What can you do when your overflow, doesn't?

[LCDRDATA]

I come home from work to find my sump almost empty and my main circulation pump mainly sucking air. I initially think I forgot to top it off (no ATO), but after adding the first gallon and going back for the second, I realize it's already sucking air again because nothing is coming back down - there's no flow through the overflow. I've checked the tubing, reamed out and flushed the siphon port, cleaned the aspirator pump (Rio 800 RVT), and done about everything else I can think of. Even with lots of bubbles coming through the aspirator (demonstrating suction does exist), the "out" side of the overflow box doesn't start flowing. I'm thinking that perhaps the interior inverted "U" is plugged up, but can't think of a way to clean it without breaking something (flex brushes, etc just don't seem to go in). Any thoughts on a solutions (or even alternative causes)?

[surf&turf]

Is this a CPR overflow?

[LCDRDATA]

Yes. It's the dual 3/4(?) inch model rated at ~ 750 gph.

[surf&turf]

Will the pump pull water/air thru the siphon hole?

[LCDRDATA]

Yes, it does. But at this point that doesn't seem to make any difference.

[surf&turf]

So the overflow is not filling up with water at all?

[surf&turf]

Can you shine a flashlight in the side and see if its clogged? I clean the siphon port on mine every couple days. Try running a pipe cleaner or a bread tie down it and make sure nothing is clogging it.

[LCDRDATA]

Not really. There may be some minor fluctuation in the water level, but it won't fill sufficiently to start spilling over.

[LCDRDATA]

I've done that, and when that didn't work, I've "backflushed" the siphon port with both air and water - no change.

[surf&turf]

Where is the pump located that pulls your siphon? I use aqua-lifter pumps and they sit on top of the overflow.

[LCDRDATA]

It's down in the sump.

[surf&turf]

Any way to move it up to the display and see if that helps. The pump may be getting weak and won't pull the siphon that far.

[surf&turf]

You can also start it manually, but you will need something to cap the port or the hose that you use. I wouldn't do this for an extended period but will get flow back to your sump.

[LCDRDATA]

I may try that in the morning; at this point my tank's gone to bed and I'm about to. Thanks for the suggestion; I'll post the result one way or the other.

[LCDRDATA]

I've tried priming it that way, too - no dice, although I can't rule out that I'm missing something.

[surf&turf]

It really does sound like something is blocking the overflow part. Mine has tube worms and such, but nothing that would clog the whole thing.

[Steve175]

Buy one of these:

 

http://www.glass-holes.com/700-gph-Overflow-Box-Complete-Kit-gh700kit.htm

 

and never need to wet vac your floor or aspirate tank water again.

[zygote2k]

The Aqualifters need to sit on top of the overflow box for best results. I had 2 of those overflows on a 265 and after 2 Aqualifters dying, the customer decided to go with a Glass Holes 1500gph kit. No more gravity siphons.

[Origami]

In this case, I'd probably put a short length of air tubing onto the box and use my mouth to draw out all of the air in the tube part of the box as a test. Capping the tube off with your finger, you can see if the siphon action starts and sustains. If it does, the problem is not in the box, but in the vacuum used to draw air out of it. There may be blockage in the air tube leading down to the sump, blockage in the venturi in the pump, or not enough vacuum/flow to draw air out that accumulates in the channel and blocks water flow. Years ago, when I had a CPR overflow, I used an aqualifter set just above the overflow to draw the air bubbles out.

[surf&turf]

Any updates?

[firecrackerbob]

I feel your pain! came home to a wet floor last night- I cannot wait to change back to a drilled tank.... best of luck though!

[basser9]

I RAN ONE FOR YEARS I DRILLED IT OUT AND PUT A LARGER NIPPLE IN IT.

You can also put another hole in there with another nipple added just tee it together

and you should never have another problem.

[treesprite]

The Aqualifters need to sit on top of the overflow box for best results. I had 2 of those overflows on a 265 and after 2 Aqualifters dying, the customer decided to go with a Glass Holes 1500gph kit. No more gravity siphons.

I also had 2 running at the same time and had a couple Aqualifters slowly become less and less efficient. I ended up using powerheads instead of Aqualifters, but then they put the air bubbles into my tank. There was one time that the nipple on the CPR OF was clogged and I used a needle to unclog it. At any rate, I will not go back to an undrilled tank if I can at all help it, at least not as long as I want to use a sump or fuge.

[Integral9]

In this case, I'd probably put a short length of air tubing onto the box and use my mouth to draw out all of the air in the tube

 

This is exactly how I started the siphon on my over flow tubes when I used them. The trick is to put the airline on the back side of the tube as the air bubble gets trapped back there when the water starts to flow. If you don't pull enough air out, the force of the water won't be enough to push out the remaining air. Also, the u-tube has low pressure, so if you don't put your finger over the air line before you pull it out, it will suck air back into the tube and stop the siphon.

 

One problem I had with my CPR over flow, that caused me to convert to using PVC pipe was the clear plastic allowed algae to grow inside (yes I know foil will stop it), but in all the cleaning I did to keep it clear, I eventually cracked the tube and that resulted in a loss of siphon.

[LCDRDATA]

Sorry about going dark - work was crazy this last week. I just found a place in the DT to put the Rio I use to aspirate the overflow and it's running fine now - not the most attractive, but at the moment I'll go for working. I'll go back over the thread ( I see it's grown considerably), but thought I should at least post an update.