Modify HOB Overflow

[KreativJustin]

Hello everyone,

I'm looking & hopefully buying a 75g with a sump this weekend. It has one of the older style J-hook HOB overflows on the back. Has anyone modified these to make them more like CPR HOB overflow? I really don't want to throw in another $80-150 on a CPR HOB overflow if I can modify the J-hook style, but I really do not want a bunch of water on my floor.

Any help is appreciated, thanks in advance!

 

[Andy Sager]

Hello everyone,

I'm looking & hopefully buying a 75g with a sump this weekend. It has one of the older style J-hook HOB overflows on the back. Has anyone modified these to make them more like CPR HOB overflow? I really don't want to throw in another $80-150 on a CPR HOB overflow if I can modify the J-hook style, but I really do not want a bunch of water on my floor.

Any help is appreciated, thanks in advance!

I think it will depend on what filter ( brand and model number) you are getting and by what method the water is returned to the tank. If it is a pump driven return, you'll need have a constant supply of inbound water. If the pump pulls water into the filter box, there may be a way.

 

[KreativJustin]

It is one of the old school traditional styles..

https://media2.cdn.bulkreefsupply.c...11-eshopps-pf-800-overflowbox-plumbing-an.jpg

It'll siphon from tank into HOB overflow -> flow to sump -> return via pump

 

[Andy Sager]

It is one of the old school traditional styles..

https://media2.cdn.bulkreefsupply.c...11-eshopps-pf-800-overflowbox-plumbing-an.jpg

It'll siphon from tank into HOB overflow -> flow to sump -> return via pump

Unless you are willing to have a hole drilled into the tank, I think you are going to have to use this as is. If you drill a hole towards the top of the tank, the water will naturally fill the sump when the return pump fills the aquarium. I'd use at least a 1" through hole fitting but would depend on the flow rate of the sump pump. You can always go bigger ( i.e. 1 1/4"-1 1/2" fittings) if the pump is oversized.

 

[KreativJustin]

Well, would drilling a hole in the top of the tube and use an aqua lifter like the CPR style does to help the siphon when the power goes back on from a power outage.

 

[Andy Sager]

Well, would drilling a hole in the top of the tube and use an aqua lifter like the CPR style does to help the siphon when the power goes back on from a power outage.

From the picture you posted, there is no need to break the siphon because when the power goes out, the main tank will only go down as far as the bottom of the slots at the top of the black box. If you break the siphon in the J tube, when the power goes back on, your tank will flood since the water has no place to go. With the power off, the water level in the tank and the overflow will equalize so no water will be flowing. When the power goes back on, the flow will automatically start again.
What I was talking about was drilling a hole in the aquarium to be a direct overflow line so there would be no need for the Eshopps overflow box.