3 Common Corrugated Metal Pipe Problems and How to Fix Them

Corrugated metal pipes (CMPs) are some of the most commonly used materials for underground stormwater infrastructure. They go largely unnoticed, but are necessary to support the daily functions of our lives by properly moving water to avoid issues like water ponding, standing water on roadways, and localized flooding.

For more information, please visit YiTong.

CMPs are used for various underground infrastructure projects such as culverts, stormwater detention/retention systems, storm sewers, small bridge replacements, aeration pipes, material conduits, and more. 

CMPs can require frequent maintenance and repairs if they aren’t given adequate protection through the use of things like structural polymeric linings. Keep reading to learn about CMPs, 3 common issues they face, and how to fix them!

What is a Corrugated Metal Pipe?

A corrugated metal pipe (CMP) is a pipe—used for culverts and other underground infrastructure—that has a distinct set of parallel grooves and ridges. 

As mentioned, they’re most commonly used for drainage culverts, storm sewers, material conduits, and other underground stormwater conveyance infrastructure pieces. 

CMPs are commonly manufactured out of aluminum and steel, with different metallic coatings and alloys designed for different applications. 

Corrugated Metal Pipe Materials: 

Aluminum Alloy 

Aluminum alloy CMPs are designed to resist the effects of corrosion and abrasion underground. The surface of the core is coated with a higher-grade aluminum alloy.

Aluminized Steel 

Aluminized steel CMPs are manufactured by hot-dipping steel CMPs in commercially pure aluminum. These pipes can be effective at combating corrosion, in particular for culverts and drainage systems that involve acidic water. 

Galvanized Steel 

Galvanized steel pipes are manufactured using a process called—you guessed it—galvanizing. Galvanizing involves applying a zinc coating to the pipe, thus protecting the base layer of steel from corrosion. Typically less effective than aluminized steel, the zinc helps protect from corrosion by acting as a barrier between water and the steel, reducing the effects of rusting and deterioration for the short term. 

Asphalt-Coated Galvanized Steel

Asphalt-coated galvanized steel pipes are similar to galvanized steel pipes, but they’re coated on the interior and exterior with asphalt to delay corrosion and deterioration for a longer period. The asphalt, in combination with the zinc coating, provides additional abrasion resistance and helps to prevent water, debris, and abrasive run-off from reaching the base layer of steel.

Polymer-Coated Steel

Polymeric coatings and structural linings are emerging as great options in the industry to help CMPs stay sealed and strong. Polymeric coatings protect against abrasion from acids, salts, alkalis, and other materials that threaten CMPS in culverts and sewers. 

Common Corrugated Metal Pipe Problems: 

#1. Open Joints 

Corrugated metal pipe joints are the areas/pieces that connect different adjacent sections of pipe. These areas can be a source of problems if they are opened due to misalignment. In these scenarios, backfill material can erode into the pipe, causing structural deterioration and eventually failure if left untreated.

To fix open joints, a process called joint sealing is carried out. It’s as simple as it sounds—the joint is sealed off to prevent unwanted material from entering. Polymeric linings are great for joint sealing, providing structural rigidity against soil intrusion and hydrostatic pressure

#2. Voids 

Voids are unwanted gaps/spaces between the CMP and the soil. They’re addressed by using polyurethane grouting to fill the void and using polymeric linings to seal/strengthen the CMP.  

#3. Deteriorated Inverts

The invert of a corrugated metal pipe is the lowest point within the pipe that water flows across.

Since this is where the water makes the most contact with the pipe, it’s especially susceptible to abrasion during peak stormwater events and corrosion over time if left unprotected. Deteriorated CMP inverts are likely the most common and frustrating corrugated metal pipe problems that underground infrastructure professionals face. If the pipe doesn’t have a long-lasting, abrasion-resistant corrosive protective agent like a polymeric lining, it can rust through. 

Featured content:
Questions You Should Know about Vertical shaft impact crusher

The company is the world’s best Corrugated Steel Culvert Pipe supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.

Once the invert rusts through, other serious problems can occur like voids or even total structural failure.

How Are These Problems Fixed? 

While there may be numerous approaches available in the market, many professionals are starting to see the advantages of trenchless pipe repair. 

Trenchless pipe repair means fixing underground pipes from the inside. These projects can be carried out to completion within a few working days, far shorter than digging from the surface and ripping up roadways to get to the pipes.

Polymeric linings—as mentioned in the Corrugated Metal Pipe problems section before—are a great trenchless solution for CMP repair and rehabilitation.

One of the best products any trenchless pipe repair professional can use is SprayWall®, a polymeric lining that not only seals CMPs but strengthens them as well. 

In fact, SprayWall® is scientifically proven to increase the load-carrying capacity of corrugated metal pipes by up to 800%.  

Last year, SprayWall® was chosen by the University of Texas at Arlington for a study aimed at creating testing and application standards for spray applied pipe rehabilitation liners in multiple Department of Transportation markets.

A key finding from the report was the fact that SprayWall® was strong enough to be considered structurally capable to perform as a new pipe inside of the host pipe. 

SprayWall® lasts over 50 years and cures completely within 72 hours of application. It begins to gel within 8 seconds and is tack-free after two minutes.

This means trenchless repair crews who use SprayWall® will have completed an entire project in the time a crew would need to dig up and bury what they’re working on. 

Overall, SprayWall® helps make CMP repair faster and more effective, with results that last for decades.

Conclusion

Underground infrastructure—supported by things like CMPs—is vital to our society, so it’s important that we keep it protected. 

Trenchless repair methods for corrugated metal pipes are proving to be the superior solutions when applicable, as they save communities time and money through long-lasting solutions and minimal disruptions. Whether the issue is corrosion leading to maintenance issues, or deteriorating inverts posing a threat for structural failure, trenchless solutions like SprayWall® can solve the problem. 

SprayWall® is minimally invasive and saves engineers, contractors, and communities their time and money. 

Have questions about SprayWall® or want to learn more about applying to become a Sprayroq™ Certified Partner? 

I need to put in a 20' culvert to extend a road to an RV pad I am building. I need to be able to drive both a 14,000 # motorhome and my # tractor over the culvert, not at the same time.

I have seen both metal and plastic used, the costs are close in my area.

Which is the preferred type & why?

Second question:

How do I tell what size to use? The county says 12" minimum everywhere, but for the difference in cost I would rather do it right (maybe some overkill) the first time than replace it next year if it is too small.

From the topo map, it looks like the water from 10-20 acres of 15%+ slope drains through this spot. The culvert will have about a 10% slope.

I am sort of leaning to 24" diameter, which only costs twice as much as 12".

The culvert is going into a natural gully and not a ditch. I looks to me like there will be over 3' of fill over the culvert at one end, and over 5' at the other.

Third Question:

Do I need to fill around the culvert with gravel or can I just use the dirt I excavated for the RV pad?

Forth Question:

Should I have some kind of grate to prevent debris from entering the culvert? CurlyDave,

I like plastic since it won't rust.

You need at least 12" of material over the culvert to get the maximum strength. Mine is covered maybe 6"-8" but it handled 55-60,000 pound dump trucks just fine.

I used ABC to cover the culvert since that is what I was using to build the driveway. Most people would use whatever soil they had available.

I think mine is 18" in diameter. I got mine for free so I used it. I don't get much water in mine since the culvert is only about 50 feet from the top of a hill. I would want 18" or larger culvert since I think it would be harder to stop up in the first place and if it did get clogged it should be easier to clean out.

10-20 acres can generate alot of water. Since it sounds like you have a deep ditch a bigger culvert would be better. Bigger than you need is better than not enough culvert. You might want to contact you county extension office and see if they can give you some guidence to size the culvert. 1 inch of rain on 10 acres is alot of water....

Later,
Dan I'm a long way from being an expert here but with the weight on the MH (possible 8-9k# on the rear axle) and not knowing anything about the "dirt" I'd be a little concerned whether the plastic culvert could handle the stress. Does the galvinized steel have spiral flutes? This adds to the strength considerably. The trade off is that somewhere down the road the galv/steel may rust out as zinc is water soluable.

As for the grate, on a 24" culvert one might not be needed depending upon what gets washed down the gully. With a grate you could find yourself having to clean at least once a yr. I'd do some asking around from others in the area that have done it both ways and see what their feeling are.

Up the road a piece at MP #272. Plastic is better than metal for several reasons. First, it will never rust out on you. EVER. Second, get the type with the smooth inner wall. It stays cleaner and doesn't hold silt and debri. As for strenght, both rely on preasure from the fill material being equal on all sides. You need a certain amount of fill on top based on the size of the pipe you install to reach maximum strength. For an RV, you will need this. For a car or light tractor, the amount on top isn't as important.

Since you want to create a crossing over a ravine, go as big as you can. That ravine was created by allot of water. The size of it shoud tell you the amount of flow you have to deal with. 24 inches is a huge pipe and should be able to handle most situations, but there is a reason they make bigger pipes and/or install two side by side.

Putting grates in front will cause more problems than it would solve. Small leaves will wash right through it, but with a grate in front, they will create a dam. It's very rare to see one along highways or anyplace that they are put in profesionally, so I'm thinking you don't need one. I don't have any on mine and so far haven't had any issues.

Backfill is usually with clean soil, but sometimes sand is used instead. Rock isn't any good because of the voids and dificulty in getting it all compacted. At the entrance to the pipe you will need to put something down to stop erosion. I've used sacks of cement for this with good results. Of course, it's not as attractove as rock. If you use rock, be sure it's big enough not to wash away or let the water through it. Small rock is useless during a heavy storm.

And always plan for the very worse that can happen.

Eddie I am with Eddie. Go as big as you can. 10-20 acres draining thru a 6' or 7' deep ravine can be a lot of water. And you want it to go thru the culvert, not over the top.
And as Eddie said, don't use loose rock or gravel for fill. You don't want the water seeping around the sides of the culvert.
I have a 24" culvert in the ditch coming in off the road. I had to have some fill dirt hauled in but it was similar to what I have on my land. Once it is filled and packed, the circular nature of the pipe is very strong. Weight on top tends to push the dirt down around the sides of the pipe. That applies extra pressure to the sides adding support to the top. Due to the depth of my ditch, I have only about 1' fill on top of mine. But when I built my metal building, they brought in all materials on a flat bed semi. No problem at all driving it over the culvert. Oh. mine is metal.