When the ejection pump is ejecting water/waste from the pit, it makes a loud clunking noise upon completion of pump cycle. Could there be air in the line or is there something else.

Hi Phyllis:

That noise is the CHECK VALVE... see image below. The typical check valve installed in these ejector systems can be a bit noisy, to say the least.

You can order a quieter check valve and get it installed... should reduce the noise quite a bit. Check them out here:

A.Y. McDonald Mfg. Co. : Plumbing : Sump & Sewage Check Valves : Sump & Sewage Check Valves

Another kind is the SILENCER check valve:

Amazon.com: 1-1/2" Silencer Sump Pump Check Valve: Home Improvement

Back to you...

MARK