Answer:

I am not sure if this is a pool or hot tub but some issues would be common to both. First, you may be right about the air being sucked through the pump, but this is less likely since it is on the suction side. Are you also seeing excess air on the return side? You are more likely to see that on the return side. There are a couple of other possibilities. You may have a crack in one of the pipes, likely on the suction side of the system allowing air in. You may also have low pressure at the filter, meaning it may require cleaning or maintenance. Last idea, if you have a salt chlorine generator, you may be seeing a byproduct of the chlorine generation.