Size and number of grow bags for mainlining GDP in 2x4 tent

Hi all, I’m getting ready to start my next grow, am germinating five GrandDaddy Purple seeds at the moment. I’ve been scrogging the past several grows, but this time I wanted to try mainlining. I already have more weed than I can smoke in my remaining lifetime, so experimenting is fun and I can take my time. I just want to be finished by early June because I have travel plans after that.

So now for the main question: With a 2x4 60"-high tent, how many, and what size, grow bags should I use for mainlining? One 10-gallon, two 5-gallons? two 7-gallons?

I have a 10-gallon empty grow bag sitting in there now just for measurement, and from the top of where the soil will be, to the HLG 240w light is only 32", so I am hoping I can keep the colas low enough to not be burned.

Thanks in advance for your time and advice!

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With that many in a 2 x 4 I would recommend 1-2 gallon vessels max Growmie :love_you_gesture:

6 in 1 gallon fab bags in a 2 x 4 x 72

After a defoliation

Before defoliation


I would recommend 2 to 4 bags, at 3 to 5 gallons each. 4 five gallons will end up with a three day watering/feed cycle in soil, and will give a good amount of room around the bags for air movement. This is two square foot per plant, and this is a good size for most techniques. I must admit not sure what mainline is?


It’s in my post pics above. I prefer Nebulas Manifold over Nug Buckets mainline. One less topping. This technique works great for growing more than the space allows for a typical top and training. Keeps the width narrower :love_you_gesture:


Got it, thanks.

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Thanks all. I should have specified in my original post that I am only sprouting all five seeds for safety. The maximum number of plants I would put in the tent is two. I’ll give the other three to my neighbors. I might even grow just one plant.

So with that in mind, should I do one larger container or two smaller ones? And along those lines, would it be of any benefit to use a 10-gallon bag, but squeeze it lengthwise so it’s longer than it is wide? One plant, mainlined, in a 10-gal bag?

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You will probably need to use some type of elevated stand to let air to the bottom of the bag, and prevent the bag from standing in the run off. You may want to consider what you will use for this also. You can get bags in all sizes and shapes including square. Here is what I typically use under a 3 or 5 gallon bag.

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Yeah in all my previous grows I have used small rubber spacers under the bags, but they never really keep the whole thing elevated. Once I decide on the size bag, I will look for one of those that you have pictured here.

Have seen some rectangular shaped crates cut down in height. Or something like a dish washer rack may get you a rectangular shape.

I have one GDP in a 5 gal bag, in my 2x3 tent. Working on a mainline manifold as well, looking scraggly right now

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@ezwicky I use these myself

Looks like a good product for containing run off, while giving an elevation. But in my case the small tent is on a short elevated stand, and sits over a floor drain. So I put a drain tube through the bottom of the tent. This is so easy the run off goes to tube, and then to the floor drain. In the 5x5 there is no drain close by. So I run AutoPots in this tent, and there is no need for a drain. I leaned very early on that a drain in the tent is a very good thing. This is the main reason that I have not just built a grow room in the basement. I don’t want to bust up 30 year old concrete to install a floor drain. I don’t think I would be happy with a full blown grow room without a floor drain.

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@Ickey ,Wow sounds like you got that figured out!!! Those trays wouldn’t do you any good without the hose bib on them lol. I’ll agree with you 100% if I ever got rid of my tents and did a grow room I think you would be stupid not to have a floor drain because it solves a bunch of different problems without them rearing their ugly heads.

That looks so much better than mine. I broke one of the two main stems on one of my plants because the stem was too shart and I tried too hard to bend it. The other plant has four stems now, just waiting for them to get grown enough to do my last topping.

Thanks. I got something similar, not those exact ones. Now I can’t remember where. But functionally the same.

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