overflow box u tube

[gravismaximus]

going to make a diy overflow box. what size u tube should i buy if i was to have a 1.25" bulkhead connector in the box. i would think it should be the same as the hole in the box no matter what size u tube i buy. a 3/4 u tube use a 3/4 bulkhead 1" to 1" and so on. or should they be different sizes? im going to be using a rio 6 powerhead for a return pump. the deadhead is only about 1 ft

 

[acrylic51]

Not sure if your saying your going to make your own U tube or buy, but if you buy they don't have different diameter sizing....standard size....As far as DIY U tube....good luck on bending the tubing smoothly.....

 

[saxman]

U-tubes are typically 1" ID. You simply double-up on them if you need more flow.
Remember that your outflow is governed by your rate of return to the DT, so unless your pump is too "hot", you never have to worry about the flow from DT to O/F box. However, you CAN have "too much" pump, which can pump the sump dry due the the O/F's inability to keep up. This where factoring head loss and possibly bleeding some of the flow back to the sump becomes useful.
HTH