To my knowledge it there is a power outage it will drain to a point and stop, like any overflow, and in terms of getting clogged, I think it could happen, but could be easily cleaned with a brush. if I wasnt going drilled this is the one I would use personally

That elbow at the end with the open end up (not shown in my pic) will kick in if the overflow slots get plugged. And yes, with a power outage it can only drain down to the level of your lowest slots. And it can't drain below that T at the back either.

Like I said, I tested it extensively, and could not think of a scenario where it could fail. Just make sure everything outside of the water is properly glued and airtight.

Of course the absolute best is a drilled tank, but if for some reason you can't drill it, or don't want to, this definitely works.

I don't understand this design. Do you have an exemple in pics?

So I guess the only disaster scenario is if air gets inside and it lose syphon? then it wont work and the water coming from the sump is going to overflow the tank. I guess putting the pump high enough so not as much water can be sucked if it overflow is a good practice :)

Looks great anyway. on a 15 gallons nano I don't want to drill or put anything in the tank beside the pump and that overflow pipe. It really look good with only these.

Oh cool! thanks a lot. That will make it nearly impossible to build up air inside. So far I have tested it and there is still a good syphon after being not in use for 24 hours so I guess the air is not getting inside but I want to be safe!

I already have such pipe at the intake of my return pump so all I need to do is drill a small hole and glue a air tube like in your pic.

OK, I took another pic, this time with the elbow in place of the cap at the end of the slotted overflow tube. You can cut the top of the elbow to get the 2nd level emergency height to whatever you want.

It doesn't matter where you place your return pump. It is the overflow design itself that regulates the water level in your tank. In my case I actually was using a canister filter, and just stuck the input hose into my sump, with the airline plumbed into the intake side. This way I could switch the input to either my tank and use it as a QT, or to the sump and use the tank as a refugium. Many ways to do it. As long as the siphon airline is connected to the intake side of the return pump, you can't go wrong.
http://www.canreef.com/photopost/dat...edium/0031.JPG

[quote=daniella3d;668817]What I like about those pipe overflow is that they take very little space and are not so ugly as the boxed ones that are sold. I have a black tunzee one that I don't even use as I find it too ugly and if you want the water level to be high in the tank this thing need to be so high that it is really ugly. The pipe overflow is very nice and can be hidden in a beautiful home made box and the water level adjusted very presicely.
QUOTE]

Have you looked at notching the top of the glass and adding an external overflow to your tank? No ugly boxes or pipe in the tank what so ever and no space used up in the tank. I don't know if the tank is empty or not so this may or may not be an option for you.

I like this design with the slotted tube & elbow as emergency. Was thinking it could even be modified by having two emergency drains. The elbow at the end of the slotted tube looks good, but what if you were to replace the 90 that the slotted tube is plumbed to with a Tee? That way the open end of the Tee would be your emergency. Might be better in case the slotted tube gets plugged internally. In that scenario, your elbow at the end of the slotted tube wouldn't help. Anyhow, you could do both & have double protection.

Yes, Mike, a T at the beginning of the slotted tube is even better and I would just put the cap back on the end. You really need only one emergency, as it is big enough to handle any flow that could go through the slots. I would just have a little screen cap or something over it to prevent fish from jumping in.

The beauty, too, of this design, is that the tank side plumbing does not need to be glued, and you can keep making adjustments to fit the tank until you are satisfied with the design.

When I was actually using this overflow as a refugium, I only had the slots (no emergency elbow) and macro algae, chaeto, caulerpa, etc, would collect there, but it never came close to plugging. The slots allow a lot of flow, and as the water rises, more slot area becomes available on the pipe. But I did keep an eye on it, and was planning to add that elbow on the end if necessary.

While we're on the subject of modifying designs, for adjusting overflow tube height you could add a 'slip union' to the tubing. Here's a picture of my skimmer with one of these unions incorporated into the return line. It's just above the ball valve used to regulate water column height in the skimmer. Using one of these unions will enable adjustment in the neighbourhood of 3 inches on the overflow. Sufficient for most applications.

https://tsl4pa.blu.livefilestore.com...15d.jpg?psid=1

Yeah, if you wanted to get real fancy, a slip union would help. But like I said, the inside tank plumbing isn't glued, so some room for adjustment up and down anyway. I still have a good portion of a 20' PVC pipe left over, so no big deal cutting new pieces.

I see you like DIY stuff, too. Good job...

I am setting up another 140g tank downstairs, and trying to figure out all plumbing in my sump room. My current 100g DT is upstairs. I will share the same sump initially, but then will set up another sump into this already tight room. Never ends...