Help! I have spent a lot of money on my plumbing problem and still don't have an answer. We added a 2bedroom 1 bath addition onto our house. About a month after we started using the addition we began to have a sewer smell coming from the cold water. We removed alloy rod from water heater just in case-no change. All pipes are pvc. Paid a plumber to come out and he filled all pipes in the entire house with chlorine which had to sit for 8 hours. Then we flushed out the entire house. That got rid of the smell for 2 days and then it was back. I have asked everyone and no one knows what to do. We are on city water and do not have any problem in the original house. Only have smell in sink and bath cold water of addition. It lasts for about 1-2 minutes then goes away. Can you help?