for my 300g with a 1gph drip system. i used 1/2" pvc. the only thing i need to do is lower the output about a 1/2 inch, the water level stayed a little to high, install the check valve and intake screen. it is going to drain into a tee under the sink with 1/2" hose. it never lost siphon and stopped flow at the bottom of the output.





i think the main thing about a diy overflow is understanding the concept. im not looking for certain max flow #'s like for a sump application so tubing size wasnt really a factor.