Swimming pools blog

I am a new inground pool owner. I have a two speed pump. When the
pump is on low, after a few hours, small air bubbles come out of
some of the pool returns, not all of them. When the pump is
switched to high, large amounts of air come gurgling through most of
the returns for about a minute and then there is no problem. Is
this normal? I can find no leaks. However, when the pump is on
low, if you trace the path of the water you can actually hear water
trickling at the return lines. in other words you don’t hear this
noise until after the the water passes through the pump,filter, and
then heater. the noise seems to start after the Bioguard Mineral
Springs unit which is just before the return lines. The pool
installer said that the filter may create air when it gets dirty and
that as long as there wasn’t air coming through the returns when the
pump was on high then everything was normal. Does anyone have any
ideas? Does anyone know if the Mineral Springs unit creates air

when it sanitizes the water?
thanks