I use a Cistern Valve for Flush Control. There are many arguments for and against how we control our Flood and Drain, but I saw one on the internet and had to figure out how to make it work. This idea is not my own. The bloke who did it first was also battling with siphons and posted his version. It sounded too simple. I half understood, but had a little faith and went to buy the fittings. Thankfully God was willing to show me how to make it work. My first attempt was Heath Robison to say the least, but the second was finer tuned and allows one to control a lot of the flood and drain cycle.

Looking into your conventional Toilet Cistern you'll have a similar valve. Operating the lever pulls the valve stem up and it starts to flush. Then when all the water is out the system it seals again and fills up. Obviously you can't flush your aquaponic system all day long so we need a mechanism to flush the system. I place my valve in a header tank which is coupled to my grow beds through a balancing pipe. When the valve activates the water drains from the header tank to the fish tank and the water from the grow beds drains into the header tank to the fish tank. To activate the valve I use a pipe extending from the side of the header tank which fills the 2L bottle. The pipe also guides the bottle up and down through the operation. Inside the header tank the pipe can be adjusted to control flood height. The wooden see saw is my linkage from the bottle to the valve.

When the header tank fills up sufficiently it overflows into the pipe feeding the 2L bottle. The bottle has a 3mm hole and starts to drain immediately. However the bottle does fill up faster and so gets heavier. When it is heavy enough it pulls down on the lever and opens the valve. The system then flushes/drains which ever you prefer to use. The bottle will continue to drain through the little hole till the weights above the valve are heavier than the 2L bottle and it will close again. Then the grow beds start to fill up.

By adding weights above the valve you can control the length of the flush/drain. More weights means the 2L bottle fills more and then takes longer to drain out the 3mm hole. So by watching the level you can either ensure a complete drain or choose a minimum level to drain to by adding and removing weights.

Size of pump is no longer such an important factor, as long as you can get water into the grow beds faster than it drains through the hole, then it will eventually flush.

Here's and overall view of the new system.

Just before flushing. The see saw lever is level. Kind of.



During flushing the bottle has filled and flushed the system by pulling down on the lever and opening the flush valve.



A look inside the header tank with the water level high enough to drain out the red elbow to the 2L bottle outside.



A few second later this happens as all the water drains out, more water comes from the balancing pipe into the header tank. The drain is aggressive so I believe it will pull a lot of air into the grow beds.



The water is draining out the 2L bottle through a small 3mm hole. Increasing this hole increases the length of time the water maintains maximum level. Put a small filter in the bottle cap like those green scrubbing pads. Bugs love water and can block those holes. A weekly checkup is to remove the cap and clean anything you don't want in it out.



The old and the new. The old one worked so well, I won't try auto siphons again. I've learned a few tricks to make them work nicely. The linkage to the valve has slack to allow the valve to align on its seat. Very Important. Keep bugs out the 2L bottle. More important.



This system does require maintenance, but my family can't stay away form the aquaponic system so I'm always looking and tinkering. Every afternoon at 16h45 I sit for coffee with the wife and my four boys. We feed fish and talk about the day. It is absolutely peaceful in our garden and everyday, I know I'm blessed.