Pond Boss Forums POND CONSTRUCTION Building a dam Pipe overflow?

My Dad has a drain in his garage made from a 55 gal drum that has used this method (high level outflow pipe with an elbow down into the basin) of drain for 45 years. He put it in this way to try and keep sediment from washing cars from entering his drywell.

It works as you hypothesized - as the water level reaches the bottom of the outflow pipe, it also rises inside the down-turned elbow and begins to exit the basin.

It's not actually an elbow - he used a "T" with a cap on top so he could access the vertical pipe from the top in case it needs cleaning. I would recommend the same approach in your pond overflow in case the vertical pipe gets clogged.

Note that the vertical pipe will always have water in it and will therefore be subjected to freezing (and quite possibly busting) if temperatures get low enough for that.