The most durable sewer pipe materials are PVC, HDPE, and cast iron. PVC and HDPE resist corrosion and chemical damage and last 50–100 years. Cast iron is extremely strong and often lasts 75 years or more. Clay and concrete also last 50–100 years but are more prone to cracking.
For sewer lines, Schedule 40 PVC is a common and durable choice for residential projects, while SDR35 is a cost-effective alternative suitable for residential drainage where flexibility is key. DWV (Drain, Waste, and Vent) pipe is another option specifically designed for non-pressurized drain lines.
Dig-up test results in the U.S. and around the world indicate that PVC pipe can be expected to provide reliable service in excess of 100 years. The average water main is failing at 4 7 years. Corrosion is the major cause.
PEX is significantly more vulnerable to UV than PVC. While brief exposure to sunlight during installation is acceptable, it cannot be used in above-ground or outdoor applications. PEX fixtures, on the other hand, are solely limited to indoor or underground outdoor use.
Mistakes During Underground Installation
One of the most common mistakes is not following the required burial depth. According to the NEC (National Electrical Code), the minimum burial depth for rigid nonmetallic conduit (PVC) in most residential applications is 18 inches.
Best PVC Pipe Types for Underground Use
For most underground applications, Schedule 40 and Schedule 80 PVC pipes are commonly used due to their strength and resistance to corrosion. Schedule 40 PVC: A cost-effective choice for low-pressure applications, such as residential water lines, irrigation, and drainage systems.
Leaks and Fittings Issues
PEX plumbing uses fittings and connectors that are typically made of plastic or metal. Over time, these fittings can loosen, leading to leaks. Problems can arise with crimp rings, as improper use of a crimping tool can weaken the joints.
Myth: PEX tubing has a short life span. Fact: The life span of PEX tubing can vary based on frequency of use, water quality and water temperature and has an average life expectancy of 40-50 years.
Estimate the length, width and depth of the trench based on what you need to install underground. For instance, a 4-inch pipe for a French drain should be installed in a trench 6-12 inches wide and 18-24 inches deep. In that case, you will need a 24-inch trencher.
You can use both PVC and PEX pipes for an underground water line. Both are able to be buried and can withstand high pressure. They are also resistant to rusting and corrosion. You can also use copper plumbing pipes for underground plumbing, as they are resistant to rusting and leakage.
The most durable sewer pipe materials are PVC, HDPE, and cast iron. PVC and HDPE resist corrosion and chemical damage and last 50–100 years. Cast iron is extremely strong and often lasts 75 years or more. Clay and concrete also last 50–100 years but are more prone to cracking.
Pipe for conveying liquids susceptible to freezing should be buried no less than 12" below the maximum frost level. Permanent lines subject to heavy traffic should have a minimum cover of 24". For light traffic, 12" to 18" is normally sufficient for small diameter pipe (typically < 3" diameter).
The 135 rule means horizontal drain pipes cannot connect using a fitting that creates more than a 135-degree change in direction. In plain terms, you cannot use a standard short-turn 90-degree elbow between two horizontal drain lines. Plumbers use two 45-degree elbows, a long-sweep 90, or a wye-and-eighth-bend instead.
The primary difference is the wall thickness. Schedule 80 PVC is designed with a thicker wall, making it stronger and capable of handling much higher water pressures than Schedule 40 PVC.
The most common sewer pipe types include clay, cast iron, Orangeburg, PVC, and ABS. Each material has different strengths, different weaknesses, and different long-term repair considerations.
It was my understanding that a typical kitchen drain used 1-1/2 inch and a typical bathroom sink used 1-1/4 inch. And at Home Depot they had the kitchen stuff together, and everything was 1-1/2 inch. And they had the bathroom stuff together, and everything was 1-1/4 inch.
Ever heard of the 5-4-3-2-1 trenching rule? ✔ 5 feet: Trenches 5' deep must have a protective system. ✔ 4 feet: Trenches over 4' need a ladder for exit and egress. ✔ 3 feet: Ladders should extend at least 3' above the excavation for easy access. ✔ 2 feet: Keep excavated materials 2' away from the edge of the trench.
A layer of gravel (see below for size recommendations) should be placed in the trench to a minimum depth of 1 inch. It may be deeper, as necessary, to ensure minimal slope requirements. All drainage pipes should be placed on the gravel bed in the trench.
If the slope is too steep, water can flow too quickly, leaving solids behind. If it's too shallow, water can move too slowly, leading to sediment buildup. The ideal slope is ¼ inch per foot of pipe, ranging no more than 3 inches.
Rodents, particularly rats and mice, are known to chew through PEX plumbing. Because the material is soft and easy to gnaw, even a small rodent problem can lead to leaks, water damage, and costly repairs hidden inside walls or under floors.
PMRs for malignancies of the stomach, kidney, brain, and lymphopoietic system were also elevated, especially among plumbers. Chronic rheumatic heart disease, emphysema, liver cirrhosis, and all external causes of death were the major non-cancer causes with significantly elevated PMRs.
Summary. Copper water tubing has an outstanding history of corrosion resistance in most underground environments. Copper does not naturally corrode in most clays, chalks, loams, sands, and gravels. Certain aggressive soil conditions, however, can cause it to corrode.
Effects on Metal and PVC Pipes
While harmless for most metal and PVC pipes, prolonged exposure to the acidic nature of vinegar might corrode certain metals, like copper. PVC pipes, on the other hand, can withstand these substances without damage.
Despite these benefits, some insurance companies have raised concerns about PEX plumbing, particularly regarding older installations: Historical issues: There were class action lawsuits against PEX manufacturers due to premature failures at connection points, resulting in leaks and flooding in some cases.
About SharkBite PEX Pipe
You can find our USA-made PEX-a and PEX-b pipe at wholesalers, on Amazon, at many home improvement retailers or at your local hardware store. SharkBite PEX is: Approved for use in potable water installations.