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how to limit the chance of flooding with a HOB over flow and sump

Goonie

CCA Members
how would I need to run this so I wouldn't have to worry about either the tank or sump from flooding due to lost syphon or power outage?
 

Becca

Chairpersons
Staff member
Add a siphon break to your intake and keep your outflow high up in the tank. I only ever fill my sump that isn't plumbed directly to a drain about 1/3 so there's room for water in case this happens.
 

Andrewtfw

Global Moderators
Staff member
Putting a small hole on the underside of the u-tube that is under the waterline in the tank will solve the problem of the tank causing the sump to overflow, so long as the sump can accommodate a little extra water.
 

Goonie

CCA Members
I run my 125 a couple inches shallow that should be enough room to accommodate the water from a wet/dry filter right ? Tank already has a fx6 and large sponge but i tend to over filter things
 

Becca

Chairpersons
Staff member
I run my 125 a couple inches shallow that should be enough room to accommodate the water from a wet/dry filter right ? Tank already has a fx6 and large sponge but i tend to over filter things
The 125 doesn't have to accommodate the extra water, the wet dry does, unless you're doing a dump filter (over the tank) and not a sump?
 

Goonie

CCA Members
I was thinking running a hob over flow into a 40b either as a wet dry or a moving bed.

If if has water and looses siphon what waters left in the sump would still return to the tank, hence the need for head space.

Loose power keep syphon tanknwoukd drain until siphon brakes( the hole would fix that issue)

Unless I'm completely missing something, which i could be, as I haven't run a sump before.
 

JLW

CCA Members
Honestly, I would never, ever, ever run a tank with a hang on overflow box. They're way more trouble than they're worth. Overtime, bubbles accumulate in the U tube, and unless you're good about purging them, you'll get reduced flow and all sorts of problems. They're incredibly noisy, they're unreliable, and they're not particularly efficient. You'd be far better off drilling the tank.

The big fear with a hang on overflow isn't usually that the power will fail and the sump will flood -- we know how to deal with that. Syphon breaks in the return, plenty of head room in the sump. The problem is that the U tube can fail, and you then pump the sump into the tank with no syphon down, and it overflows the tank. Been there, done that. :)

There's a couple of ways to go around this. You can put the pump on a float switch which will turn it off if the level in the tank gets too high, or if the level in the overflow box gets too low (depending on which type of float switch you get). You should throw out the single giant U tube that they give you, and replace it with 2-3 U tubes, and religiously purge them of air. A redundant one ensures that if something clogs it, you'll have less of a problem. (You can also add a second overflow box). Beyond that, its just a regular, religious check of the U tube for any obstruction, and removal of air bubbles. And living with the fact that it may eventually fail.
 

Freakgecko

CCA Members
Honestly, I would never, ever, ever run a tank with a hang on overflow box. They're way more trouble than they're worth. Overtime, bubbles accumulate in the U tube, and unless you're good about purging them, you'll get reduced flow and all sorts of problems. They're incredibly noisy, they're unreliable, and they're not particularly efficient. You'd be far better off drilling the tank.

The big fear with a hang on overflow isn't usually that the power will fail and the sump will flood -- we know how to deal with that. Syphon breaks in the return, plenty of head room in the sump. The problem is that the U tube can fail, and you then pump the sump into the tank with no syphon down, and it overflows the tank. Been there, done that. :)

There's a couple of ways to go around this. You can put the pump on a float switch which will turn it off if the level in the tank gets too high, or if the level in the overflow box gets too low (depending on which type of float switch you get). You should throw out the single giant U tube that they give you, and replace it with 2-3 U tubes, and religiously purge them of air. A redundant one ensures that if something clogs it, you'll have less of a problem. (You can also add a second overflow box). Beyond that, its just a regular, religious check of the U tube for any obstruction, and removal of air bubbles. And living with the fact that it may eventually fail.
Can also use aqualifters continuously running up into the U Tube(s) with airline tubing in order to keep air bubbles from forming. I agree though, HOB overflows are a nightmare from my experience. So much so that I traded a sump for a couple crappy canister filters (although I do slightly regret that, now that I have a tank drilled with a corner overflow)
 

JLW

CCA Members
A proper overflow is definitely the way to go for the best tank experience, but hang ons are not ... proper overflows. :)

For the record, I'd probably never run another tank with a corner overflow, either.
 
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