Questions for those who have a HOB U-tube type overflow.

[trilinearmipmap]

1. How do you prime these overflows?

2. Does the siphon ever fail?

3. Do you need a minimum amount of flow rate to keep the siphon from failing?

4. How is their noise level?

5. Is there any problems with siphon resuming after a power outage? I am thinking of running mine only at night to a refugium if the noise is too much.

[andsoitgoes]

1) Fill the water enough and it'll start automatically

2) Yes, it can - I've not experienced the issue, but the small system I wsa running isn't up anymore. The new one, which I purchased from a board member, has never been an issue.

3) I'll tell you next week, I'm going to be pushing about 50 - 70 gph up from the sump - will that be enough to keep things flowing? Who knows.

4) Again, not sure - but depending on the design, it would make sense that it wouldn't be MUCH louder than a standard overflow. As long as the water level remains the same, it should be okay.

5) If you have a venturi into the u-tube, that should go a long way to keep things going as soon as the power starts again. I think you might be tempting fate to do the off/on thing, though. It could just be extra risk that you really don't need to take... But I understand, mine is in the bedroom and it's going to be, well, interesting.

[4ptbuck]

1. How do you prime these overflows?
you stick airline tubing up into the top of the U-tube and suck the air out.

2. Does the siphon ever fail?
Yup, if the waterlevel falls below the u-tube, it will fail just like any other siphon. Mines has a small skimmer/overflow box inside the tank. When the water level falls in the tank, ie a water change the inside the tank box stays filled with water. The one problem I had once, was that there are 2 holes in the box whereas 2 suction cups plugs into to hold the box to the glass. One of the suction cups pulled out and the water flowed out as I did a water change, hence dropping the level in the box and breaking the siphon.

3. Do you need a minimum amount of flow rate to keep the siphon from failing?
nope, it stops during a waterchange, whereas there is no flow.

4. How is their noise level?
Better than a inside the tank overflow, as the water typically falls equivalent to the depth of the tank. With tweaking, mine only falls less than an inch.

5. Is there any problems with siphon resuming after a power outage? I am thinking of running mine only at night to a refugium if the noise is too much.
I'd suggesting running it 7/24. Seal the suction cup holes, and mount the inside box in a different manner. I use liverock to prop it up and wedge it against the back.

[hawk]

I had a lifereef overflow. The tubes were in a overflow box inside the tank so the water level never dropped below the tubes. So even if the tank water level dropped during water changes the level inside the box never dropped enough to break the siphon. The siphon would stop (but not break) when the return pump stopped (power outages, etc.) but always started when the flow started again. The only time I ever had to restart the tubes was when I took them out for cleaning. As for noise it took some occasional tweaking but for the most part was quiet.