Overflow design on a drilled "new-to-me" used tank

[BigBassB]

Picked up a super nice 210 with pre-existing holes drilled. I plan to retrofit an extra 55 gallon I have for the sump, but wanted to talk through my overflow design to ensure my thought process is accurate. If you have a better way, I'm happy to hear your suggestions as well. I haven't purchased yet, but looking at getting a Sicce Syncra Silent 5.0 return pump (1321 GPH).

Pre-existing bulkheads
1 - 1 1/2"
1 - 1"
2 - 3/4"

I would prefer a bean style, but based on what I'm working with, a Herbie is probably my best option.
The plan is to use the 1.5" drain as an open channel, the 1" as the full siphon, and both 3/4" bulkheads as returns. I put together a quick diagram to help visualize. Any issues or potential improvements on this design? Thanks for the input!

 

[T-J]

Let's first start with your return pump. That pump isn't going to work. With zero head, you'd be lucky to get 1300gph. Get yourself an actual return pump.
I would also use the 1.5" as the main drain, with the 1" being the emergency overflow.

 

[ca1ore]

I assume the sump will be in the stand (so not massive amounts of head pressure). I cannot speak with direct experience to the Sicce 5.0, though at moderate head it should be fine for a 210. Your plan for the plumbing makes sense to me. A 1“ siphon will handle full flow just fine. I thinks it’s always wise to use the largest pipe for the open channel drain. Dual 3/4” is a bit unfortunate as that will put quite a bit of friction drag on the pump … and may be necessitate a larger one. Have you the ability to over-grind a larger hole?

 

[BigBassB]

I assume the sump will be in the stand (so not massive amounts of head pressure). I cannot speak with direct experience to the Sicce 5.0, though at moderate head it should be fine for a 210. Your plan for the plumbing makes sense to me. A 1“ siphon will handle full flow just fine. I thinks it’s always wise to use the largest pipe for the open channel drain. Dual 3/4” is a bit unfortunate as that will put quite a bit of friction drag on the pump … and may be necessitate a larger one. Have you the ability to over-grind a larger hole?

Right on. Unfortunately there isn't much room the way its drilled. Probably not a good idea to try to go bigger there.

 

[BigBassB]

This thought just occurred to me. What if I use both of the 3/4" as full siphons, keep the 1.5" as the open channel, and use the 1" as a return?

I also decided to go with a Jebao DCP-8000 pump instead of the Sicce.

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[rhitee93]

Following along to see the thoughts on this.

I'm in a similar situation designing the overflow for my first sump on a 120 gal setup. The custom tank will have two 1" bulkheads and a single 1.5" bulkhead. The tank designer recommended that a1" would be plenty of flow for the drain with the 120gallon tank, and that the 1.5" should be the emergency.

I bought a Synchra 7.0 based on the 7' head I am expecting.