Why...

[Wing Commander]

do dams and dry docks always have what appears to be a controlled leak?

[GTIR]

Or overflow.

[john2443]

I assume you mean why is there always a bit of water leaking in to them?

Because it's pretty well impossible to completely stop every leak so it easier to leave the small leaks and pump/drain that amount out than it is to seal every leak.

Applies to locks as well.

[Condi]

Stops the sea running out of water, by having a leak it ensures there is always some being pumped back in.

[NDA]

Wing Commander said:

do dams and dry docks always have what appears to be a controlled leak?

It's not just dams and dry docks, it applies to some people too.

[cal72]

I leak. (to much beer) I overflow (to much beer). Enough said.

[4988cc]

This is all vagina euphemisms isn't it?

[Wing Commander]

Hehe!

The reason I ask is that I am currently doing some contract work in a dry dock and it is got a constant freaking leak which just annoys the OCD side of me.

Then I remembered that dams almost always have a hole in the middle piddling a trickle of water out all the time. And someone above mentioned canal gate thingies too.

Understand that it is near impossible to stop all the leaks, but for some reason I had it in my head that it was done on purpose.

Praise be to the power of PH!

[King Herald]

Wing Commander said:

do dams and dry docks always have what appears to be a controlled leak?

It's not a controlled leak. It is just a leak that is small enough to not need fixing.

Not sure about dams, but I've been in plenty of dry docks. Usually floating ones though.