Pipe freezing

[jeffg]

There seems to be a difference of opinion on just how cold it has to get for pipes to fail. Weather Channel claims an outside air temp of 20F or less is required for it to be a problem (see http://www.weather.com/activities/homeandgarden/home/hometips/severeweather/pipefreeze_prevent.html), while the most conservative formula used by the National Weather Service to determine hard freeze warnings is 28F or lower for five hours or more. Just from a limited amount of experience I think the NWS advice is closer to the truth but I'm wondering if anyone else has info or opinions about it.

While researching we discovered that pipe failure is not caused by the force of expanding ice against the walls of a pipe, but water/air pressure between multiple points of freezing along the pipe, or (more commonly) a single point of freezing and valve. As ice in a pipe expands, the still liquid parts become more and more pressurized. This is why little or no ice is usually seen at breakage points, and it's also why leaving taps barely open, even if it's enough to hear air escaping instead of water (i.e. barely a drip), is enough to relieve this potential pressure buildup and prevent failure, even if the entire pipe eventually freezes over.

 

[alr2903]

Jeff, I believe everything you posted is true. One wild card is in older homes/ or homes with additions after the main house was constructed. I drip the taps in our bathroom, a very long run of pipe, to be on the safe side. This particular run of pipe is in a non heated crawlspace. I have covered the "vents" to the crawlspace until we get back to ususal temps next week. One of the variables is the plumbing goes under some rooms that we heat but do not keep toasty warm in severe cold weather. Also how many people are in the house? Using bathrooms during the night is a variable. When in doubt drip the faucet. If you need a plumber for a freeze issue half the city will also need one. Arthur

 

[whirlcool]

Here in Texas our plumbing usually runs in the attic. We have one very long run on which I've installed that heated gutter tape. When the attic temp drops to 32F the heater tape automatically comes on.

We did have a pipe freeze in our last house. It froze in the elbow of a 90 degree turn. Fortunately the leak was only a slow drip. Maybe about 18oz of water on the floor each day.

Now a neighbor was out of town and had a pipe freeze and burst over their living room. There was water coming out of the house from under the front door for a few days. We finally called the water company to turn off the water to the house. The people returned two weeks later to a flooded house. They literally had to strip out the entire interior and start over again.

We learned whenever we go out of town we always turn our water off to prevent things like this from happening.

 

[arbilab]

"Here" in Texas is a government building built to the lowest/cheapest standards that met code. As a result, parts get rebuilt every other year because a 2" sprinkler pipe freezes in an unheated foyer and floods 2/3rds of the first floor.

With the ice storm, I talked to the maintenance guy. Space heaters would preclude the problem, but they are prohibited. Opening the lobby 'security' doors to the foyer would preclude the problem but would require hiring a temporary security guard. HUD will pay $50,000 to rebuild the first floor but not a cent for loss prevention. Oh, and the damage mitigation requires hiring security guards for WEEKS (instead of hours for prevention) while the sprinkler system is out of service.

Government wisdom, your tax dollars, blahblahblah.

 

[circlew]

Sounds to me they should have the sprinkler company install a dry-pipe system in the unheated portion of the building.

 

[arbilab]

This maint guy has been here 5 years and seen it happen twice.

For the 16 times that's going to happen in the 40-year projected life of the building and what it costs to fix when it does, a dry-pipe system would have cost LESS. Or howzbout heat tape and a freeze stat the LAST time they rebuilt it? Nope, strictly lowest bidder, both the engineering and construction. Thinking is not in the budget.

Another thing that happens here--probably not ONLY here--is designing insulation and HVAC to Chamber of Commerce averages rather than to extremes that are known to occur regularly. Such that when summer gets predictably hot, AC can't keep up and when winter gets predictably cold, heat can't keep up and plumbing can't reliably survive.