An idiots question about overflows

[kdx7214]

I've got a 75 gallon tank. I want to put an overflow. I plan to drill the tank. If I buy one of the overflow boxes with teeth:

1. How do I adhere the acrylic to the glass with some assurance it won't break loose?
2. If I have the box on the inside, do I need another box on the outside with a herbie overflow, or do I just run the Herbie pipes through the tank?
3. Can I just run PVC through the drilled holes (with bulkheads ofc) and just have them vertical at the appropriate water level?
4. What kind of flow rate do I need, and consequently how many and what size holes should I think about drilling?

I've gone round and round looking at information on this and it seems for every opinion there are at least three who see it differently

Thanks!
Mike

 

[WVNed]

Here is a complete overflow. It happens to be the one I use on my 75 gallon tank. It is rated for 800gph.

The box inside the tank is held by the bulkhead. There is no glue.
It comes with
1x 1.5" Transfer Bulkhead

2x 1" Drain Bulkheads

1x Red PVC Standpipe

1x Drilling Template

1x 60mm Holesaw

In the kit
There were several brands of overflows. I am not sure what is available now.

You do not need any fancy piping inside the rear box. You only need a standpipe in one of the 2 drains. The other drain is just a bulkhead with a valve on that drain. SO forget about the herbie and durso and all that.


Here is what I use on my 240. It is glued on the back of the tank with clear silicone.

There is a box on the outside of the tank held by 2 bulkheads. It uses 4 drains.

The water level is set by the weir teeth on the box and not the holes.

On my 75 I have 3 holes in the tank. The 1.5 inch for the overflow box and 2 holes for 3/4 inch returns.

For a 75 gallon tank you are going to want an overflow rated around 800-1200 gph with at least 2 drains.

 

[kdx7214]

Thanks for the information! I found it on BRS and will be ordering the 1000gph this week. Cheers!

Here is a complete overflow. It happens to be the one I use on my 75 gallon tank. It is rated for 800gph.

The box inside the tank is held by the bulkhead. There is no glue.
It comes with
1x 1.5" Transfer Bulkhead

2x 1" Drain Bulkheads

1x Red PVC Standpipe

1x Drilling Template

1x 60mm Holesaw

In the kit
There were several brands of overflows. I am not sure what is available now.

You do not need any fancy piping inside the rear box. You only need a standpipe in one of the 2 drains. The other drain is just a bulkhead with a valve on that drain. SO forget about the herbie and durso and all that.


Here is what I use on my 240. It is glued on the back of the tank with clear silicone.

There is a box on the outside of the tank held by 2 bulkheads. It uses 4 drains.

The water level is set by the weir teeth on the box and not the holes.

On my 75 I have 3 holes in the tank. The 1.5 inch for the overflow box and 2 holes for 3/4 inch returns.

For a 75 gallon tank you are going to want an overflow rated around 800-1200 gph with at least 2 drains.