Can anyone advise on setting up a prefilter box?

[parliament28]

I'm installing an Amiracle Pre-Filter Overflow box onto my 20 long and have some questions about setting up my sump/refugium. I reasearched a fair amount, but this plumbing stuff/ RC Calculator is all above my ability to comprehend, so any help would be greatly appreciated.

The overflow is fitted with a 1 inch bulkhead that will run to a 10 gallon below. It is 36 inches down from the bottom bulkhead in the overflow box to the bottom of the 10 gallon, although I will have to install a 90 degree elbow to lign up the PVC directly below the 20 gallon and into the ten. So I plan to use 1 inch piping to flow into the refugium and 3/4 inch piping to run it back up to the tank. Couple of questions:

1. Should I install valves to adjust flow rate coming from the overflow box to the sump, as well as a valve from the pump returning water?

2. What is an appropriate sized pump to return the water? Will an overflow box only return water as fast as the pump pushes it back up, or if the pump is underpowered will the u tube lose siphon?

3. Can I use flex tubing rather than PVC for the up or down flow (this might be easier to work with, correct?)

4. Can I run a single return from the pump without any problems? It's going to be a tight fit as is with a 24 inch aquafuge and 6 inch overflow box on 30 inches, so I plan to run the return over the top aquafuge and into the tank (it'll look weird, but for the extra volume from the sump I'm determined to do it.

Thanks in advance

[ErikS]

1. Should I install valves to adjust flow rate coming from the overflow box to the sump, as well as a valve from the pump returning water?
Not really necessary, but it can help you adjust the backpressure on the drain line. This will help you quiet it down. The one on the return line is only needed when the pump can outpace the overflow. With a well built & tuned "Stockman" pipe the need for adjusting the backpressure is lessened to a great degree.
2. What is an appropriate sized pump to return the water? Will an overflow box only return water as fast as the pump pushes it back up, or if the pump is underpowered will the u tube lose siphon?
The size of the pump is determined by your desired flow & the capacity of the overflow (about 6 - 700gph). You can always use a valve to throttle back a pump. Yes, it will only drain water as fast as the pump puts it into the tank. Yes, if the pump is wildly under powered you could have bubbles build up & loose a siphon but I've run mine very slow (100gph) & it still clears bubbles - this isn't generally a factor as we tend to use as large a pump as the overflow will handle - lol.
3. Can I use flex tubing rather than PVC for the up or down flow (this might be easier to work with, correct?)
You mean flex PVC or vinyl tubing? The flex PVC is great, you can eliminate or ease some of the bends. Vinyl tubing is fine, just remember this will require the use of hose barbs which will reduce flow in the line.