Backyard Aquaponics
A place to discuss aquaponics

I am not sure if this has been covered somewhere before or not but I just came across the issue and figured out a solution that I figured I would share with the site.

So... Normally when you have a hydro flood and drain table that is operated on a timer you will have two holes drilled in the bed. One is the pump inlet and the other has a short stand pipe in it to set the water level and act as the drain. When the timer turns off, the water back flows through the pump and back into the sump until the bed is drained.

What do you do if you are using a centrifugal pump that is not self priming with a check valve or if you don't want the water to flow back through your pumps impeller?

I installed a check valve bypass by using a reducing T on the inlet to the trough. There is enough friction loss created to keep the water flow going into the bed until the pump shuts off. Then the water will drain back through the inlet but turn through the bypass instead and go down the normal drain line. Works flawlessly.

(inlet has the gate valve)

Sorry for my ignorance, what do you use the flood and drain table for? Is it a seedling table? Or similar to a flood and drain media bed?

I'd love some more information on it!

Hey Colum, I use them for seedling and micro green tables but you could use it with a media bed as well. I know a lot of members run media beds so thought it might be usefull.

I've been tempted to build a dedicated seedling table, and another for sprouts for chickens.

Do you keep the flood and drain table on constant use, or turn it on and off during the day?

Keep the info coming!

It depends on your temps, evaporation rates and type of media but right now I'm flooding 1x every 5 hours for 5 min.

Sorry, I'm going to bug you with more questions, I've been contemplating this for a while. I've been trying to start them straight in the DWC, and they are hit and miss with when they pop up. I tried an indoor temp/humidity controlled area, but without spending more than I wanted on lighting, they weren't growing well. Lettuce come up without a fault, but stuff like basil is very stubborn.

Do you seed soak the seed or anything? And how big do you let them get before transplanting? And what media do you set the seeds in?

Sorry, I know I'm a pain.

I'd love more pictures of your flood table. Looks like it's made out of pond liner?

Going back to the piping bypass system Ryan do you:-

a, have a dedicated pump for the tables?
b, when pumping into the table have a portion of the water go down the return line via the reducing Tee?

Smathew- 4x4 legs, 2x6 frame, ABS plastic bottom, liner. Similar to my old backyard floating beds but with legs.

Slowboat-yes , a dedicated pump. Yes, a small flow backflows through the bypass. Sort of like a Venturi, this could be overcome with a larger outlet and smaller inlet but it's not enough to bother me in this application. Here ate a couple short vids showing this:
http://vid229.photobucket.com/albums/ee245/Stoneymahony/Mobile%20Uploads/IMG_4381_zpsae95273f.mp4
http://vid229.photobucket.com/albums/ee245/Stoneymahony/Mobile%20Uploads/IMG_4380_zps194f087a.mp4

Such a pain!!!

I think you will definitely have better luck using a flood and drain method to start seeds rather than soaking them in the flood bed. A lot of seeds don't like to be soaking wet when they sprout. I use rockwool (and some coco) and only pre soak peas and beans. I transplant when they start to get full root protrusion out of the starter cube. With a flood and drain table you can go longer b/c the roots will Airprune. Another low-tech way is to use a Rockwoll starter cube slab of 98 and place it a 10" x 20" starter tray without holes. Get the slab soaking wet before planting the seeds and then don't water it again for 2 to 3 days until it starts to dry out. And water until it is soaked again and repeat the same process. You will get to the point where you can just tip up the trays and feel the weight and tell if you need to water or not. I did this for several years and had very good success.