Steam Boiler False Water Line

False Water Line

When you are replacing an old boiler with a new higher efficiency boiler you may encounter water level problems, water hammer, short cycling and even flooding. When you change the old boiler, usually the new boiler is shorter. This normally gives us a false sense of security that the A dimension will be correct.

When we lose our "A" (drawing) dimension we will encounter problems. When changing a steam boiler it is a good idea to keep the water level close to where the old water level was. This is especially true when your system has a dry return, steam pipes run in a crawl space, or the old boiler, was in a pit and you bring the new boiler out of the pit.  A wet return can also create problems if the wet return goes uphill from the boiler towards the end of the steam main and has a short vertical rise between the return and the steam main. Any radiator returns that drop down to a wet return must stay wet or the radiators with the new dry returns will stop heating. A simple rule is what was wet before should remain wet when the new boiler is installed.

A false water line will create a water line similar to where the old boiler normal water level was while the new boiler water line is where it has to operate. In a sense the system will now have two water levels. The system and boiler water levels which could be very different.

Here is a list of rules we need to follow when piping the false water level;

1. Equalize the top of the "U-seal" back to the header
2. The return should be connected to 4" below the horizontal pipe of the "inverted-U
3. Keep the vertical pipes to the inverted "U" close together as you would with a Hartford  loop
4. Keep the pressure low. Do not exceed 1.5 psi cut-off. In all steam systems today the lower we can run the pressure the better providing the system still heats well.
5. Install a good air vent on the inverted "U" pipe. It should be at least 12" or more from the "U" pipe.
6. You may encounter some water hammer until the pipes fill with water.

Disclaimer: The information found on this website is for informational purposes only. All preventive maintenance, service, installations should be reviewed on a per job situation. Any work performed on your heating system should be performed by qualified and experienced personnel only. Comfort-Calc or it's personnel accepts no responsibility for improper information, application, damage to property or bodily injury from applied information found on this website as it should be reviewed by a professional.