I have a new gunite, salt water pool, and, since it was started, there have been bubbles spitting from the first pool return. I, and my pool builder, were concerned about a leak in the system. However, my PB now says that, after a thorough review of the system and researching the issue, he believes the spitting bubbles are hydrogen created by the SWG and that nothing further can be done to prevent it. Is he correct? The spitting is loud and annoying. How can I be certain it is not caused by a leak, preferably before I make final payment to the PB?