Hey everyone! Have a question about my 33 year old hydronic (closed system) hot water boiler. I have taken good care of this system in it's lifetime. It heats well and quickly too. Flush every year, bleed all air, inspect all parts and replace anything that is not up to snuff. The last few years the boiler has started to pop when running or "kettle". I tried flushing it out with boiler cleaner that I brought at Home Creepo. It will quiet down the unit for a few weeks, but then the noise starts to return slowly once again. I know I am going to replace the whole unit sooner or later. Just trying to get as much time out of it as I can. Has anyone had this problem with their boiler? Thanks in advance for any suggestions! 