Frozen Heating Pipes


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Old 01-10-15, 02:54 PM
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Frozen Heating Pipes

Here are additional thoughts on frozen water pipes.

Since water expands as it freezes, it can produce enormous stresses in pipe. These will be in the form of hoop stress, which tends to put the circumference of the pipe in tension. If the pipe wall splits, it can lead to a flood when the ice eventually thaws.

Copper pipe is particularly prone to splitting open longitudinally. The split may open up for several inches or more. Steel pipe is much stronger and more resistant to splitting. PEX piping has relatively low pressure ratings but it's toughness may help resist rupturing.

The biggest risk is flooding. This is particularly true if the valve from the domestic water supply to the boiler's pressure reducing valve is open when the pipe ruptures. The risk is worse if the house is left unattended during bitterly cold weather.

But shutting the valve from the domestic water supply then presents the concern of the boiler draining below the safe operating level and then firing - which is particularly the case if the boiler does not have a low-water cutoff to shutdown the burner.

Personally, I would not leave a house with hot-water heat unattended for very long during winter weather. Best to always have an astute, handy person visit the house daily. Alternatively, antifreeze could be added to the system, but that is a messy proposition and may present future disposal problems.
 
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Old 01-10-15, 04:08 PM
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All good recommendations , I thought that the antifreeze we use in boilers is non toxic, and shouldn't be a problem. My only complaint with the antifreeze is, it will leak from the pressure relief valve after a couple of years. Heating systems along with all the domestic piping should be checked once in a while . When I leave home for more than a day, I close the water supply.
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Old 01-10-15, 04:32 PM
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Propylene glycol, typically used for boiler antifreeze, is not harmless and most municipal wastewater utilities prohibit its discharge into sewers. So, what are you going to do with it? From the USEPA:

Propylene glycol is also toxic and combustible and can react with other chemicals. It requires
proper storage and handling. Eye contact should be avoided by wearing proper eye protection
whenever it is handled.
Both ethylene and propylene glycol are water soluble. Improper disposal results in the
contamination of drinking water, groundwater and land surfaces. Fish, aquatic animals and
people can be poisoned.
 
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Old 01-10-15, 04:33 PM
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I have antifreeze in my boiler and to prevent it from being deluded by fresh water in, I installed a domestic pump switch that has the low pressure shut off feature that interrupts power to burner if the water pressures drops below 9 psi . Cost is under 50 dollars and is well made.
 
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Old 01-10-15, 04:53 PM
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my boiler and to prevent it from being deluded
I don't think any of us would want our boilers to be deluded!

You need a new spell checker I think!
 
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Old 01-10-15, 05:08 PM
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If my climate and my frequency of leaving the home unoccupied necessitated using anti-freeze in a hot-water boiler, I would sooner have a forced-air furnace. Comfort-wise, and for other reasons, I would prefer hot-water heating, so I wouldn't be tempted to rip out a hot-water boiler solely to avoid using anti-freeze. But I might avoid purchasing a house that I thought I would have to use anti-freeze in.

I do my own maintenance on my boiler system, such as replacing or adding valves, fixing leaks; maintaining the pump, the relief valve, and the expansion tank, etc. Such activities would involve messing with and getting smeared with anti-freeze. Being sprayed by water is bad enough.

By the way, discharging waste anti-freeze into a septic system is not recommended.
 
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Old 01-10-15, 05:37 PM
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Additional comment:
If I didn't have a neighbor to check the house daily while I was gone, I would get my regular mechanical/plumbing guy to do it, and loan him my house key. My guess is that he would offer to do it for free, but I would insist on paying him.
 
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Old 01-10-15, 08:02 PM
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In a former life I used to do maintenance on smaller hot water systems. One in particular had two 1.2 million BTU/hour boilers and the system was filled with a propylene glycol mixture. At least the designer/contactor was smart enough to install a make-up tank and pump along with piping the safety valve discharge back to this make-up tank. Down side is that the way it was set up the make-up pump couldn't return any fluid to the system.

I saw no reason whatsoever to have this system filled with anti-freeze, first because it rarely gets down to freezing in this area (maybe once every ten or twenty years) and secondly, if the heating system crapped out during such a freeze the company would have a whole lot more problems than just a frozen coil or pipes.

Had a few other similar systems and removed the anti-freeze from then all.


Now of course there ARE areas where anti-freeze IS necessary for any of a number of reasons. But the system MUST be designed from the get-go for this and include such items as the make-up tank and pump as well as various freeze-stats and alarm systems.
 
 

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