Drilling side hole in single vertical overflow

LeftCoastRN · Feb 21, 2021

I bought and set up an older 100g acrylic tank before I knew much about setting up overflows in reef tanks. The tank has a single vertical overflow in the rear corner with an outlet that goes through the bottom of the tank. I’ve set up a hybrid Durso system (see pic) to help reduce the noise, but it is far from silent...and still too loud for our living space. I would also like to resolve the risk of a major flooding incident if that one output become obstructed.

The tank is in place and I have no reasonable way to move it, so after much deliberation and research, I have a plan. My plan is to drill a hole in the side or the overflow about 10” up from the bottom, place a 1” bulkhead with the threads on the outside of the tank. I will then remove the hybrid Durso and connect a gate valve to the output under the tank. I’ll then use a 90 degree street elbow to the bulkhead inside of the overflow and connect a Durso to it. (See my awful drawing).

Fortunately the side corner that I will be drilling, placing the bulkhead, and having a drain hose go around and into the stand, is on the side of the tank away from entranceway to the room so it won’t be a total eyesore for me.

Is this a reasonable plan? I can drain the overflow and plus the bottom outlet while drilling so I can avoid any plastic dust get into the tank during the drilling. Is there anything important that I am not taking into consideration? Thank you much!

laverda · Feb 22, 2021

That should work. A dorso is not really needed I just use 45 degree pvc on most of my drains. I clean them up by removing the edge on the inside corner so water flows over them smoothly. I prefer this method as I don't need to fool with a gate valve. I don't even have one. They are quite at various flow rates, which is a big plus if you change you return pump flow for whatever reason.

LeftCoastRN · Feb 22, 2021

laverda said:
That should work. A dorso is not really needed I just use 45 degree pvc on most of my drains. I clean them up by removing the edge on the inside corner so water flows over them smoothly. I prefer this method as I don't need to fool with a gate valve. I don't even have one. They are quite at various flow rates, which is a big plus if you change you return pump flow for whatever reason.

Do you use your 45 degree elbow on an overflow with only a single output, or are you using it as a secondary in an overflow with two outputs? Thanks!

laverda · Feb 22, 2021

I use them on main and secondary. My secondary is really an emergency overflow and never gets used for the most part. I think I only has once in the 4+ years my tank has been set up. There is no reason to glue anything in your overflow so you can experiment.

LeftCoastRN · Feb 24, 2021

Thank you! I don’t plan to glue any of the PVC in my overflow. I’m looking to confirm it is a sane plan for me to drill a second hole in my corner vertical overflow. It is part of the tank and I’m handy with drills, but never drilled a tank and my tank is full of water and life.