I've had the WD-G2MRNR-W ( G2MDV7G02219) system for about 3 weeks now and making a thumping sound maybe once a day. Last Friday I call your customer service dept. and talked to a gentleman and he couldn't give me a reason for the noise. He said it might need another pump for an additional $ 30.00. I need to know if this will fix the problem and do I need to hire another plumber to install this device? Do you have any referrals for a plumber that has installed your units and is reasonable? Your instruction manual doesn't say anything about this problem. I need some help on this matter as I'm on a fixed income and times are tuff. Sincerely, Larry Lukowski