I have a 125K BTU gas fired hydronic heating system in my house. My water is very hard. Over the past 15 years of opening the system to add zones, the boiler appears to have hard water issues. As it heats up, the boiler make loud kettling sounds. I have flushed the system, but that only has a minimal effect. I was told it needed to be flushed with muriatic acid. I procured a pump, fill tank and all of the needed hoses. I have plumbed over a drain and a fresh water supply line. My question is what % solution of acid should I use, how long should I recirculate and will the impurities pass through the boiler outlet spigot? Any info you can share I would appreciate. I also bought a supply of baking soda to neutralize the acid. I know this is a job for a professional , but in these troubled economic times sometime we have to do for ourselves.. Thanks

First rule to follow

Wear long rubber gloves and full goggles for your eyes. safety glasses will not protect your eyes. the acid can splash up under the safety glasses.

ACID is dangerous to work with so have a fresh water supply available at all times and if you have a spill or get it on you flush with fresh water right away.

Now on with the show.

Safety data sheet READ

http://www.boilercleaning.com/pdfs/HydrochloricAcid.pdf

NEVER POUR WATER INTO ACID. While this acid could possible be poured eighter way I preferr not to take the chance.

Are you using swimming pool grade acid?

I need to know this or does the bottle have a % grade of acid label?

Sorry about all the questions BUT acid can be a very dangerous to use.

I believe it is a 30% solution. I purchased it from Lowe's...
Thanks