diy pvc pipe overflow

My PVC pipe overflow. This isn't the actual thing, just a cad model to show the idea.

This works great. The blue colored pipe goes in the tank. The long horizontal pipe 2 inch dia and is about 40 inches long The vertical pipe is 1.5 dia and about 16 inches.
I tested the flow rate and it's over 400gph. If you want I could try to get a pic of the tank.

 

That's an interesting alternative to other pvc designs. Have you calculated the open surface area along your opening (the slit cut in the PVC)? At first glance you should be able to do more than 400GPH with 1-1/2" PVC pipe. I'm doing almost 1000 GPH with my 1-1/2" setup but it's loud with the waterfall effect. Starting to drive me mad :laughing0

How noisy is the whole yours?

 

I had a bigger slit but was afraid something like a snail would go down. My return pump does about 350 gph so I made the slit small.

As for the noise - it's not bad. Most of the noise goes out of the slit. I keep the glass cover over the back part of the tank and that helps.

 

Do you have a vent tee or siphon break on the outside of the overflow?

 

yes. and at the top of the vent is a cap with a 1/4 hole drilled in it. The cap reduced the noise greatly.
Also, the cad drawing shows an elbow inside the tank where the horizontal pipe with the slit is. I changed that to a tee. The top of the tee is out of the water and again I have a cap with a small hole. This eliminated the air being sucked in thru the slot.

I wish I would have found this site before I made this. I see a lot of designs like this. It took me forever before I came up this this.