Sump chamber *actual* water depth

[EricDP]

While testing flows in my new sump (1st time building a sump) I noticed the water height was higher on the upstream side than the baffle itself. When the pump is stopped, it settles about 1/8" high, and when the pump is on, it sits about 1/4" high. I attribute this to surface tension. And note that I'm currently testing with fresh water. As I understand it, salt water has different surface tension. How much different might it be?

 

[Red_Beard]

Negligibly different.

 

[EricDP]

Okay, thanks. Good to know.

I find it interesting that I haven’t seen this mentioned after reading quite a few threads about sump design. Am I just trying to be too accurate with my depths? For my build, my main overflow drain is hard-plumbed into my ATS, which makes it difficult to raise or lower the ATS. So I want to ensure the water is optimal depth in that chamber.

 

[BryanM]

Okay, thanks. Good to know.

I find it interesting that I haven’t seen this mentioned after reading quite a few threads about sump design. Am I just trying to be too accurate with my depths? For my build, my main overflow drain is hard-plumbed into my ATS, which makes it difficult to raise or lower the ATS. So I want to ensure the water is optimal depth in that chamber.

I think this just depends on the needs/requirements of each persons setup.

I have a surf4 ATS, and it just floats in the sump, so my height doesn't matter all that much.

 

[Red_Beard]

Once your baffles are in, the only thing that is going to change that height in any chamber other than the return is going to be flow. You could calculate that based on volume(area) required to support the flow. Fixed width x variable height=gpm at 0psi

 

[EricDP]

Fixed width x variable height=gpm at 0psi

This is pure gold.

I had originally estimated that my flow would be just under 250Gph. Width is 11-7/8” (it’s a 20 long). I measured the water height above the test baffle at 5/16” when the pump was running.

11-7/8 x 5/16 ~= 3.71Gpm or 222.6Gph.

I love it when the math matches the observation. :)

 

[Red_Beard]

Algebraic brother, that is friggin mathmatical! :)