There are a few

You mean like this?  Bachmann Plasticville O scale water tower.

http://www.internettrains.com/merchant2/merchant.mvc?Screen=PROD&Product_Code=BAC-45978&Category_Code=

I believe that Lionel also made (makes?) a plastic water tank - though whether it can be purchased cheaply is another matter.  If you're looking for a wooden tank, you might consider scratch building one - they're fairly simple designs.  Another option might be to re-purpose a tank meant for S or HO scales into a smaller branch line On30 tank.

Another option might be to

That's not a bad idea. I'd bet I could do something easily with a HO tank and scratchbuild hardware for O scale...

D.I.Y.

I usually made my own. I used a suitable sized can and wrapped it with scribed cardboard. Scribed wood siding would also work. Balsa wood support posts and NBW castings for the base. Only thing I bought was the spout casting. I,m guessing something like this could be done for under 20 bucks nowdays. Instead of the can PVC pipe is another option. .....Mike

I know where some plans for an N scale one are....

It rivals the craftsman kits. I suppose you could scale it up. The framework for the round portion is made with a couple of wood disc separated by a dowel. It's wrapped in scribed siding. The roof is just a series of triangles cut from paper. The design concept for these tanks is about the same, no matter what the scale.

Michael

Does anyone know if anyone

Does anyone know if anyone makes just the hardware for a water tank in O scale? Some of you make good points, heck, I'd probably spend less time making my own from scratch than I would modifying a kit. I'd probably be looking to make a open-top tank anyway.

Parts

Really the only thing you really need to buy would be the spout. I don't do O scale, but I'm guessing that part of a water column would work. Rest is just chain ,couple pulleys, some NBW's and something for the bands.......Mike

Grandt Line makes O scale Spouts as seen..........

...................here on my scratch built tank.

Peter

Okay, I tried looking at HO

Okay, I tried looking at HO scale and S scale, nothing I found would work in On30...

Man, you'd think someone would make O scale NG water tank that doesn't require you spending as much time as building a full-sized one...

45 Bucks from Banta Model Works!

Peter

"nobody apparently makes a simple smaller water tank"

The wooden tanks were just boards with metal bands holding them together.  If you can find a suitable cardboard cylinder you could just glue wood on it and wrap bands around it. The base would be wooden posts and cross braces, or maybe an enclosed base with wooden board siding.Looks like grandt line has the spouts and maybe even some metal banding hardware? Probably worth checking them out. Do you have a specific style of tank you want to model? .DaveBranum

Have you looked at paper/card

Have you looked at paper/card models. Clever Models  http://clevermodels.squarespace.com/  kits  P/N S52 ENCLOSED HEX WOODEN WATER TANK and P/N S48 THE WATER TANK at GORRE  in O, S and HO scales.

They are inexpensive and deigned to be made into highly detailed models.  If they are too big, they can be reduced in size in size  by printing at a smaller scale (for instance print at 90% instead 100%)  They are in PDF format but can also be opened in many photo editing programs in which they can be modified.

45 Bucks from Banta Model

45 Bucks from Banta Model Works!

I've set a page several years

I've set a page several years ago with plans and a short "how-to" a scratch build water tower you can scale up, but , again, I just read "I just can't devote that much time" .... anyway, I've enjoy "sometime" to spend time to makeup my models

http://xoomer.virgilio.it/enzo_fortuna/Structures_WaterTower.htm

...

Enzo,

Nice write up on making a water tank. Saved your site in my favorites. Might need a couple of these down the line (pun intended) on the Otter Creek Falls Coal & Lumber Co. R.R.

Thanks for the link.

Bernd