Hey
@Eclectic Elle , happy Monday
Flood and drain explained
It's very simple system and to be honest soon as my space changes I will be going fully over to flood and drain. Its a no brainier when it comes to watering and man you wanna see those girls go for it in beast mode on a flood and drain table.
The basic idea is that you flood the tray to the hight of the over flow, the over flow then funnels it back into the tank, aerating the water at the same time so no need of air stones and air pumps. Also as the water drains away at the end of the flood, air is then pulled/sucked down into the medium. This is what gives flood and drain its hydro power.
You flood 2, 3 maybe 4 times through lights on. Really It's up to you to build your flood time system but its recommended a minium of 2 floods, 3 being the common number.
The amount of time you flood is really the time it takes for the water to reach the over flow and cause an equilibrium with the pump as it pours back into the tank. I use a digital timer and flood for 7 min, the recommendation is to flood for no longer than 15min.
When it comes to nutrients you want to be using a lot less than a normal straight hand water feed... I like to keep to an EC level of 1.1 - 1.2 as it does like to rise in the tank in hot weather and also you will get those girl's that like to just drink the water and leave the nute's behind. I'm often just topping the rez up with plain RO water to bring the EC back down. One way to spot if your over doing it with the nutes is if you see a slight salt build up on top of the medium you know to cut back a little... EC/ppm meter is kinda needed.
Ph... so far I haven't seen many huge Ph swings with my set up, stay's pretty stable that I only check once maybe twice a week or as I'm topping up.
Here, I drew you a picture
So what do ya need?
Tank... For the tank size you want to be 4 x the amount you want to flood the tray with... for my set up my tray takes 10-15ltrs to flood so I use a 50ltr tank. Its important to have the larger tank, you will be surprised when those girl are thirsty how quickly it go's down. Also if you want to leave the grow for a week you will be wanting 4 to 5 x the flood amount. That's the super cool thing about flood and drain is that you can set it and walk away if you need for as long as the tank lasts.
Important...Tank has to be black or light proof or your cleaning slime up every one to two weeks. I learnt the hard way on that one.
Tray... as long as it's high enough to accommodate the flood anything will do. What to look out for is a tray with a trap or drain away thingies so when the water fully drains away you pots are not sat in a couple of millimeters of water (some thing I have had to deal with, have look at my design)
This is about as technical as it gets on the plumbing. I recommend the over flow to be a larger pipe fitting. Mine are 13mm for the pump and 21mm for the over flow. You will want a couple of spacers to make the over flow to your desired hight... I think Growell do it as a set.
For the pump a downward sucking pump is recommended. It doesn't need to be over powered, I use the lowest rated one.
For the winter and depending on where your tank is positioned you will want to get a 50w fish tank heater
My set up...
That's a 50ltr ReallyUsefull box for the tank (£14 on Amazon), I cut one end of the lid so I can access the front of the tank for easy rez change and re fills.
I fashioned my over flow spacer to fit the pot size (1ltr). I didn't want to flood that high (some pots started to float, funny day that) so I trimmed the spacer down. Again its about your system the flood hight.
There extra little hole you see is there to drain away that last little bit of remaining water. It doesn't quite get all of it but its a minimal amount left after a flood. You can now see why a trap or run off ridges are needed for the tray.
This is how I have got my pipes into the tank, you can now see why I have cut the front of the lid off the box... Yep i did drill through the tent but if your set up is big enough get the tank under the table in the tent.
Hope that helps Elle, think I've explained my self... if you want to see how a master does it I couldn't recommend enough and to watch over and over is Vader Vision of Ocean Grown fame... just on Vimeo at the moment but keep an eye on his YouTube account -
https://vimeo.com/user84087486 its where i have learnt all about flood and drain.