Pump too strong.....

I agree, probably the T.

There shouldn't be an air bubble in the u-tube once you are able to open up the pump.

 

I dont get how that makes a difference at all. Many people T off of the drain and have a seperate line that is valved off providing a low flow to a refugium area.

One thing to note is, I have not moved the overflow box inside the display. If i increase the return pumps flow, the water level rises in the display and gets higher up the "teeth" on the box. It currently is still running and at this power all the bubbles are being pushed down over the back of the tank/U-tube. However, if I throttle the return pump to even more flow, the water int he display continually rises and the over flow cant keep up.

I think I am going to install my extra Digital Aquatics float switch inside my display so that if the return pump begins overpowering the overflow box, the float switch will trip and shutoff my return pump before it floods the display.

 

The problem the O.P. is having remains and is really quite simple IMO. The reason I asked why he is using such a big pump is because IME you never want your pumps rated output being so close to the maximum output of an overflow. Overflows are inherantly dangerous as it is and doing this is a recipe for disaster. Over time pipes get less efficient. Slime starts to coat them and even calcification sometimes occurs, not to mention if a snail were to happen to make its way into the overflow and partially clog his inlet pipe.(I have seen this happen actually) or somehow a bubble forms in the utube. If your overflow is just barely big enough to handle the pump then this is dangerous IMO.(although normally if the outlet pipe is building up obstructions the return pipe will as well) Now I realise this doesn't really help the O.P. as he has already purchased his pump and overflow. Just want others to be aware that I wouldn't recommend doing this.I always use the rated output of the pump without accounting for Head pressure to match up pumps with overflows giving some wiggle room so to speak.(or even smaller as you can supplement flow with the use of powerheads which IMO is better anyway but be aware too small also has its dangers i.e. bubbles may form in the utube))Also I realise that others may have used t's on the returns but everyones system is slightly different so the problem remains. Fittings constrict flow. The more (and the type) you have the more they will effect the flow.Good luck.8)

 

Honestly I couldn't disagree more. If you do it that way, you raise the risk of breaking the siphon in the u-tube, which is by far the riskiest part of an HOB overflow set up. An 800 gph pump at 0' (which is what you suggest) would probably put out 500-550 gph at 4', which is far too low for a u-tube overflow rated up to 800 gph. Air will accumulate in the siphon, which reduces flow rate and may break the siphon completely. I recommend buying a larger pump, and then using a valve to fine tune the flow rate.

Anyways, we both agree that the T is the problem here. The OP has our suggestion, it's up to him whether to implement it.

 

I will remove the "T" this weekend and just have a vertical drain pipe. I believe the problem is that I have a T and the water just stops and goes seperate directions. I need to figure out a way to include a seperate Refugium run-off line that does not impede the vertical flow. However for now.... I will just use a straight vertical drain pipe (until i move and upgrade tanks.... then I will have a refugium.).

Will update once I fix this bad boy up.

 

Reconfigure the tee on the overflow so the main flow to the sump goes through the straight leg and the refugium or other flow comes out the side outlet. The tee is causing a restriction or head loss since the water slams into the side of the tee and must change direction to continue. You want smooth laminar flow when gravity is concerned.

 

Well I have removed the T added a vertical 45 and it seems to be working much better. I am definately able to dial the pump back less now so it is pushing more water through. I have it slightly set above where the bubbles were occasionaly accumulating int he siphon.

Also, I did as i stated earlier. I have programmed my Reefkeeper Lite float switch to shutup off my return pump if the water level in my sump drops too low. This will shutoff the return before the pump will overflow the display . Its a nice fail safe to have.

I think everything should work okay and its been running fine for a few hours now with the water levels not changing. I am going to go to sleep and I think i can sleep comfortable tonight. "Knock on wood". The added float switch as another failsafe really adds more comfort.

 

Glad to hear you got everything working. I like the float switch safety feature.

 

Think you missed the point of my response. I am just saying when finding a pump for an overflow it is best not to get too close to the max. output of said overflow.Also since different pumps react differently to head pressure this was just an example of where to start.(I should have been more clear about that) Its been my experience unless you constantly want to tinker with a valve (also has its dangers) it is much easier to just pick the correct pump.Done it this way for years with no problems.
Good luck Anthos!