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A New Boiler

How to correctly install a water-pressure reducer

Richard Trehewey holds a toilet

I have an 1893 home that has gravity-flow hot-water heating. I bought a new boiler. The maximum rating on the boiler is 15 psi and the pressure at the water supply is 65 psi. How do I correctly install a water pressure reducer? Books at the library are missing any mention about pressure reduction and back-up prevention.

— Jeff


Richard says: First of all, it is with some sadness that I hear an old gravity-style heating system is being replaced. I'm all for new technology but there is something special about the simplicity of those systems. No pump, no electricity, quiet, comfortable and obviously reliable. Having said that, time marches on. To make a new boiler safe, you need a lot of things, including a pressure-reducing valve. A pressure-reducing valve takes incoming city or well-water pressure (45 to 60 pounds pressure) and reduces it to a preset 12 pounds, which it automatically maintains inside the heating system. The pressure can be manually raised if the building is taller than 20 feet above the boiler. When you heat water, it needs to expand. The old boiler probably had an overflow/expansion tank in the attic, which looked like an old toilet tank. This has to be removed, capped and a special pressurized expansion tank must be added in the basement. A safety relief valve also has to be added to keep a boiler from becoming an unguided missile. I can think of entry level plumbing and heating people that could mess this up. You're not doing this work yourself are you? Call a trusted, tested professional to do it right.


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