There aren’t many things more horrifying than starting a load of laundry in your washer and watching — (and smelling!) — raw sewage come up through your basement floor drain.
Unfortunately, that’s exactly what happened to Emily R. on an early Sunday afternoon in February 2014.
After several frantic calls to local plumbers, Emily was advised her sewer line had probably frozen somewhere between the house and the city main. She was also advised to stop all water use in the house and wait till Monday morning for a plumber to jet out the line.
A Homeowners Worst Nightmare
The winter of 2014 was especially cold in the upper US and Canada. The frost line dipped as low as 7 feet in some places. The uncommonly deep frost caused hundreds of water and sewer lines to freeze and some to break from the long and brutal cold snap (http://www.thegazette.com/2014/02/10/frigid-temperatures-bringing-frozen-waterlines-to-many-eastern-iowa-communities).
In past winters, jetting out frozen water and sewer lines worked pretty well. But not this winter.
On Monday morning, Emily’s plumber started jetting through a clean-out in her driveway. He hadn’t made it 5 feet before disgusting raw sewage erupted through the driveway and backed up into the house again — this time even through the upstairs toilets!
Because of the hard deep freeze and long length of her driveway, Emily had to move her family out of the house and wait till the ice thawed to dig up and repair the broken sewer line.
Later that spring, Emily’s plumber ran a camera through to assess the damage done to the sewer line.
The video found one section had separated joints at both ends and a split along the top. After excavation it was discovered that section also had negative fall due to ice-related ground-shifting. This caused water to collect, transform into ice during the hard freeze, and build up massive amounts of pressure.
The Mechanics of Frozen Pipes
Freezing water can exert as much as 2,000lbs. of pressure inside a pipe — enough to tear any type of pipe apart.
While all pipes are susceptible to freezing, the type of material they are made of determines how they react to the enormous pressure of freezing liquids.
For instance, frozen galvanized pipe rarely splits length-wise. The expanding ice will grow until it encounters a Tee or 90 degree bend. Then it runs into other ice flowing toward it from the rest of the line. The pressure causes the back of the tee or bend to split and push out, creating a gap. Harder freezes cause larger gaps (usually around ¼").
When copper pipe freezes, it splits open at the point where the force of the ice is greatest, whether that’s along the pipe or at the fittings.
PVC and CPVC get brittle in cold weather and fracture where they freeze. This includes the pipe, the fitting, and the adapter. A hard freeze will split along the entire length from fitting to fitting.
PB pipe is probably not code compliant and should be replaced. But, if you still have it and can’t replace it right away, consider installing a low voltage, 120-degree or less, internal pipe heater to keep it from freezing.
PEX is not freeze-proof, but may thaw with no damage to the pipe and fittings. PEX is another good candidate for installing a low voltage, 120 degree or less, internal pipe heater to prevent freezing.
How Do You Keep Your Pipes From Freezing?
Be sure you have the pipes installed correctly. Besides inadequate fall, sloppy installation can cause other problems which lead to joint separation and damage.
Make sure to remove as much debris as possible before you install your plumbing system. If soil in your area is especially rocky, you may need to break the rocks up with a chain trencher to pulverize them. In some cases it may be best to remove the soil and replace it with sand.
However, with PVC, beware of soil that’s already sandy or "silty". This type of soil can cause shifting any time of year. While PVC is more flexible than other pipe, it can still break.
As our unfortunate homeowner, Emily, discovered, freezing and thawing can cause soil to shift and break even deeply buried plumbing systems.
If temperatures are consistently below freezing in your area and you can’t install deep enough to guarantee free flow, installing a "set-it-and-forget-it" internal pipe heater may be the easiest solution for long-term peace of mind.