Donna,

Water will seek its own level. This means that water in one barrel will equalize with the water in the second barrel(if connected by a pipe of any size) so the water level or water elevation in both barrels are the same. This axiom being said, if a lower barrel's top edge is lower than the barrel it is connected to then that barrel will overflow. When you say smaller barrel, I assume you are saying a barrel with a smaller volume. If that is the case, two barrels of the same size or volume would hold more than barrels of different sizes. I hope that is clear but probably not. JMHO aloha

Maybe he was thinking that the second barrel had to be smaller (shorter) for the water to flow into it? I don't know what he was thinking, but I figured he would know. However, before I ordered a smaller rain barrel, I googled how to piggy back them, and nowhere did I find that the second barrel had to be smaller. He must have some logic behind his thinking. I think the problem is that the bigger barrel is sitting on one level of cinder blocks to raise the barrel high enough to get my watering can to fit under the spigot. And, if what he says is true, and I need a smaller second barrel, I wouldn't know how to fit the can under the spigot (if it must be lower). I would need to put TWO levels cinder blocks under the first (making the first barrel higher), and one cinder block under the second. Wouldn't that need additional work on my drain pipe? Am I explaining it correctly?

I would rather have a larger barrel as we are in a drought right now.

Thanks for your reply.

Donna

Donna,

lehua13 clearly explained the basic theory behind linking multiple rain barrels. But to reiterate, water seeks equal levels in two containers, if linked by a common pipe. Therefore, both barrels should be of equal size and positioned at the same height above the elevated base.

Any change in size or position will result in reduced volume capacity.

Thank you.