Sounds about right! I think we call them rain barrels too, in some parts of the country. It's a bit daft, really, even if you had a set of the larger ones, they still wouldn't have sufficient capacity to hold the amount of rain we have in winter ... and in the summer, in a dry spell, they only hold enough for a week or two. In my house they only take the water from the porch roof and the roof over the lean-to. Rainwater from the main roof goes down a drain set in the middle of the roof and running through the inside of the back of the house (in 1973, when the house was built, it was considered an innovation)! I suppose any little helps, though.