Back-up/ Emergency Drain

[teebone110]

So my tank plumbing is kinda old school, I think I made the Durso drain when they were the best option at the time. I was wanting to add an emergency/ back-up drain inside my overflow just incase my durso gets blocked.
I know it will eventually happen... but I will keep my fingers crossed for now

Any ideas?

I know that I could probably just make an external drain with 2 90's that can run inside my overflow and down to my sump, but I am unsure how to keep the siphon?

Here is a pic of what my drain looks like..




-fixed picture ~blob