Durso Overflow & Return question

[Creggers]

Hello all!

I am in the process of plumbing my Marineland 75 gallon reef ready aquarium. Unfortunately it only has two holes drilled, so the Durso style overflow is the only choice for me without running an external return (which I do not intend on doing).

I'm running into two problems currently - the plumbing that came with the system and one I believe that I've created on my own.

Problem one: my drain line is creating a massive amount of bubbles / backwash type sound when it's draining. I believe this is because I have my drain plumbing going too far into my sump and it's creating back pressure... Can anyone confirm before I cut my drain? I also have it going straight down from the display to the sump, no 90* or gate valve to slowflow. I have a gate valve on order in the event that I need to splice that in, but I want to be sure before doing so.

Problem two: The return plumbing has a hole in the corner of the 90*, I assume this is to break siphon in the event of a power outage and prevent water draining back into the sump.. the only problem is an amazing amount of water comes shooting out of this hole, basically filling the overflow and reducing the amount of flow I get in my display tank (not to mention making an annoying amount of noise and undoubtedly creating a bunch of salt creep.

Hoping the R2R community has experienced some of this. I did a quick search and didn't come across anything, so I apologize if this has been posted before.

Attaching a video in a moment from my phone

 

[Ron Reefman]

Do you have an air vent in the top of your durso? That should help with the backing up of water. The end of the drain into the sump can/should be underwater and how deep it is makes little difference.

Bad placement for an anti siphon hole. Most times they are out in the tank and not in the overflow. Maybe that is the elbow that should be the top of your durso and the hole would be for the air vent tube? Otherwise, I'd suggest getting a new elbow and doing a new anti siphon hole in a new spot. Or you could add a small John Guest elbow (like the small hoses used on an RO/DI system. Local hardware stores sell them. You can get one with one end threaded and thread it into the existing hole you have now (you may have to enlarge it).

BTW, I couldn't bring up your video?

 

[Billdogg]

Ron pretty much has it. The only things I would add are that a "T" fitting on the drain line placed so the leg of the T is just above the sump level will allow most of the air to escape before it enters the sump water. The drain line itself should be no more than an inch or so below water level as well.

The only other thing you have to be careful with is the flow through the drain. DO NOT EVER put a valve of any sort on a DURSO drain. You will eventually cause the tank to overflow. In addition, the MAXIMUM flow through a "reef ready" durso (assuming 1" plumbing - pretty much the standard) is 350gph and even then it will be a bit noisy. Realistically, aim for less than 300gph. That is plenty through any standard sump for a 75 btw. The flow in the tank is much easier to control when it is all in-tank via power heads/gyres/wavemakers/etc.

The place where a gate valve is useful is on the return line to the tank. You can easily adjust the flow into the tank until the drain is working well, and it will not harm the return pump in any way to be restricted in this manner.

HTH!

FWIW - every tank I've had since I started in the mid 80's has used DURSO drains. I have yet to have one fail on me.