Overflow Box and Overflow Box Plumbing Options

[ReefDreamz]

I am planning to have a custom tank built with dimensions in the ballpark of 49.5"x31"x22", about 145 gallons. I am trying to decide between having 2 or 3 drains, having 1 or 2 returns and going with an external overflow box or an internal overflow box. My overflow will be plumbed through the floor to a basement sump. I would like the back of the display tank to be as close as I can get it to the wall so if I went with an external box there wouldn't be a lot of room to mess with the plumbing after the tank is full and moved into place. What would you choose in this scenario? Adding further confusion, I have seen overflow boxes plumbed with durso style standpipes, some with just a strainer on the standpipe, and some external overflows with just bulkheads and no standpipes at all. How do you know which to choose?

 

[Montiman]

A lot of this is personal opinion so I will try to be fair while telling you what I would do.

External Overflow boxes give you more room in the tank but also mean the tank needs to come out further from the wall and can make the plumbing under the box difficult to work on. Additionally I have had tank manufactures tell me that they believe an internal is more structurally sound long term than an external.

Unless you must have the external for aesthetics, I would go internal. Better structural reliability fewer potential locations for a leak and you can back the tank against the wall like most people want to. If I had a fish room behind the tank I would go external because I could better access the plumbing and I could cut through the wall so the tank could still sit flush.

As to 1, 2, or 3 drains. The fewer drains the simpler with fewer leak locations if you are an inexperienced plumber. The more drains the more redundancy in case 1 drain fails. No matter what I would do at least 2 drains for a Herbie style overflow. With 2 drains you can use one as a full siphon controlled by a gate valve and the other as a slow trickle drain. There are many videos on this drain style that explain it well. This method is far far far quieter than a single durso style drain and for this reason alone I would use at least 2 drains. In a 3 drain or bean animal set up the only difference is the third drain is an emergency overflow drain in case the first 2 drains clog.

I am personally not a fan of this style of drain as I think it adds more complexity with more potential leak areas. It is more reliability but my preferred method of increasing reliability is to just use bigger pipe. I have seen lots of 3/4 in drains clog a couple 1in clog but never a 1.5in or 2 in drain. My personal preference is to just go with bigger pipe but fewer lines if you are worried about something clogging. On your size tank most would use 1in drains. If you are concerned about clogging I would use 2, 1.5in drains.

 

[dhnguyen]

OR have the best of both worlds and get one of these shadow overflows



I personally dislike the traditional internal overflows because they take up so much room inside the tank that would otherwise be used for aquascaping and corals.

The eshopp doesn't take a lot of room in the back. Only 3 inches.

 

[ReefDreamz]

A lot of this is personal opinion so I will try to be fair while telling you what I would do.

External Overflow boxes give you more room in the tank but also mean the tank needs to come out further from the wall and can make the plumbing under the box difficult to work on. Additionally I have had tank manufactures tell me that they believe an internal is more structurally sound long term than an external.

Unless you must have the external for aesthetics, I would go internal. Better structural reliability fewer potential locations for a leak and you can back the tank against the wall like most people want to. If I had a fish room behind the tank I would go external because I could better access the plumbing and I could cut through the wall so the tank could still sit flush.

As to 1, 2, or 3 drains. The fewer drains the simpler with fewer leak locations if you are an inexperienced plumber. The more drains the more redundancy in case 1 drain fails. No matter what I would do at least 2 drains for a Herbie style overflow. With 2 drains you can use one as a full siphon controlled by a gate valve and the other as a slow trickle drain. There are many videos on this drain style that explain it well. This method is far far far quieter than a single durso style drain and for this reason alone I would use at least 2 drains. In a 3 drain or bean animal set up the only difference is the third drain is an emergency overflow drain in case the first 2 drains clog.

I am personally not a fan of this style of drain as I think it adds more complexity with more potential leak areas. It is more reliability but my preferred method of increasing reliability is to just use bigger pipe. I have seen lots of 3/4 in drains clog a couple 1in clog but never a 1.5in or 2 in drain. My personal preference is to just go with bigger pipe but fewer lines if you are worried about something clogging. On your size tank most would use 1in drains. If you are concerned about clogging I would use 2, 1.5in drains.

Thank you so much for your input. This is very helpful. In talking with the custom tank builder (Coast to Coast in NJ) he also recommended going with 2 1.5" drains. Another difference between the external and internal overflows is the location and number of return holes. The internal overflow has one return hole in the overflow which splits to two nozzles. The external overflow setup has two return holes in the back wall of the tank, one on the either side.

 

[ReefDreamz]

OR have the best of both worlds and get one of these shadow overflows



I personally dislike the traditional internal overflows because they take up so much room inside the tank that would otherwise be used for aquascaping and corals.

The eshopp doesn't take a lot of room in the back. Only 3 inches.

This style of overflow is nice but I don't see the point since the return lines need to be plumbed into the back of the tank with 90s and so they will end up sticking out further than the slim overflow box making its slim design kind of pointless. I agree with you about disliking the internal overflows. I think the extra space in the tank and the professional look is worth the downsides of more failure points and having it further away from the wall.