Overflow drains rates 1",1.5" PVC ?

Reign1 · Sep 17, 2023

Just getting close to install. I have a 30" cube tank I got a screaming deal on.
Has a traditional overflow with 1.5" and 1" hole. Addiionally has 2) 1/2" drilled returns on bottom of tank ( I really don't like this as can be a huge issue if power out even with good check valve.
The real question ... I am going to use a RO Varios 4 strictly for return and also have a RD x that will likely be used for UV and accessories (rtn to DT).
What is max drain rate on 1" PVC full drain setup? I was considering using 1.5" emergency but with both pumps even turned down I am thinking it will be over 1100-1200 gph.

blaxsun · Sep 17, 2023

Are the drilled returns in the overflow?

Reign1 · Sep 17, 2023

Nah they are in bottom of tank .. I will likely make them at least 1/2 to 3/4 up inside of tank in case of power outtage or run a reverse check valve.

zhenya · Oct 6, 2023

not sure of exact flow, but I have seen as low as 800gal/hr up to 1500gal/hr stated on this site. I’m pushing about 2500gal/hr now and have:
1) 1” full siphon with 4’ drop and 5’ lateral
1) 1” full siphon same set up throttled back because otherwise the pump can’t keep up.
1) supplemental overflow. Just there in case of overflow and capable of going into full siphon. It is a 4’ drop with 2 45 degree offsets to come off the wall 6”.
2) 1” overflow that are valved off for...

So, pending you do not have 500 degrees worth of bends then (1) 1” overflow and supplement drain will work. Each fitting reduces siphon velocity severity, so always minimize bends and go for (2) 45 degree fittings over a 90.

Make sure to put a valve on all lines for the known unknowns. Especially at that low water volume, the 1” full siphon may outpace your pump.

Most def run those bottom overflows as high as possible.

Good luck!

Vivid Creative Aquatics · Oct 6, 2023

I took a cube tank with center overflow and cut out the overflow box. I then use the exiting holes on the bottom glass (original drain and returns) for a closed loop setup.

Then I drilled new holes on the back glass for return and ghost overflow

you can see the process and the result in our build thread

Cube Build - 134-Gallon Cube Build - Random Flow Generator® Powered Mixed Reef - Lots of Pics!

The VCA 134-Gallon Cube - Random Flow Generator Powered Mixed Reef! The first of two new offices tanks are officially under way, and I can’t wait to share it here on Reef-2-Reef Our goal with this tank is to build a mixed reef tank with a unique flow solution that utilizes just Random Flow...

www.reef2reef.com

Might be able to do something similar with yours

Reign1 · Oct 15, 2023

Vivid Creative Aquatics said:
I took a cube tank with center overflow and cut out the overflow box. I then use the exiting holes on the bottom glass (original drain and returns) for a closed loop setup.

Then I drilled new holes on the back glass for return and ghost overflow

you can see the process and the result in our build thread

Cube Build - 134-Gallon Cube Build - Random Flow Generator® Powered Mixed Reef - Lots of Pics!

The VCA 134-Gallon Cube - Random Flow Generator Powered Mixed Reef! The first of two new offices tanks are officially under way, and I can’t wait to share it here on Reef-2-Reef Our goal with this tank is to build a mixed reef tank with a unique flow solution that utilizes just Random Flow...

www.reef2reef.com

Might be able to do something similar with yours

I was considering doing that. I got the tank from a friend and is has never seen water in it and is oldschool corner overflow. I am more considering keeping it way it is. While I have you here the return will be the 2) 1/2" returns will run a RO Varios 4 been thinking of going with 2 of your 3/4" VCA RFG instead of the 1/2 looks like the smaller ones wont take the approx 400-500 gph and 3/4" would be better suited to this?

Vivid Creative Aquatics · Oct 15, 2023

Reign1 said:
I was considering doing that. I got the tank from a friend and is has never seen water in it and is oldschool corner overflow. I am more considering keeping it way it is. While I have you here the return will be the 2) 1/2" returns will run a RO Varios 4 been thinking of going with 2 of your 3/4" VCA RFG instead of the 1/2 looks like the smaller ones wont take the approx 400-500 gph and 3/4" would be better suited to this?

Given the size of the pump (max rating about 1050 GPH) , i would do either dual 1/2in or a single 3/4in Random Flow Generator on your tank.

Our Suggested Optimal Flow (SOF) ratings are based off flow rates at the outlet - after any headpresure loss created by the plumbing. At the SOF flow rate, you'll get a good randomization for about a 10-12% throughput loss (head pressure created by the RFG).

For best results, you should aim for the SOF flow rate or more. If you can exceed the SOF rating, you get a much bigger, more pronounced effect, but at the expense of addition head pressure.

My estimate is by the time the flow travels through the plumbing, your max output of the return, at the outlet(s) will be closer to 700 to 800 GPH

The 1/2in RFGs is about 300-400GPH - two would around 700GPH

The 3/4in RFG is about 400 to 550 GPH, and two would be closer to 800-900 GPH

So - single 3/4in RFG that is significantly over driven, would actually outperform dual 1/2in that are at right at the SOF rating. the single 3/4in RFG at around 700 GPH would create wavemaker-like flow.

Sorry for the long explanation but, its one of those things that, if you get it right the first time, you're going to love it.

we have some flow demos you can view of the RFG at various flow rates. these videos are like 5+ years old, but they still hold true