Question about Hot Water Heating System

Can I turn off the water main if we aren't home for a couple of weeks in the winter?  It's a sealed system and it seems that I should be able to. I set the thermostat at 60 degrees and the water heater to "vacation." 

Thanks.

I am not a plumber.

I say yes  -  w/ precaution of bleeding/draining some water from pipes, once main shut off. In case some pipes close to exterior walls froze in cold snap. Especially as thermostat will be lowered to 60.

Did I mention I'm not a plumber?  Though weakly considering becoming one.  Highly lucrative, given SO/MA clientele/mindset. Seems easy to exceed the low ethical standards I've seen in the profession locally ( namely: the two Ronnies).

Cramer - tell me more about the "vacation" setting - what brand/model. I don't have similarly labeled on my rudimentary model.

dickf3 - Thanks for the feedback.  I had to go down to the basement to check my water heater. I was thinking about another water heater I had that had a "vacation" setting. The one that I have now is a Bradford - White and I turn the setting to "Pilot" when we're away. (I don't turn it to "off" because I don't want to have to light it when we get back.) 

I probably set my thermostat closer to 62 - 64. I do have one pipe in the basement that goes to the washing machine which is on an outside wall that does freeze unless I let the utility sink faucet drip. Last  winter, when the outside temperature was freezing, I let the utility sink faucet drip and no problems. 

eta - I let the faucet drip all winter. It was a cold winter. 

Of course if I turn the water main off, I won't be able to let the faucet drip. I would make sure that all of the faucets and toilets have been emptied of water. 

I'm pretty sure you're talking about two different systems.  Your water heater with the vacation or Pilot setting is for domestic hot water - showers and sinks.  The heat in your home is different.  If the home-heating system fails for any reason, your pipes can freeze regardless of the temperature setting on the water heater.  How is the house heated? If it is steam or hydronic and relies on influx of fresh water for any reason, you should leave the water main on.  

Red-Barchetta  - Yes, I'm talking about two different systems. I just threw the hot water heater in there because a) I always turn it to "pilot" when we're gone for more than a couple of days, and b) comments on message boards say that if the water main is turned off, the water heater should be turned off, regardless of the type of heating central heat. 

The house is heated by a hot water heating system (separate from the water heater)  with radiators and unlike steam, does not rely on the influx  of fresh water. It's a sealed system. 

I'm pretty sure that I can turn the water main off, but was just trying to see if there is any problem with that.  I'm going to ask one of the plumbers or the HVAC company that services the boiler. My recollection is that when I asked several years, I could not get an unqualified answer - there was always a "you probably can, but...."    

I just spoke to the HVAC company and they said that I should keep the water main on. Even though  it's a sealed system, if for any reason the pressure drops, the boiler will need fresh water.  He convinced me.

I've been leaving the water main on for many years when we're away, and will continue to do so.

Sounds reasonable to me.  If you have isolation valves on the risers going upstairs you can shut those.  A frozen/burst pipe in the basement is much less trouble than one on the second floor. 

When we leave our house, we set the thermostats to 50ºF.

HVAC people don't know anything about hot water (hydronic) heat. 

Many people (service/install techs) like to shut the incoming water to a hydronic heating system after it is filled and purged with air. One benefit is that a break in a pipe, a freeze-and-burst for example, will be limited to leaking only the water above that height in the system as opposed to a constant leak as the system tries to replenish itself due to the drop in pressure.

Shutting the incoming water to the boiler or the main water valve are the same thing for the purposes of this conversation.

master_plumber - Thanks for the feedback.