Flood duration time question

is there a specific amount of time the flood cycle should last ?
found a lot of info on amount of floods per day , but not so much on duration of flood .
My system is sort of a flood and drain /top feed hybrid .
I have 169 4.5“ pot with clay pebbles
Each pot has individual open 1/4” line and pretty much floods from the top . Need some help figuring out how long to flood for at each feeding .
thank you

Typically in flood and drain you only flood long enough to achieve full depth then start the drain cycle.

With the top feed there probably isn't any reason to achieve full depth, or any depth for that matter. I'd just make it a recirculating top feed drip with the tray as the collection device. Or even better just flood and drain.

Renfro said:

With the top feed there probably isn't any reason to achieve full depth, or any depth for that matter. I'd just make it a recirculating top feed drip with the tray as the collection device. Or even better just flood and drain.

Click to expand...

I was going to just do flood and drain , but the guy at the shop I was buying from told me that I would run in to problems later in flower because feeding from the bottom causes salts to build at the top because it never gets flushed from above . Is this incorrect ?

tileman630 said:

I was going to just do flood and drain , but the guy at the shop I was buying from told me that I would run in to problems later in flower because feeding from the bottom causes salts to build at the top because it never gets flushed from above . Is this incorrect ?

Click to expand...

Well with flood and drain the fluid also drains out of the bottom. I have done a lot of flood and drain in my years and I never noted any particular issues with salt buildups running flood and drain.

Salt buildups occur when bottom feeding pot of say peat based mix that is allowed to soak up nutrients from a saucer but nothing ever drains back out, so it's just a constant input. In this case a periodic flush from the top is required to rinse out the salts. If growing in organic soil then we aren't using salts and bottom 'feed' is only h2o so this is good and flushing would only rise out the limited supply of organic nutrients.

Renfro said:

Well with flood and drain the fluid also drains out of the bottom. I have done a lot of flood and drain in my years and I never noted any particular issues with salt buildups running flood and drain.

Salt buildups occur when bottom feeding pot of say peat based mix that is allowed to soak up nutrients from a saucer but nothing ever drains back out, so it's just a constant input. In this case a periodic flush from the top is required to rinse out the salts. If growing in organic soil then we aren't using salts and bottom 'feed' is only h2o so this is good and flushing would only rise out the limited supply of organic nutrients.

Click to expand...

my concern with drippers was that with the tables completly fully it would be hard to tell if everything is opperating correctly , didnt want to have to worry about drippers clogging .
my plan was to water fast and let them dry out . when i run the system it has a ton of flow and fills the tray anyway even with a 2" drain ,but stays at a consistant level about an inch from the top of the tray. tray is a low tide so its only 3.5" deep.
In your opinion will the system i have work or is it somethng you think i should change ?

Damn, it must have a lot of flow, pretty hard to out run a 2 inch drain. You have any pictures?

tileman630 said:

my concern with drippers was that with the tables completly fully it would be hard to tell if everything is opperating correctly , didnt want to have to worry about drippers clogging .
my plan was to water fast and let them dry out . when i run the system it has a ton of flow and fills the tray anyway even with a 2" drain ,but stays at a consistant level about an inch from the top of the tray. tray is a low tide so its only 3.5" deep.
In your opinion will the system i have work or is it somethng you think i should change ?

Click to expand...

If you're going top feed/drip, it should be a light trickle - no way it should out flow your drain man. That said, I would stick with a basic f&d like @Renfro said. In my last tent, I converted my basic f&d setup to top feed (just for fun) dtw and it was not worth the hardware/hassle. Basic f&d; no glitz or glam but it works like a damn charm. Regarding the guy at the grow shop, as a general rule, never trust the guy in the grow shop lol. Seriously though, he's partially correct depending on the medium you choose. As an example, if you're using what most people use in f&d which is expanded clay pebbles/hydroton/leca, you will be fine however I have heard that coco, pete, and rockwool are prone to buildup without top feeding/flushing (though I have no direct experience). When I ran f&d, i ran 3gal fabric pots with 75% hydroton 25% grodan grow-cubes (chosen so that I could have a slight buffer in the event of some failure in feeding); it ran issue free that way until it was converted.