New tank design graphic ... Tell me what you think...

[Myka]

Originally Posted by Megalodon

That is correct. The backup overflow is higher than the other two. The backup drain line also doesn't have a gate valve and it's completely unrestricted.

In your drawing it looks like all your bulkheads are the same height. How are you going to get your backup overflow higher than the primary overflows without having to keep your entire tank water level much lower than the rim of the tank? You need to have quite a height difference between the backup drain and primary drain(s).