There is water hammer in my in law's home how do I clear it up by draining the lines when they have a steam heating system

Actually most steam systems are self draining by the return loop that goes back to the boiler so the hot condensate water can be reheated to make more steam.

When you mention water hammer, are you sure that it is in the heating system, or (most likely) in the potable water. Please let me know exactly what is happening, when are you getting the hammer?

The water hammer occurs when the boiler is turned on tried to drain potable water system shutoff main water valve to house. Opened water valves upstairs in sink and downstairs in basement. Closed water valves opened main water valve. Opened water valves water returned to system. But shortly water hammer returned probably need to drain boiler not sure ho to.

What ever you do stay away from removing the water from the Hartford loop or make sure of the water level before firing the boiler back up after draining. That keeps the water level safe in the boiler so it does not dry fire and go BOOM.

You need to determine if your inlaws steam heating system is a one-pipe or two-pipe steam heating system. Most homes tend to have a one-pipe steam heating system.

A two-pipe steam heating system has a radiator steam trap on one side of the radiator and a radiator valve on the other. The radiator valve simply opens or closes the supply of steam to the radiator. The radiator steam trap is a thermostatically operated automatic valve: It closes to prevent steam from leaving the radiator and opens to allow the condensed steam (water) to leave the radiator and return to the boiler, where it is once again turned into steam.
If the steam traps have not been repaired (the internal thermostat replaced) in the last 5 to 7 years the steam traps are most likely failed open and causing your water hammer.

A one-pipe steam heating system has an air vent located on one side of the radiator and a radiator valve on the other. If water hammer is occurring it may be time to replace the air vents on the radiator and the main air vent located near the end of the steam main in the boiler room.

Visit www.StateSupply.com for additional information and the replacement components needed to get rid of the awful water hammer banging!

Good Luck,
StateSupply

Water hammer can also occur when you have problems with the pitch of the pipes feeding the radiators. All pipes in a steam heat system need a slight pitch downhill in the direction of the boiler. If they are not pitched right, water will pool up in sections that don't fully drain cooled water all the way back to the boiler. That water cools when the boiler isn't under steam, then when the boiler next makes steam, and the new steam reaches the section of pipe that is pitch wrong and has standing water in it, the new steam superheats that standing water, causing it to expand very rapidly. The sudden vaporizing of the standing may be what is causing the hammering sound you are hearing. We had two sections of pipe like this in a 100 year old 30 building. One section was fixed by insulting it. Our other problem pipe had to have the pitch angle of the pipe adjusted. It's amazing what 1/2" in pitch can do - and how much it can cost to fix!