Decided to drill my tank

[Easto]

I've been looking into it.

I would be drilling the back of the tank.

I am just not too sure why the siphon drain in a lot of the pictures I have seen have a 90 degree fitting pointing down.







I don't understand why that is needed and how do you purge all the air at the start to begin the siphon.

[target]

With the 90 pointed down you get a full flow syphon as the pipe will begin to draw water once the level in the overflow raises high enough. The water falling pulls the air with it, and purges the air that way. A small air bubble will be left at the top of the piping but most of the air will be purged.

[Doug]

Many of the online stores sell packages, matching the bulkheads to the hole saw.

[CM125]

its pointed down to get the siphon lower in the chamber, its not needed, but helps a bit with the restart.

[Easto]

Would something like that second picture be fine?

I was looking at a 6 ¼”W x 4”D x 5”T Overflow box.

How much space should I have between the bottom of the box and the opening of the siphon intake?

[CM125]

Should generally aim for about 6" between the siphon tube and the overflow, less will work but can be harder to tune and will take longer to recover on restart (this is why people use turned down elbows, to get the siphon tube lower). The second picture would work, but if you can get more height I would go for it

[CM125]

http://gmacreef.com/herbie-overflow-...method-basics/

[Easto]

I was thinking about drilling near the Middle of the overflow Box height. Then putting the siphon tube with the elbow facing down. I haven't measured but I'd think that would give 1.5" - 2" between the siphon and the bottom of the box, which sounds like it's fine.

The second one I'd drill at the same height but turn the elbow up facing.

[CM125]

I would try to get more space then that, even if you add some pipe on the top or bottom, it will fluctuate a lot in the beginning and its nice to have that extra. since you have the option I would definitely do it.