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PLUMBING SYSTEM INSPECT DIAGNOSE REPAIR
ANTIFREEZE for BOILERS
BACKUP PREVENTION, SEWER LINE
BLOCKED DRAIN REPAIR METHODS
CLEANOUTS, PLUMBING DRAIN
CLOGGED DRAIN DIAGNOSIS & REPAIR
FREEZE-PROOF A BUILDING
FROST HEAVES, FOUNDATION, SLAB
HEAT TAPE USAGE GUIDE
HOT WATER HEATERS
INSULATION INSPECTION & IMPROVEMENT
NO HEAT - BOILER
NO HEAT - FURNACE
ODORS GASES SMELLS, DIAGNOSIS & CURE
OIL FIRED WATER HEATERS
PIPING IN buildings, Clogs Leaks Types
PLUMBING FIXTURES, KITCHEN, BATH
PUMPS, PONY PUMPS
RELIEF VALVE LEAKS
SEPTIC SYSTEM INSPECT DIAGNOSE REPAIR
SHUTOFF VALVE LOCATION, USE
SUMP PUMPS GUIDE
TRAPS on PLUMBING FIXTURES
WATER HEATER PROBLEM DIAGNOSIS
WATER HEATER COMPARISONS, PROPERTIES
WATER, WELLS, WATER TANKS: TESTING GUIDE
WATER SHUTOFF VALVE LOCATION, USE
WATER SHUTOFF VALVE, WELL PUMP
WATER SOFTENERS & CONDITIONERS
WATER SUPPLY & DRAIN PIPING
WELLS CISTERNS & SPRINGS
WINTERIZE A BUILDING
How to protect building drains from freezing: this article explains how to prevent frozen drain piping and freeze-damage or burst drain pipes in buildings and in the building connection to a septic system or to a municipal sewer line. You might think that because plumbing drains slope downwards (or should) that there is not freeze risk - that's not entirely true, as we explain here.
The articles at this website will answer most questions about freeze protection for piping and other building plumbing and heating system components: how to winterize a building to avoid frozen pipes, and how to thaw frozen water supply & drain piping, wells, & water tanks.
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Our page top photo shows what might happen if a building drain is clogged, leading to standing wastewater in the pipes which then froze and burst.
Is the building heat going to be left "on" or "off" - the answer determines the extent of freeze-proofing needed.
What? My Building Drains Can Freeze Too?
Freeze damage risk in buildings is not confined to water supply piping or hot water heating piping. Building drains can also freeze and break, including fixture traps and building drains.
Building drains can freeze inside the building and even outside a drain line that is not below the frost line can easily freeze in some conditions which we outline below.
Even if the building water supply piping has not frozen a drain line can freeze. You may first notice the problem when a toilet, sink, or tub simply stops draining.
In a building where water is left on at some plumbing fixtures, be sure that there are no leaky supply valves or running toilets.
In freezing weather a slow drip or water running slowly into a drain pipe can lead to ice build-up, a frozen or even a frozen and burst drain pipe, or a water backup into the building.
What Causes Building Drain Pipes to Freeze?
Handling Roof Gutters that Drain into the Sewer Piping
Some older homes include roof drainage downspouts that are carried to drain pipes which connect to the building sewer drain piping. In some installations the gutter downspouts connect to a drain line inside the building, perhaps running out of the building under the basement floor onwards to a public sewer line.
Such drains can easily freeze in an un-heated home, leading to broken drain lines, frost-heaved basement floors, and severe basement flooding.
We recommend that drain connections between roof gutters and downspouts and the building sewer line be abandoned.
If necessary, install temporary above-ground downspout extensions to conduct roof runoff well away from the building rather than into the sewer line via the basement floor. Incidentally, because the volume of roof runoff sent into a sewer line can overwhelm municipal sewage treatment plants this connection is prohibited in some communities.
What Else to Do to Avoid Frozen Building Drains
Reader Question: What is the required or recommended depth for connecting house drain pipes(such as a bathroom waste pipe) to a septic tank to avoid freezing?
What is the required or recommended depth for connecting house drain pipes(such as a bathroom waste pipe) to a septic tank in New York State in order to avoid freezing?
Reply: House drains may be above the frost line and depend on proper slope and drainage to avoid freeze-damage.
Plastic drain pipes are usually buried at least 18" and bedded in sand to avoid mechanical damage to the pipe. But building main drains (upper right circle in our photo at left) are often not below the frost line outdoors and in a freezing climate such as New York, the lines depend on proper slope to drain into a septic tank or into a municipal sewer main to avoid freezing.
So the waste piping depth is more determined by using the required pipe slope (1/8" to 1/4" per linear foot) and working backwards from the septic tank or municipal sewer line connection point and the property's own elevation and slope.
Our sewer piping photo (above left, courtesy Galow Homes - click to enlarge) shows a new sewer line (at left and foreground) being connected to an existing house drain (circled areas) in a New York home. You will notice that where the existing main sewer line exits the building the plumber included a cleanout (upper circle in photo) and that the depth of the waste piping is just about 12" below the ground surface. At this particular installation the drain piping slope exceeds 1/4" per foot in the area of the new connection because the ground slope in this area falls rapidly away from the home.
From the point of entry into the septic tank or into a municipal sewer main, drain piping lines need to slope 1/8" to 1/4" per foot to drain properly. Some piping sections may slope more than this due to terrain properties (our photo above) but slope should not be less.
If the outside (or inside for that matter) building drain piping is not properly sloped it will clog.
Reader Question: how much does it cost to bury a pipe below the frost line
Wonderful information. I am currently in the process of buying a home in Virginia, and a portion of the drainage pipe is exposed. Any idea how much (typically) it would cost to bury the pipe, or who I would contact to fix this? - Meaghan 5/31/12
if the drain pipe that is exposed is properly sloped and you don't have fixtures that run continuously into it (say a running toilet), the freeze risk is very low, especially in VA.
Speaking very generally, the 2013 cost to dig a 25-foot trench runs between $300. & $400. or about $13. to $16. per foot, with of course many variables such as depth, soil properties, and obstructions. There are online cost estimators that take your zip code and will give closer estimates, but even those can be way off as the cost estimator has no idea about local site conditions at your property. Simply hitting a big boulder, for example, can change the picture.
The cost to bury is something you'd best get from a local excavation contractor or landscaper who can see the actual site conditions, length of pipe to be covered, to what depth, thus estimating yards of soil, hours of machine and labor time, and finish landscaping requirements.
Without that data, an estimated cost to bury something arbitrary. Just be sure that your "burying" does not also bury building siding or you'll be asking for an insect problem.
Reader Question: what is the frost line depth in Nebraska's Platte Valley
Any idea what the specs might be in Nebraska's Platte River Valley? We are not far to ground water. - Gary 8/16/2012
Reply: easy to find frost line data for Colorado, but for Nebraska?
Gary, The spec is the frost line, right? Any local plumber will tell you. From a quick historical search about the frost line in Nebraska I learned from the Colorado Climate Center that for Colorado the frost line data is:
Typically the frost line in Nebraska in your area is around 10-14-inches from the ground surface
The deepest frost penetration in Nebraska in the last 20 years was at 20-inches. But watch out: more extreme variations are occurring in weather patterns everywhere so deeper frost penetrations may be in store.
In the 1930's in a cold winter with little snow cover the frost line extended down to 30"
So to be safe, and if you plan to move to Colorado, assume the frost level there is at least 20-inches and 30-inches would be safer. OK, let's look for a better answer.
Take a look at the Air Freezing Index to Guess at Frost Line Depth for Your Area
Can we translate that data to Nebraska? Not directly. When you cannot find local frost line depth data, building codes adopted by your community still will have the answer. For example, the International Residential Code (IRC) for 2012 gives Air Freezing Index data for each U.S. state.
Figuring the Frost Line Depth for Nebraska
Most of Nebraska has an index of 1500 or less, except for Boyd, Burt, Cedar, Cuming, Dakota, Dixon, Dodge, Knox, Thurston counties where the air freezing index is 2500. Now we can do a little extrapolation and arm-waving:
The same IRC explains in Table R 403.3(1) that we can translate an air freezing index into a required footing depth. That data is in our table quotation just below. You can see that for an air freezing index of 1500 or less the minimum footing depth is 12-inches, and for an air freezing index of 2500 you'd have to make the footings at least 16-inches deep. Not very deep, right? Since the intent of footing depth is to protect a footing from frost heaves, I figure this is a good approximation of the frost line depth for your area: 12-16-inches.
Watch out: local frost line data and local codes prevail; rules about minimum building footing depth, which you can use to guess at a safe frost line, may be different in your area from those assumed by and in the area addressed by teh IRC. Best bet is to ask your local building department.
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