Installing an internal overflow ?
- Thread starter SFish
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RedStangGA
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Are you making your own overflow box or do you have one in hand already? And I'm assuming you are planning on drilling the back or side of the tank instead of the bottom?
RedStangGA
New member
Rimmed or rimless tank? Either way you will need to decide approximately where you want the water level for the tank and then place the overflow a bit lower. How much lower will depend on the size of the overflow and how much flow you will be putting through it.
I know that's a vague answer at best lol! In my case, my 220 has trim around the top so I wanted the water level to be just at or above the bottom of the trim so it won't be visible. I went with a relative small, 22 inches wide, overflow as I am not planning on too much flow from the return pump so I placed mine so that the rim of my overflow(which is toothless) just below the trim level of the tank. This is to allow for the slight rise in water level above the level of the overflow. If your overflow has teeth, you'll want to take into account the bottom level of the teeth, not the top, as I'm sure you don't want water going completely over the top of the fixture but rather through the teeth. So you'd want the top of the teeth just above where you want the waterline. Place the overflow in place with that in mind and then mark your hole locations.
Please keep in mind I've done one tank this way! Hopefully someone who has dome multiple tanks will chime in too.
I know that's a vague answer at best lol! In my case, my 220 has trim around the top so I wanted the water level to be just at or above the bottom of the trim so it won't be visible. I went with a relative small, 22 inches wide, overflow as I am not planning on too much flow from the return pump so I placed mine so that the rim of my overflow(which is toothless) just below the trim level of the tank. This is to allow for the slight rise in water level above the level of the overflow. If your overflow has teeth, you'll want to take into account the bottom level of the teeth, not the top, as I'm sure you don't want water going completely over the top of the fixture but rather through the teeth. So you'd want the top of the teeth just above where you want the waterline. Place the overflow in place with that in mind and then mark your hole locations.
Please keep in mind I've done one tank this way! Hopefully someone who has dome multiple tanks will chime in too.
Just remember when u are drilling for your bulkhead that they have a minimum distance of 1 hole diameter from the edge of the tank to the hole & inbetween multiple holes. So if u are drilling a 60mm hole it has to be atleast 60mm from the top of the tank glass to the hole. If u are drilling more then one hole u would need atleast 60mm inbetween holes. If u are drilling a 45 mm hole then it would be 45mm.
When I come out the back of the tank I like to stay close to the minimum distance so the water level inside the overflow box is high enough to where u don't have water coming over the overflow box and falling down more then a couple inches to the water level inside the overflow box because it will be loud, like a waterfall coming into the box. If u drill the holes to low in the back of the tank the water would be dropping down to far & be loud.
As far as the overflow box itself, I would probably just place it at the bottom of the trim but it's really kinda hard to say with out knowing more on the setup. The higher the flow the higher the water level will be up on the teeth of the box. Spacing on the teeth will also affect this so it is hard to say how much higher then the bottom of the teeth the water level will be. How most of the premade boxes are made they are meant to go to the bottom of the trim & that will keep the water level above the trim when u are looking from the outside of the tank so u can't see the water level when u look at the tank.
So basically u would want the bottom of the teeth to be close to level with the trim on the outside of the tank. If it's a little lower u will probably still be ok because the water level will build up on the teeth atleast a small amount.
When I come out the back of the tank I like to stay close to the minimum distance so the water level inside the overflow box is high enough to where u don't have water coming over the overflow box and falling down more then a couple inches to the water level inside the overflow box because it will be loud, like a waterfall coming into the box. If u drill the holes to low in the back of the tank the water would be dropping down to far & be loud.
As far as the overflow box itself, I would probably just place it at the bottom of the trim but it's really kinda hard to say with out knowing more on the setup. The higher the flow the higher the water level will be up on the teeth of the box. Spacing on the teeth will also affect this so it is hard to say how much higher then the bottom of the teeth the water level will be. How most of the premade boxes are made they are meant to go to the bottom of the trim & that will keep the water level above the trim when u are looking from the outside of the tank so u can't see the water level when u look at the tank.
So basically u would want the bottom of the teeth to be close to level with the trim on the outside of the tank. If it's a little lower u will probably still be ok because the water level will build up on the teeth atleast a small amount.
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