Sump size and overflow box

[Charney]

I have two questions here. First how do you determine how much water the sump should be able to hold if you lost power/pump failure?

Second with the U tube type overflow boxes like the eshopps is it possible to prevent them draining your whole tank and not loosing siphon if the power is lost?

 

[duanes]

With overflow boxes, they will only drain the tank until the water stops flowing thru the weirs, usually only a few inches.
I have some sumps that I run very close to full, and the power occasionally does out, and the sumps do not overflow.

here is a weir box which fits inside the tank, if the pump stops pumping water to the tank, water only flows to the sump until tank level levels out at the bottom of the weirs.
The weirs are the notches in the box, the Utube is 1.25" inner diameter.

 

[Charney]

Thank you for the post. lots of good info. I get that the tank will level off at the bottom of the weirs. When this happens does the Utube drain the rest of the water in the box and then break siphon? Or if the end of the tube outside the tank is submerged will it retain the water?

thanks

 

[fishguy306]

No, the over the back overflows are designed so that water will remain in both boxes as well as the U tube to keep the siphon, water just will not be flowing in either direction.

 

[Charney]

ok great thank you

 

[ShadowStryder]

Something else to consider which some forget or are not aware of is with the return. When power goes out there is a siphon that can drain back through the return and drain all the way down to the pump and into sump. If you have the return outlets fairly low it can drain all the way down to the return outlet.
You can counter this by drilling a small hole in the return outlet an inch or so below the water line.
When the water level hits this it breaks the siphon.

As for as leaving room in your sump for power outage, you can either do the math or just test how much room you need by turning power off and letting it drain until it stops. The just leave that much room in the sump.

 

[Charney]

Something else to consider which some forget or are not aware of is with the return. When power goes out there is a siphon that can drain back through the return and drain all the way down to the pump and into sump. If you have the return outlets fairly low it can drain all the way down to the return outlet.
You can counter this by drilling a small hole in the return outlet an inch or so below the water line.
When the water level hits this it breaks the siphon.

As for as leaving room in your sump for power outage, you can either do the math or just test how much room you need by turning power off and letting it drain until it stops. The just leave that much room in the sump.

Thank you great insight

 

[duanes]

My overflows never back siphon, because I always put the return above the surface level of the sump water line. This is also known as a siphon break.