Sizing overflow pipe

[FishFlake]

I want to build a pvc overflow but I have a question I need answered first. Thanks for any help with clarifying this for me.

After figuring out the head for my set-up, my pump has a capacity of about 300gph. In the Pipe Sizing sticky by CHOMPERS, the max vertical flow rate for 3/4" pipe=337gph; 1"=600gph; 1 1/2"=1350gph. Also, in another post (I believe CHOMPERS again), it's mentioned that the overflow should have 4x the cross sectional area as the return. My pump return is 3/4" so based on this, I should make my overflow from 1 1/2" pipe. My question is, why? And why shouldn't I use 1" pipe which seems to have plenty of capacity for this flow rate?

 

[FishFlake]

Anyone?

 

[KaiserSousay]

Just me, but I would go with the one inch pipe.
Just build the thing and not fret about it.
PVC is cheap.
Get a couple buckets outside and test the heck out of it.
You might be surprised at the results.
You might end up back at the pipe aisle or not.

 

[Spiritofthesoul]

I think for overflow pipes, Larger is better.

You won't have to fret about whether it can catch up with the output rate and should you decided to upgrade your pump, you won't have to change the pipes as well.

 

[Pharaoh]

I would use 1" as well.

 

[FishFlake]

Thanks for the feedback. I'm heading to H Depot today, but I'll probably wait a few days before testing. It's 27F out there right now.