Question regarding sump pump discharge pipe having secondary pipe

[UNC054]

So I'm wondering the purpose of the secondary J-shaped pipe exiting above ground on my sump pump discharge pipe.

Reason I ask, every once and a while I notice its wet and water had came out of it at some point during the day. I does not happen very often as I've filled the sump crocks up with five gallons of water to try and replicated the exit point, but it was coming out the end location of the discharge pipe as usual and not the J-shaped pipe.

I do have two sump pumps, each with their own check valve that come to a Y and then lead out to the main discharge pipe.
The J-shaped above ground pipe is approximately 30" or so after the Y occurs. I was able to find another photo of a J-shaped pipe online (3rd pic) so there must be a reason for it.

Just curious if the occasional water exiting is okay or should there be concern to follow-up on it.

Any feedback with be appreciated.

 

[fsdork]

Not a plumbing expert, but just looking at it logically - if the secondary outlet is at a considerably higher elevation than the main discharge (ex. pic 3), its purpose is to discharge water when the main discharge is unable to clear itself quickly or completely enough - rather than allowing backup into the sump. I would suspect a blockage in the main pipe, downstream of the secondary - or a shift in grade whereby the slope of the main discharge line flattened out (or sagged/kinked mid-span). A far less likely alternate cause would be someone having swapped in a monster pump that pushes way more volume than the system is designed for.

 

[crashz]

Its a vent / vacuum break. The pump will discharge but when it stops the siphon it creates must be vented in order to avoid damage to the check valves. Depending on the flow and discharge pipe length it might burp a little when the pump kicks on too.

 

[JohnnyG]

crashz got it right, the little bit of dripping that you noticed is likely just evaporated moisture condensing and dripping, unless the downstream pipe becomes restricted for short periods.