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Boiler Operation During Water Main Break

FordGoo Member Posts: 2
Hello to all,

I have just been advised of a municipal water main break in my area and there is no water supply to my house. At the moment it is cold where I live. I have a gas-fired Super Hot Saturn Series boiler and it heats my house through coil furnaces that blow air over the hot water coils. 

When I moved in here, I was advised by the tech that did my HVAC inspection that even if I was going out of town for a few days, I would not want to shut off the water to my house, as the boiler requires a certain supply of water to operate properly. Now that the main break has happened, which is essentially the same scenario as turning my water main off, are there any steps I should take to make sure the boiler doesn’t end up damaged? It could be 48 hours or longer before the main in the steeet is repaired. As far as I can tell there’s a pretty complete set of sensors on the boiler. 

Any help is appreciated!


  • psb75
    psb75 Member Posts: 754
    You are probably ok for 48 hours--IF your boiler is filled and has no leaks-- it needs no new water. During this time of 'water outage' make sure your boiler pressure doesn't go DOWN. It should be around 12-18 psi. Most hydronic heating systems have an automatic water fill set-up. The boiler will take in water only if it needs it. It is NOT GOOD if a boiler is taking in regular doses of new water. That means "something is wrong."
  • Zman
    Zman Member Posts: 7,493
    Closing the isolation valve between the domestic and boiler water will assure that a faulty backflow device wont allow boiler to depressurize.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • FordGoo
    FordGoo Member Posts: 2
    Thanks to everyone who replied for these comments. The pressure appears normal (16 PSI) and I have closed the valve from the domestic supply to the boiler while they fix the break. Regards
    JUGHNE Member Posts: 10,897
    My first home boiler was installed about 25 years ago.
    At that time the supply house said that the PRV (fill valve) had a check valve in it to prevent back flow.

    A water main situation such as yours proved that theory wrong.
    Main repairs required draining the main down....it also then pulled some of my boiler water out.

    Since then I have double backflow checks, leave the supply off and have a LWCO added to the system.
    EBEBRATT-Ed Member Posts: 14,472
    Prvs have a check valve inside them or at least they don't allow backflow that does not mean they are 100% tight though
    JUGHNE Member Posts: 10,897
    300' of 6" main draining out apparently creates enough syphon action to pull water out.
    Boiler in basement; floor about at bury point of water main....6' or so.
  • Lance
    Lance Member Posts: 257
    This is one reason I recommend low water cutoff for hydronic boilers. I had an apartment complex client whose maintenance employee drained the boilers for the summer. He started up two dry boilers in the fall. When the tenant felt the boiler wall too hot to touch, fire dept was called. Could not turn off boilers as gas valve stuck open from the heat. Had to turn off the gas. We installed two new boilers with LWC.