Hi all
Putting together my 125, and 40b sump, and was doing some calculations regarding overflow capacity in case of return pump power loss and backsiphoning etc.
I understand the rational of drilling a hole in the return plumbing, about a half inch below the water line to prevent excessive backsiphoning into the sump. However, in running the numbers, and thinking through the location of the hole, isn't it the depth of the overflow teeth (or smooth weir, if so inclined) that ultimately sets the amount of water that drains back to the sump? On my 125, if I have 3/4 inch water level above bottom of teeth, that's 4.2 gallons heading back into the sump via the overflow box in the 'forward direction'
If I put my syphon break hole 1/2 inch below the surface - that's 2.8 gallons backsiphoning through the pump. But the other 1.4 still goes into the overflow box.
If your hole is above this level, sure, once air gets in, it'll break siphon going backwards through the pump, but water (1.4 gallons in this case, for a total of 4.2) is still going to go into the overflow box and into the sump in the 'forward direction'.
Doesn't this mean then, if your returning outlet is above the lower level of your weir, the hole is pointless? Since the outlet itself will suck air before the weir finishes draining water into the overflow box?
The hole really only comes into play if your outlet is below the weir/teeth, and even then, only really is useful if it is below the level of the weir, since any water above that is heading in the normal direction anyway (over the weir and into overflow box).
It seems to me that, Essentially, I should calculate overflow capacity as a function of weir depth and tank dimensions, and as long as my return outlet is above my weir/ teeth, the hole and backsiphoning volume are irrelevant.
Or am I going wrong somewhere?
Thanks fir any insight!
Sent from my iPhone using Tapatalk
Putting together my 125, and 40b sump, and was doing some calculations regarding overflow capacity in case of return pump power loss and backsiphoning etc.
I understand the rational of drilling a hole in the return plumbing, about a half inch below the water line to prevent excessive backsiphoning into the sump. However, in running the numbers, and thinking through the location of the hole, isn't it the depth of the overflow teeth (or smooth weir, if so inclined) that ultimately sets the amount of water that drains back to the sump? On my 125, if I have 3/4 inch water level above bottom of teeth, that's 4.2 gallons heading back into the sump via the overflow box in the 'forward direction'
If I put my syphon break hole 1/2 inch below the surface - that's 2.8 gallons backsiphoning through the pump. But the other 1.4 still goes into the overflow box.
If your hole is above this level, sure, once air gets in, it'll break siphon going backwards through the pump, but water (1.4 gallons in this case, for a total of 4.2) is still going to go into the overflow box and into the sump in the 'forward direction'.
Doesn't this mean then, if your returning outlet is above the lower level of your weir, the hole is pointless? Since the outlet itself will suck air before the weir finishes draining water into the overflow box?
The hole really only comes into play if your outlet is below the weir/teeth, and even then, only really is useful if it is below the level of the weir, since any water above that is heading in the normal direction anyway (over the weir and into overflow box).
It seems to me that, Essentially, I should calculate overflow capacity as a function of weir depth and tank dimensions, and as long as my return outlet is above my weir/ teeth, the hole and backsiphoning volume are irrelevant.
Or am I going wrong somewhere?
Thanks fir any insight!
Sent from my iPhone using Tapatalk
