grow box outa pvc?

Sounds good, I've done the same thing before to make drying racks. Inexpensive, lightweight, and very sturdy (considering the weight). If you plan to hang your lamp from the wood ceiling, your frame is going to have to be pretty sturdy. You may need more than four PVC tubes attaching the floor to the ceiling, and I would add four extra horizontal pieces halfway up the verticle support beams. Alternatively, you could build a 6' tall wood buttress to support your HPS lamp and just place it inside.

If you want it to be airtight, it's going to be a little tricky, however it sounds like you're planning on using a regular box fan or something in the top, as opposed to an inline fan. This would certainly exchange a lot of air from inside the flowering room with the surrounding area, making it pointless to attempt to make the seal around your chamber airtight. Are you planning on using odor control within the room you place the chamber in? Are you making a closed loop system using A/C? Or is odor control simply not a problem where you're growing?

EDIT - Also, a 400w HPS in a 4'x3' floor space seems a little small (33.33w/sq. ft.). You may want to consider a 600w lamp (50w/sq. ft.) for an area that size. A 400w will grow some alright nugs, but if you want some fatty dense buds go for the 600.

 

PVC is great, I use it for all kinds of little construction projects (didn't for my grow box, though). Should work fine. Corners can be tough, I've never found a 3-way connector that has 90 degrees in the same plane and then a separate 90 degrees off in a different plane, as you would need for the corner of a box. You can work around that by using a 90 degree elbow to turn the corner and then a very short pipe segment to a T junction to connect the vertical support.

I suggest reversing that fan, drawing air out from the top instead of pushing it in from there.

I also think you could have more of an issue than you think with odor. building a 4x3 footprint, I'm guessing you will put half a dozen plants in there or more. That could really stink up an apartment.

BTW, if it's your own apartment, can you convert a closet instead of building anything in the first place?

 

I have to agree with toasty on all of those points. Pushing air from the top to the bottom will force the air over your HPS lamp before going over your plants, which will really heat the canopy up. Hot air rises, and it's best to exhaust your air from the highest point in your flowering chamber. I would have the fan on the ceiling exhausting air out, and have the vinyl covering around the chamber open about 2 inches before the bottom of the structure as your passive intake. This will draw the coolest air possible in to your grow room (the air closest to the floor) and exhaust the hottest air possible out. Also, how large is the room that this chamber will be in? If you threw all of this in to a walk in closet or something, the heat buildup would be too extreme. If it were in a bedroom, however, and your apartment has A/C, that would be fine.

I don't believe the glass tube for your light will be necessary. The fan on top will not be pushing the air through any ducting, so there will be very little back pressure and very high exchange rates. If you do use the glass tube and an inline fan, you will not need the ceiling fan. Since you will be using a light mover, I think you're right in changing your specs to 6'x'2 as opposed to 3'x4'. Have the light move a total of four feet, and try and keep it two feet above the canopy. These dimensions will also make training your plants to the screen easier, and you could get away with only having to open and access one wall.

Odor will also be an issue. The problem with apartments is that someone else owns the property, and has every right to enter the apartment for maintenance inspections. They are required to inform you in advance if they need entry to the unit (where I live, at least), however getting your system out of there would be a real hassle, and with ScrOG, I doubt you would be able to save your plants. Also, any friends/family that visit you will undoubtedly catch on, and when growing, it's best to keep things on a need-to-know basis (you should be the only person who needs to know, unless you have a spouse or serious live-in partner). Placing a negative ion generator in the room probably won't be enough, and I don't recommend ozone generation, as O3 will damage your plants.

And yes, I forgot to mention toasty's point on making corners with PVC boxes. The way he described it is how I did it, however because you're using a wood board for a ceiling, I think you could do it a little differently. Use the T-fittings as he described, but ditch the 90* elbows. On the bottom, the ends of the T-fittings will rest on the ground, providing the small opening as your passive intake. For the ceiling, make your wood platform the exact size of your box's floor, and drill holes on all four corners with a diameter equal to the diameter of your T-fittings. Then just place the wood ceiling on top with the fittings going through the holes.

Any ideas on what you will be using as far as your hydro system goes?

 

<table border="0" margin="8" padding="0"><tr><td valign="top"></td><td valign="top">Out of curiousity, after posting the last message I did a quick Google search and found this. Never seen one of these at my hardware store, and it is only available in one size (3/4") on this site, so I think they're pretty rare. I'm sure you could order them off the web, but that just seems kind of silly to me.</td></tr></table>Image links to source web page.

 

When using ScrOG, I like a plant spacing of 1'. In your 6'x2' room, that means two rows of 6 plants, or 12 plants total. Both the Eurogrower and WaterFarm only support 8 plants. With the WaterFarm, you could add on four more buckets, but the total cost would be pretty high (about $450). If you wanted, you could build the exact same system fairly easily for about $100-$150, tops. Keep in mind though, with this system you won't be able to fit your reservoir inside the flowering chamber, so make sure you have room right outside the box for the res.

I personnaly don't like squirrel cage blowers (Daytons). They're incredibly loud, and perform very poorly under backpressure (caused by the ducting attached to the blower). I would get a 6" inline fan instead. They're much quieter, last longer, and blow more air (a LOT more). I would then ditch the box fan in the ceiling, and connect the inline to an aircooled hood or tube for your HPS. Then connect the exaust of the fan to a carbon filter to eliminate odor. You can build your own carbon filter for next to nothing, or buy a store-bought one.

 

Cool Agro, that's the corner piece I've never been able to find either. Nice!

 

Sorry, I've been out of town (sorta) for a while and couldn't respond. A 10 gallon for two plants sounds adequate, but remember bigger reservoirs provide greater stability for your plants. I like to super-size my reservoirs when using any recirculating hydro system, so I would probably use 15-20 or more gallons. However, that's just me, and I'm fairly certain you will be satisfied by the results of a 10 gallon reservoir as well.

Only two plants? Have you changed your ideas on the design/size of your system?