How to Convert a Steam Boiler to Hot Water

While many people enjoy steam heat, the technology is old and you may want an updated system. Depending on the building, a hot water system may be more efficient, thus saving you money. You can convert your steam heating system to hot water, but be prepared to overhaul the entire system.

Things You'll Need

• New Boiler (or do fabrication work to the old one)
• Compression Tank
• New Piping
• Plumber's Tools
• Basic Knowledge of Plumbing

Instructions

1. Do a heat-loss calculation.

   Before converting your steam system to a hot water setup, do a heat-loss conversion calculation for your home. You want to find out if your new hot water system (which operates at a lower temperature than a steam system) will be sufficient to heat your home in the same way that the steam system currently does.

2. Check for leaks.

   You're going to need to check for leaks before converting to a hot water system. Since a hot water system runs on a higher PSI than steam, turn the pressure on the boiler system up to 10 PSI. It normally runs about 2-3 PSI for steam, but with the increased pressure you are going to walk around the house checking for leaky plumbing before starting the conversion. Be sure to follow the plumbing and check every single joint and connection for leaks.

3. Fix any leaks.

   If/when you find any leaks, you'll need to replace that section of pipe or replace the joint with one that can withstand the higher pressure. It's probably a good idea to make sure that you are using at least 1/2" pipe throughout your new system (unfortunately, if the old system does not meet these specs, you should probably replace all the piping). With 1/2" piping, you should be able to achieve a flow rate of 1 1/2 gallons per minute (gpm) of hot water which would translate into roughly 15,000 BTUH which should be sufficient to replace the old heating system and still keep the rooms in your home comfortable in the dead of winter.

4. Decide what to do with the boiler.

   If you are going to keep the old boiler, you'll need to change the trim, ditch the gauge glass, get rid of the low-water cutoff, remove the pressuretrol and near-boiler piping. If you are getting a new boiler, all you'll have to remove is the near-boiler piping.

5. Use a good air separator.

   You'll need a compression tank. But, you'll need to figure out - based on your old system - how much water you have pumping through the system now. Talk to the company you are buying the compression tank with. Since this is a steam to hot water conversion, you are essentially building a custom set-up so do not rely on the "by the book" compression tanks for traditional hot water systems that are built from the ground up.

6. Controlling the system.

   You will probably need to use a continuous circulatory with an outdoor air reset controller. This will be the most effective way to control your new system which is, in reality, a hybrid steam system converted to run a higher pressure hot water system.

Tips & Warnings

• You must do the "leak test" before doing the conversion. You do not want to get your new system set up and find out that every join and connection leaks.