Overflow Standpipes

I too run two overflows, one to the Refugium and one to the Sump...however the Refugium drains into the sump and I have only 1 return pump.

Using the durso style standpipes, I have not gotten them to "balance" while the air hole is small enough to cause them to run in siphon mode. When one is sucking air and gurgling (flushing toilet) the air hole is too small...if you open it up a bit, the gurgling will stop...

However, if you go as far as I have....well past siphoning....then balancing the flow between the two tanks was easy....but now there is a sucking air sound....

As noted above, I'll be building a muffler for the holes and installing it this weekend...

 

So I have to go a bit bigger with the hole? Keep going until I get it?

 

That will stop the gurgling....and get you into a smooth siphon mode....but one or the other will take the majority flow...if you can get it to the sump, that's likely where you want it...as opposed to a high flow refugium....

Is there any way to raise your Refugium and get it to drain into the sump? If so, that will reduce your risk of flooding because of a pump failure... You can reduce this risk as well by adding a high level float switch to each tank that will turn off all return pumps...