Blowing bubbles ... I mean, bubbles blow.

[DJ88]

Tony,

I'd look for small holes in the return lines allowing air to get in. The faster the water is being pushed past the air hole the faster air gets sucked in and more bubbles are created.

Most likely a PVC joint. BUt possibly the pump connections.

With that said.

My return drops donw into one 45, then a second to make the 90 deg turn easier then straightens out then into an upwards facing 45 again. So basically it goes through 135 degrees of turning. The last 45 is at the water line in the sump. I get a bit of a burping noise from time to time but that is it.

hth