Can anyone tell me what the black tube here(see image below; small hose is highlighted by yellow) between the pipp leading to my filter and going to the return plumbing is? Note that there is a solar heater going up to the roof on the top right(in case it's something for that). I was guessing some bleeder hose of some sorts, but I can't find anything online about it...
I can hear some air escaping when the pump is on where this tube connects to the return plumbing, and I'm not sure if this is a leak or a function.
Thanks.