3/4" drains for a 220?

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Dis

Dis

Dovii
MFK Member
Oct 22, 2010
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Hamilton, ON
Looking into getting a 220 gallon, it has two holes drilled for 3/4" bulkheads in each overflow. Is this enough flow for this size tank?

The overflow are in the corners of the tank and these two holes are the only ones in the overflow. Thanks for any advice
 
So a single 3/4" in each or 2? If a single, just add a 1" or 1 1/2 if there is room. If there is 2 3/4" holes I would cut them larger, but doing it without the ability to drill a pilot means you will need to run your drill extremely slow.
 
Can you add bigger holes and use those as your return lines? I did that on a 120 that I had some years ago. I had to notch out the overflow to run the 3/4 inch lines over it and still fit under the glass tops though.
 
The size of holes really depends on the amount of flow, for the kind of fish. If you are going to have fish like discus that don't appreciate lots of water flow, 3/4" should be fine. If you are thinking rheophillic such as Theraps species then 3/4" might be too small. One size does not fit all.
I have always kept riverine species that require more flow so 1.5" is the smallest I'd go with, and 2" is even better, and because I've always kept lots of plants, which can easily plug up small bore, the bigger the better.


The above is 1.5", and I was lucky to catch it in time, or I would have had a flood.
 
It depends on the flow you want. Each 3/4" drain is capable of flowing about 330gph of gravity fed draining. This means that you can technically flow about 660gph through them, which is a turnover rate of about 3x per hour. However, at that flow you have no safety factor in case one of the drains gets clogged. I like to have at least 2x the draining capability as the flow in the tank. This means that if one drain gets clogged, the other can still handle the flow. With that in mind, you probably shouldn't flow more than 330gph through them, that way you have a safety margin in case of a clog.

For example, I am going to run three H2Overflows, each capable of flowing 1,200gph, on my 220. I am planning to run about 1,500gph of flow through it, but I will be capable of flowing 3,600gph. This way, if one of them becomes clogged I can still handle the full 1,500gph. Now, if two get clogged at the same time, I'm SOL.
 
Thanks for all the replies, really helped out. I haven't seen the tank in person and by the pictures the overflows do look larger. After a bit of research it seems that 3/4 is way too small for this size tank. Thanks again
 
Seems like they are 3/4" overflows. Both overflows flow down through a stack of bio balls and into the bulk head, there is no standpipe or durso. Does this increase the flow?
 
If I want a higher flow in the tank I will just use a powerhead. I'm hoping the hole size isn't a deal breaker? The price is right for the tank but I want to make sure I'm getting something th hat I can use.

I'm planning on some plecos and a group of kelberis
 
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