CPR Overflow Problems

[Jobiwan]

Howdy, I've got a 40 running with a CPR overflow, I'm having ongoing problems with it. The water level in my tank rises above the intake to the point where I don't get any surface skimming, an oily slick forms on the surface. A couple of weeks ago my tank overflowed, the overflow intake is an inch below the top, the water level had to rise about 1 1/4" above the intake to overflow. The aqualifter seemed to be working fine, but I replaced it anyway. There is no air visible from the side of the overflow, there does not appear to be any stuck in the overflow. I have made sure it is level. After the flood I removed it and cleaned the interior with muriatic acid, no obstrictions such as snails etc were present. When I shut off my pumps the water level drops below the intake as it drains into the sump, when I start the pumps again the overflow works great for a few hours, then the water level gradually rises again. I tried changing from an MD-7 to an MD-3 for the sump return pump, absolutely no difference could I see. Any ideas?

 

[james734]

What to plumbing look like going into the sump. Any sharp bends or anything that might be restricting the flow.

 

[Scooterman]

http://www.reeffrontiers.com/forums/showthread.php?t=19901&highlight=overflow

Krish has lots of experience with these, try looking @ this to see it if can help!

 

[mmkeeper]

Do you have to air tube that extends out of the strainer at the bulkhead? Make sure it is not plugged. Is the strainer clean? Are you using pvc or tubing??? Make sure their is not an air bubble in the line. Is the aqualifter spitting water?

 

[Jobiwan]

I appreciate the replies folks, in answer to your request for more info:No plumbing restrictions, I used 1 1/2" flex PVC, the water falls down the drain tube as fast as it comes in (we're talking about the output of an MD-3). When I disconnected everything I verified there were no obstructions in the drain tube. Screen was clean, although in the last couple of weeks I removed it to see if it would make any difference, no change whatsover , no surprise there though. Aqualifter spews air initially after my drain down thingy, rapidly goes to water only, no variation in water output once it gets going after the air is out.
Thanks again,

Joe

 

[joshinjosh]

What is the ratign on the cpr overflow?

 

[mmkeeper]

Do you have the acrylic tube that goes thru the screen bulk head. Make sure it is clear( that you can blow air thru it).

 

[Krish]

It almost sounds like the pump is slightly too big for the overflow. Do you know which model CPR overflow you have? If there was a major problem with the setup, I would think the water level would rise right away, but the fact that it takes a few hours to get to that point almost sounds like a slightly over rated pump for the overflow which is why you probably don't see any issues till after a few hours running. If it is easy for you to put a "Y" on your sump return and have half of the water re-circulate back into the sump and the rest back into the tank, then I'd give that a shot with less gph of flow flowing back into the tank and see if that solves the problem. If it does, then you know your pump is a bit too strong. Just a thought...

 

[riemannp]

Seems very clear to me that your pump outflow is exceeding the flow capacity of the CPR. As you say, your tank water rises gradually until it achieves enough hydraulic head to push this flow through the CPR.

I have a valve immediately downstream of my return pump (an external pump). Assuming you have the same, why not just throttle it down and experiment. You could "Y" back to sump as noted above or perhaps just keep the flow throttled down.