Turning off water to house with baseboard heat and gas boiler

December 23, 2015 6:16 AM

We bought a 60-year old house in the Hudson Valley this summer and we're about to leave on our first vacation. The house has hydronic baseboard heating and a very old gas boiler. The forecast looks warm: If I switch off the heat at the thermostat, can I then safely turn off the main water to the house? What would happen if I left the thermostat set very, very low with the main water off?

Bonus question: We also have a gas-fired hot water tank. Can I turn off the main water, and just turn the heat way, way down?

posted by oddovid to Home & Garden (11 answers total)

Why do you want to turn off the water?
posted by Chocolate Pickle at 6:27 AM on December 23, 2015 [6 favorites]

This is a bad idea. Just leave the heat on. Especially as you haven't done a winter in this house yet.
posted by JPD at 6:33 AM on December 23, 2015 [3 favorites]

People that have these systems usually try very hard to keep the house heated when they are gone, and some even install alarm systems to alert someone if the house goes below, say, 40 degrees. The reason for this is if an old hot water heat system freezes, even a little bit, you can easily have $30k-$60k in damages to replace the frozen system, boiler and all radiators. And sometimes insurance won't cover it.

When a house with similar systems is left for a whole winter season, sometimes they are winterized meaning all of the water is blown out of the whole system and the house has no heat at all until the system is refilled. It's hard on a house to sit cold, plaster can crack and weird things can happen. The other danger is if any water is left in the system, it will freeze and cause damage, usually to the boiler, which would probably be ruined by any amount of leftover water.

If this were my house, I'd put the heat at 60, install an alarm to alert neighbors if it goes below 50. Since the boiler is old and might fail having a smart plumber drain the system for $500 is some good insurance.
posted by littlewater at 7:24 AM on December 23, 2015 [1 favorite]

I'm guessing that you want to turn the water off to avoid water damage in the event that a pipe or the boiler breaks.
The hydronic system should be ok with the water off. It has an expansion tank, an overtemp switch, and an overpressure relief valve.
I think it's fine to turn the water off, set the thermostat to 50 degrees and turn the water heater down to the lowest temperature.
I think your only worry is if the temperature gets to zero or below you might have frozen pipes when you get back.
posted by H21 at 7:47 AM on December 23, 2015

Call someone in your area who services such things and ask. If you are going to be gone less than a month, I'd leave the system running.
posted by amanda at 7:51 AM on December 23, 2015 [2 favorites]

I get the sense from the wording of your question that you are confused about how your home systems work so let's break this down step by step.

1. I live in your area. The 10 day forecast has no temps below freezing until NYE, when the low will be 27 overnight (inside your house will not get nearly so low). So in that sense it is safe to turn off the heat if you are leaving for Christmas/New Years. I would generally advise leaving the heat set to 50 since it is safer and you never know if you will be delayed returning home.

2.) It's always a good idea to turn the water off at the main while you are gone. Your hydronic system is a closed loop, if it regularly needs make up water you have a leak with accompanying damage accumulating. I leave my make up water valve off all the time, I would rather be alerted to a leak by the low water alarm turning off the boiler than by flooding. With that said, when you leave during truly freezing weather, you need a way to monitor the temperature in your house, whether electronically or via a friend or neighbor.

3.) Same with your hot water heater, it is monitored by sensors and if it is losing water via a leak then it will shut off.
posted by no1hatchling at 8:21 AM on December 23, 2015

I live near you in a house almost as old. If you are only going to be gone a week, I would just leave everything alone. Older houses in the northeast seem to frequently have odd, delicate, byzantine systems rigged up over the generations to keep everything functioning. If you start shutting things down, it may cause problems when you really need them to start working again.
posted by freakazoid at 8:30 AM on December 23, 2015

Response by poster: Thanks to all...yes, thought to turn off water to head off some freak pipe bursting. And yes, still learning how systems work. (Specifically, I suppose, needed to know if the heating system is closed loop). A neighbor will be checking mail/keeping an eye on the house. We'll be gone 10 days.
posted by oddovid at 8:38 AM on December 23, 2015

I always turn the water off at the street when we leave for extended period because I don't trust the pipes either.

Just throw the breaker on the hot water tank and you'll be fine.
posted by humboldt32 at 10:05 AM on December 23, 2015

Yeah, I was told to turn the hot water tank off at the breaker if I wanted to turn the water off at the street when I left my house for the whole of this month. Little did I know it would end up being summer temperatures while I was gone, but whatever.
posted by Stewriffic at 12:48 PM on December 23, 2015

Turning the breaker off only works with electric tanks, oddovid has a gas tank.

The gas should be turned off at the tank using the gas valve on the tank set at vacation or pilot. That way the pilot will stay lit if you have one and the line won't have to be bled. You need to do this in case a leak drains your tank the gas doesn't come on.
posted by Mitheral at 12:57 PM on December 23, 2015 [1 favorite]