When away for a week, okay to shut off main water and leave boiler and HW on?

Howie718

I have another post about my failed floodstop shut off valve. I may not be able to remedy that before heading away for the holidays. I'll be away for 6 days next week. Would it be okay to shut off the main water valve in the house, yet leave the hot water heater and boiler on? I wasn't sure if that would cause any issues that I would regret when back home. I do have a whole house water softener, that I suppose I will need to turn off so it does not attempt to regenerate.

Thank you, Howie

pecmsg

Can the house freeze without heat?

Big Ed_4

You can shut off the hot water heater if no one is there to use it . The boiler would be ok if there are no leaks . Working in the industry I would be concerned if the boiler did not have a low water cut off for safety .

WMno57

What I have:

• Cast iron forced hot water boiler with no LWCO
  
• Electric resistance 40G tank water heater
  
• Well
  
• Water softener
  

What I do when I go away in winter:

• Power to well - Off
  
• Power to water softener - Off
  
• Main water valve for house - Off
  
• Power to water heater - On (Legionella)
  
• Valve to water for boiler - Off
  
• Boiler is on to heat the house
  
• I do not drain any pipes
  

Valve to water for boiler is off when I'm home as well. I only add water in the fall when I maintain the compression tank, and maybe a little at the end of heating season.
Dry firing my boiler if I had a massive hydronic system leak might damage the boiler. Would it burn down the house, or would the basement just get warm? I'm trying to avoid creating a steam explosion by watering a red hot boiler. That would be catastrophic. Water supplies, well or municipal, can not be assumed to be constant. I could have a power outage for my well. Dan has a story here somewhere about a municipal water outage that caused a boiler explosion.

Jamie Hall

Is there a working low water cutoff on the boiler? If so, close the manual valve on the makeup water line and turn off the rest of the water to the house.

ethicalpaul

Your concern about legionella...who is keeping it out of the pipes that supply your house from your well?

seized123

WMno57 said:

no LWCO ...

Valve to water for boiler is off when I'm home as well. I only add water in the fall when I maintain the compression tank, and maybe a little at the end of heating season.
Dry firing my boiler if I had a massive hydronic system leak might damage the boiler. Would it burn down the house, or would the basement just get warm? I'm trying to avoid creating a steam explosion by watering a red hot boiler. That would be catastrophic. Water supplies, well or municipal, can not be assumed to be constant. I could have a power outage for my well. Dan has a story here somewhere about a municipal water outage that caused a boiler explosion.

@WMno57 I was hoping you could explain the above a little more, I'm having trouble understanding it.

I don't have an LWCO on my oil boiler hydronic baseboard system (actually I don't know what they look like but I haven't seen anything on the boiler that I think would be one) but I keep thinking I should get one. Am I correct in assuming you don't have one, not because you just haven't bothered to put one in but because you think it might contribute to the bad scenario you mention? If so, why?

When I go on vacation in winter I have been turning the well off and closing the whole house shutoff valve but leaving the boiler on. But then it occurred to me: if a leak sprung in the heating system and water drained out and the boiler water wasn't replenished because I turned off the well and the boiler kept firing ("dry firing?') that would be very bad; and an LWCO would shut down the boiler, which seems like a good thing.

Could you make clearer the exact scenario you're talking about, what exactly would have to happen (re: well outages, hydronic leak, possibly the action of an LWCO) to get that "dry firing" and/or "watering a red hot boiler" you talk about. I'm sure your reasoning is sound, but I'm just not getting the picture (and also want to make an informed decision about getting an LWCO, and also want, like @Howie718, to know what I should be doing on vacation in winter.)

WMno57

Great question Paul. Almost everyone's immune system can deal with the small populations of Legionella that may occur naturally in groundwater. The problem occurs when they are allowed to explosively multiply, by housing them in an environment that is ideally conducive to their replication. 90 - 108 F. If a water heater is shut off for a week, there will be two time periods when the ideal growth range exists.
https://en.wikipedia.org/wiki/Legionella#Heat

Temperature affects the survival of Legionella as follows:
Above 70 °C (158 °F) – Legionella dies almost instantly
At 60 °C (140 °F) – 90% die in 2 minutes (Decimal reduction time (D) = 2 minutes)
At 50 °C (122 °F) – 90% die in 80–124 minutes, depending on strain (D = 80–124 minutes)
48 to 50 °C (118 to 122 °F) – can survive but do not multiply
32 to 42 °C (90 to 108 °F) – ideal growth range
25 to 45 °C (77 to 113 °F) – growth range
Below 20 °C (68 °F) – can survive, even below freezing, but are dormant

My parents were micro-biologist public health scientists. Growing up, we had strange but interesting dinner conversations. Occasionally, Dad would get an after hours phone call from work about some local food poisoning case. Mom did home canning. Everything she cooked was well done. Eggs, Roast beef, etc.
I hope everyone has a great holiday. Remember food safety. Keep hot foods hot and cold foods cold.

Howie718

Thank you all for the responses. I will turn off the softener and the main water supply. My boiler does have a LWCO. Happy holidays! Howie

WMno57

I don't have an LWCO because I haven't bothered to put one in.
Dry Firing and Steam Explosion. Separate and mostly unrelated problems.
I see no real downside to having or adding a LWCO. They are a must for Steam because water is lost out the vents. Most if not all hot water boilers today have them. I have an old boiler, it never had one. For me, not having one is not a big deal. If I dry fire my boiler, that will probably damage the boiler. Burn the house down? Unlikely, but possible. I guess I'm betting any leaks that might develop will be small and discovered before the whole system runs dry. I have a high volume system.
Adding water to a dry red hot boiler will create an explosion. Water expands 1700 times in volume when it turns to steam.
I don't think there is only one way to shut down a house. It depends on the house, anticipated weather, and the owners tolerance for risk.
An extremely unlikely scenario would the simultaneous combination of a large leak, intermittent water outage, and LWCO failing open. The perfect storm.

Howie718

I am actually more concerned about the hot water heater than the boiler. The failed floodstop valve is after the manual shut off. I could just shut the cold supply to the hot water heater. Do i need to worry about turning down the temp on the HW heater if I do that?

Howie

seized123

Thanks @WMno57, all is clear!

Jamie Hall

There seem to be two threads going here at once? One on shutting off the water and one on Legionella? On the shutting off the water -- yes, shut off all your domestic water, close the manual feed on the boiler, and turn off the power to the water heater. No need to drain anything. Since you have a low water cutoff, @Howie718 , that will take care of the possibility of the hot water heating springing a leak and draining and damaging the boiler.

And a commnet for @WMno57 -- a dry fired boiler, depending on its clearances to combustibles, can burn the house down given enough time.