Why Do Pipes Burst?

Pipes Bursting are something many people that have had water damage in their home fear and they refer to any leaking pipe as a burst pipe. There is however, a difference between leaking pipes that has failed from corrosion or, erosion and a pipe that has burst.

Bursting by definition refers to something “breaking open, apart or, into pieces usually from impact or, from pressure within.” This definition excludes leaks that occur over time from corrosion of the material from water conditions or, erosion caused by high velocity flows, turbulence or, other problems where the pipe or its joints and fitting may develop leaks over time. Bursting is a failure that occurs suddenly usually without warning where good sound material fails.

The pipes will almost never see a high enough pressure to burst except for when pipes freeze. Water supply pressure in a home should be limited to no more than 80-psi and if the water supply is over 80-psi a pressure-reducing valve should be installed to regulate the pressure. Still even with high pressure and the possibility of a closed system with thermal expansion from the water heater the T&P valve on the water heater will release pressures above 150-psi which is well below any pressure that would cause a pipe to burst.

When pipes freeze the pressure within the pipes can rise from the expansion of the water that occurs when it freezes. This pressure can sometimes reach pressures as high as 40,000-psi from this expansion, which is high enough to burst any pipe material that cannot expand enough to absorb the expansion without bursting. Typically the high pressures are reached when 2 separate ice plugs form then freeze towards each other without giving the pressure caused by the expansion of the ice to an avenue for escape other than through the pipe material.

Metal pipes and CPVC pipes are the least resistant to freezing as the material offers almost no absorption of expansion without breaking or, splitting. Piping done with PEX tubing is probably one of the most resistant to bursting from freezing as it can in most cases expand enough to absorb the expansion from ice forming without bursting. There are several exceptions to PEX being damaged by freezing most notably when PEX-AL-PEX is used for tubing or, when the fittings are between 2 to 7 inches apart.

The best way to ensure that pipes do not burst from freezing is to make sure that you keep your home adequately heated in the winter and that the pipes are in a heated area without exposure to cold drafts which can cause freezing.