I think you are probably going to want something food-grade, not something that had motor oil in it.

Perhaps you could line the drum with a heavy-duty plastic bag?

If it were me, and I was growing just for myself (not giving extra produce away to family and friends), I'd just clean it out as thoroughly as possible using something to break down the oil or whatever was in it (I'd probably use Simple Green since it's safe for plants on its own).

The plastic liner is a good idea, definitely do that if you can. Be sure to use something thick enough that it won't stretch or tear on you.

The blue or white plastic food grade drums would work the best. You can find a complete how-to here:

http://www.fastonline.org/content/view/15/29/

They use fish but you could use store supplied nutrients as well. Youtube has some user built stuff online that shows some nice setups.

Here is a link that might be useful: Barrelponics

If you can't get food grade you could probably just get some of the enormous plastic trash bags to line the non-food grade kind.

That's not a bad idea either way, since it makes it easy to clean the tanks. Drain, throw the bag away, put a new one in, you're done!

I don't see any reason you could not use it, but I can see 30-35 reasons for not doing it. One, that's a lot of water to fill and empty. Not to mention the pH up/down to balance the water and the nuits to get your ppm or EC where you want it.

Considering 5-gallon buckets are a buck, two-thirty nine (real cheap) or even free, I would opt for those and use the drums to collect rainwater or turn into compost bins.

Mike

True, but if you're operating a large system a large reservoir is invaluable. Say you're running drain to waste... the bigger the res the less frequently you have to refill. If you're running a recirculating system the big res is a lifesaver because it acts as a massive buffer to changes in pH and ppm.

How many salt-shakers can you dump in a lake before the water tastes saltier? Bigger-res, less fluctuations.

But as you say, that does make for a bigger chore when it comes to draining and filling. If you've just got a few plants a 55 gallon drum is overkill. If you've got a commercial greenhouse it's not going to be remotely large enough.

You've got to pick the right reservoir for the right application, simple as that. Just like everything else (right lights, nutes, etc)

hooked,

I may have misread the OP - I thought he was going to use the drums to grow the plants in, not as a res for water. With your scenario it would make fantastic sense. Thanks!

Mike

I think growing in metal drums is not good. You will probably have your plants becoming ill due to the metal components leeched from the tank itself. As people have said, they should be covered with plastic in order to prevent this effect. Furthermore, I would recommend washing it with a solvent that can truly remove motor oil (such as petroleum ether) otherwise it is just not going to come off. Either way, once cleaner and lined, it seems great to grow citrus trees, haven't you thought about this ?

Here is a link that might be useful: Everything Hydroponics

Good point there, I was just thinking of the big blue plastic drums you often see in use in hydroponics.

If it's a metal drum you will absolutely want to get it lined.