overflow height?

[jandree22]

my dilemma is I want to make my overflows low enough to be effective moving water, but I want to ensure that under normal operating, that the water level remains above the tank trim... I hate the look of tanks where the water line is visible. I don't care if the water line is visible when the return pump is off.

is there any general rule or common depth below the tank trim that I should go for, not sure how to determine how much depth above the overflow threshold the water line will exist. I guess I should mention I plan to use 2 - 1" drains in a 75, utilizing 90* elbows inside the tank facing down... to implement a durso type design. if any of that is confusing, let me know!

 

[Anonymous]

The depthe above the threshold is related to the size, shape and number of combs the overflow has, as well as the flow rate of the return pump. There is a general rule of thumbs. Most design is about 1/4 inch to 1/2 or so if the pump is sized properly.

If the line is too high, you can run the risk of the water overflow down the side of the tank if there is some clogging or other type of build up on the combs. We tends to make it more safe by lower the water line a bit. There are many ways to help this. Water level monitor, for example, can shut off the return pump in the event of overflowing. Another option is to lower the canopy so that you can't see the water line.

 

[Anonymous]

trial and error.

My teeth are 1 1/2" down from the top, and I think I have 12" of 3/8" teeth. with my chiller in line my tank is down about 3/4" from where it was without. So level also depends on your return rate.

B

 

[jandree22]

Okay, well I’m using 2 - 1” drains and my return pump is an Iwaki 30RLT, so I’m only expecting about 420gph return after basement head loss. Because the drains themselves will handle much more flow than is being returned, I’m guessing I’ll have relatively little water height above the threshold depending how wide I make my slits.

I’m also going to try to rig up mounting the overflow boxes directly to the PVC rather than siliconing it to my tank, which would eliminate the silicone to acrylic concern as well as allow the boxes to be removable, so I can make adjustments if need be.

Thanks guys

 

[jandree22]

Okay, so here's what I'm thinking specifically for DIY overflow boxes… seems too easy like it might be flawed. Rather than cutting 10 pieces of acrylic to make boxes, I was thinking about just getting 2 of those specimen containers (I'd knock off the hanger piece). To attach them to the tank, rather than actually adhering them to the glass, I was thinking of drilling a 1¾”” hole in the back of the specimen container, then integrating them with the bulkhead fitting to hold them in place. So it would go…

Bulkhead nut --> Glass (tank) --> Bulkhead gasket --> Specimen container --> Bulkhead fitting
(Outside tank -> -> -> Inside tank)

The bulkhead gasket would be doing double duty by sealing both the hole in the glass tank and the hole in the specimen container. If I ever wanted to remove the overflow boxes for cleaning or even initial trial and error of setup, I could just manually drain the tank below the glass holes, and disassemble the bulkhead fitting and remove them.

What problems, if any, am I not seeing with this setup?

 

[kgross]

You will need one more gasket inside of the box (specimen container in you post) under the flange. Otherwise water can leak under the flange and then flow down the threads out the tank.

This actually works very well though and is how I install overflows in tanks that have water in them. Lower the water level as low as you can, drill hole, install overflow fill back up. You don't have to wait until the overflow is glued in to put water in. This is also how glass-holes.com does there overflows.


Kim

 

[jandree22]

You will need one more gasket inside of the box (specimen container in you post) under the flange. Otherwise water can leak under the flange and then flow down the threads out the tank.

oooooh, yeah... excellent point, thanks!! I knew I was missing some minor detail.