cismot

Salam perkenalan buat semua malay reefers in Sg. Harap leh belajar from otai2 kat sini. from cismot

Drill a hole at the topmost of the U tube, attach an air valve (make sure to seal it - airtight). You can manually suck the air inside the u tube using yr mouth (easier done with a long airtube attached to the valve). Close the valve tightly after doing this. You just have to make sure that the siphon does not break in a power failure. A better way is to attach the air tube directly to a powerhead venturi. The powerhead will suck the air for you, just make sure the valve is always open for the powerhead to suck air out.

Roughly, my U pipe is 2" diameter PVC accomodating a 3000lph return pump (if im not mistaken). Donno exactly the best size for a specific flow. IMO in theory U can use a deeper inner box, as long as the critical depth is maintained during power loss.

I think this is not right. The siphon *should* continue normally after a power loss. U might have a tank which can accomodate all your sump water but this is not what we ultimately want am I right? You might want to take a closer look to your o'flow design. Your outer and inner box should be roughly at the same level. In a power failure, both the U tube ends in the boxes *must be submerged* in the remaining water to maintain siphon. Please note the critical depth between the standpipe opening and U tube opening in the diagram - this is the key to maintain the siphon.

FYI, I'm now using the same overflowbox design. It is okay to use two PVC elbows instead of using U pipes. Optionally for the small siphon-starter tube, u can attach it to the venturi of a powerhead, so u dont have to manually suck the air using your mouth.