my second) is obviously too small, because the siphon kicks in, but the pump fills faster than it can drain. This is using a 3/4 inch threaded to 1/2 inch barbed fitting, and 2 feet of 1/2 inch tubing.

Many thanks,

Fishfarmer Ellie

Divert some of your pump output from the grow bed (fill it slower).
So what I'm suggesting is you divert some of your pump output straight back into your fish tank, put a valve in place so you can adjust the flow to your growbed and just adjust that to get your loop to work.
This will help you understand what flow rates will work for your loop and then if you want to go bigger you'll have an idea how much flow you'll need.
Hope this helps.

John's got the right answer.

A quick update to close this thread.

For the full output of a Lowes 330GPH(nominal) pump, with a head of ~3.5 feet, a 1/2 barrel growbed can use a 3/4 hose with a 6 inch diameter loop for a reliable autosiphon. A 1/2 inch loop does not flow quickly enough, and will be overrun by the pump. If the pump's output is split, i.e. to feed another growbed, then the 3/4 siphon will not start reliably, and will have to be downsized to 1/2 inch tubing.

Further, the output tube of the autosiphon should be all downhill like this. \ If there is a "hump" in it like ~ , then it will "air-lock", and the siphon will continue to drain water at the same rate it it pumped in. It will also make obscene gurgle-gurgle-poot noises that delight a 6 year old interminably.

-Ellie

Good point on the downhill run EG, some of us have found that out - we just let the end of the siphon drain into an open pipe

You could try one of these...

Or this...Add your own container.

We are trying to scale down the Flout to fit your needs and price.

Most of my loop siphons are using 3/4" or 1" ID tubing though I do have a little tiny bucket using a 1/2" fitting down to 3/8" ID tubing but that is running off a pump that can't even lift water more than 24".

1/2 barrels can be tricky to balance inflow with outflow on an auto siphon sometimes since the rate of change of the depth in the barrel varies depending on the depth of the barrel.

Hey Sparkchaser.... new units looking like a practical size for use...

How about updating the "flout" thread with the pictures and dimensions.... keeps it all in one place for easy reference... especially with future updates ....

Don't want to be a newbie (but I am)... what is a flout?

It is an alternative automatic draining device. Flout stands for Floating Outlet. Essentially it is a box attached to the end of some flexible tubing attached to the drain hole in a tank or bed. The box floats up until it can't go any higher then the water rushes into the box, it sinks and drains the tank or bed as quickly as the tubing size and gravity allow.
Developed for septic systems originally.

Quite ingenious really since it doesn't depend on flow rate to kick it in. About the only restriction about flow rate is that the water coming in must be slower than the rate at which the bed can drain. Otherwise, it doesn't matter how slow the water flows in as there really seems to be no trickle over effect with the flout the way there is with siphons.

Drawback is that the Flout takes up more space.

I made a homemade version for one of my grow beds using some flexible sump pump tubing, a plastic sandwich container, some aquarium silicone, a few plumbing fittings and a hose clamp. I had to add a few rocks into it to get the weight and balance right but it works a treat.