3 Common Reasons Why Trench Drains Fail

A trench drain can be an expensive item to install. First, it requires an investment of time and energy to solve a drainage problem. Then there is the cost of the drain materials including the channel, top grating and shipping cost. The project will also require installation time and expense, as well as concrete and other supply costs. Whether you’re planning to use a contractor, or you decide to do it yourself, it all adds up. If it is a home project, there could be some personal frustration associated with the whole experience. The ultimate goal is for the drain to solve the problem.

If shortcuts are made, or the scope of the problem isn’t totally understood, this could lead to a trench drain failure. Often times, Trench Drain Systems™ is brought in to consult on the project after the owner’s failed drain is discovered. TDS™ has seen enough of these situations to lump the failures into three separate categories.

The Improper Installation

Polymer concrete has strength, but is brittle and will easily break in certain circumstances.

The most common mistake observed is due to a poor installation. There is a misconception that you don’t need to use concrete when installing a channel drain.  You should put this out of your mind. In most cases, you need to encase your trench drain in concrete.  A situation where concrete is not needed is drain installation in a paver patio where no vehicle traffic is expected. Using incorrect drainage materials and installation methods in a driveway  will likely result in a drainage system failure. The photo to the left shows a polymer concrete drain installed in a paver driveway.  Polymer concrete has a high compression strength, but is brittle and will easily break when dropped or put into dynamic force situations. The paver stones beside the driveway drainage system most likely settled with seasonal freezing and thawing causing the top edge of the trench drain to become exposed to the dynamic forces of the car wheels. This likely played a role in the channel walls collapsing at the base of the drain.

Concrete needs to closely adhere and encase the body of the channel. In the example below, the client poured concrete leaving a gap that was filled with grout. This method did not provide proper support from below or on the sides of the channel which caused the plastic body and grates to be crushed under vehicle weight. If the entire drain had been supported by concrete, the weight load of the car would have been transferred to the concrete leaving the channel and grate intact.

Driveway Drainage
Proper installation is just as important as having the right trench drain system to prevent damage.

Now, that leads to the question, “Can I use asphalt to install my drain?” Generally, the answer would be “No”. We have seen situations where the majority of the drain was encased in concrete, but the top surface adjoining the drain was tamped with asphalt compaction. This application is not something we like to promote. Encasing the entire drain in concrete is best as concrete does not expand as much as asphalt. The asphalt can be compacted next to the concrete. If there is an aversion to the contrast between the light grey concrete and the black asphalt, the concrete could be seal coated to make it blend in. If installation is handled differently, you may end up with a damaged drain like in the photo to the right.

Improper Drain Selection

Another improper drain selection situation is when you install a drain that will see a larger amount of water than it can handle. Again, the drain can be installed perfectly, but if the drain is overrun with a deluge of water, it is not serving its purpose. It is best to do a quick flow calculation prior to selecting your drain, just to double check that you have a drain that can handle the water flow anticipated.

Contractors and homeowners sometimes focus on appearance when installing trench drain systems. However, if the wrong drain is installed for the specific application, you have the potential to experience a system failure. One such example is when a plastic drain is installed in an area that involves fork truck traffic.

Some drains are meant for light duty and residential applications only. Plastic drains from the big box stores  such as Lowes, Home Depot and Menard’s are meant for use in a patio or driveway with little automobile traffic. The light duty construction of these channels will have a tendency to break under heavy loads or due to the freeze-thaw episodes seen in the winters up north and extreme heat in the south can cause warping.

For applications where a drain is going to see repeat traffic from automobiles, delivery trucks or fork trucks, a heavier duty drain is required. Drain bodies made from HPDE or polymer concrete with grating recesses that are supported by concrete (i.e. the grate is wider than the channel opening) are recommended. More preferable would be a channel body capped with a metal frame and heavy-duty grating.

Improper Grating Selection

Even an incorrect grating selection can lead to trench drain problems. The most common problems arise when the grating either has insufficient load rating, experiences extreme temperatures or insufficient chemical resistance.

Load rating problems are common. Inexpensive grates generally have a lower load class rating. A grate with a Class A load rating is intended for pedestrian applications. In some cases, they can still fail due to lawn and pool furniture legs which can crush through the grates. They are sometimes incorrectly used where automobile traffic is frequent thus leading to grating failure.  Unfortunately, we have seen instances where contractors or engineers chose a lower class grating to meet the budget of the project. Later, of course, it results in the owner having to replace the grates.

Stainless Steel Grates
Avoid damaging stainless steel grates with heavy traffic by getting reinforced grates.

This is the case with the example to the right where a winery installed stainless steel slotted grates with a Class A load rating. The application had required a grating with a much higher load rating. Stainless steel is already expensive, but the project owner settled on the cheaper stainless grates which couldn’t take the weight of pallet jacks and wine barrels. Needless to say, they later replaced the grates with reinforced stainless steel grates. This additional cost and downtime could have been avoided by making the right decision to use grates with the appropriate load rating for the initial installation.

Insufficient chemical resistance is also a common example of improper grating selection. It is important to consider the quality of the water or environment that the drain is going to handle. Sometimes it just slips out of our mind. Also, it may be tempting to ignore the possibility of the drain seeing an aggressive environment which would force the consideration of more expensive, chemical and temperature resistant grating options.

Corroding Grates
Animal waste and harsh chemicals shorten the life of galvanized steel grates.

For those who live near the coasts of Florida, California or Washington, the salt water atmosphere plays havoc on cast iron and galvanized steel. Eventually, trench covers corrode and need replacing. For coastal environments, it is wise to consider a grade 316 stainless steel, HPDE or fiberglass product when possible.

Likewise, in dog kennel applications, galvanized steel grating eventually corrodes from the animal urine and harsh cleaning chemicals. This leads to premature replacement of the grating. For non-profit organizations looking to cut costs, it is tempting to use a low-cost galvanized steel grate for the kennel application. It would be better in the long run to use the same recommended materials as coastal areas: stainless steel, perforated HPDE or fiberglass grating to avoid additional expenses later.

Takeaways

Most of the problems described in this post can be summed up as poor workmanship and poor selection. It is important to be sure the contractor installing your drain knows what they are doing. Is this their first trench drain installation?

Ask how many installations they have done. Also, don’t necessarily leave it to the contractor to find you a drain. Let them know you don’t want the local big-box store drains which are often plastic, incorrect for the application or aesthetically displeasing. This will prevent further investment of time, money and frustration to the project.

Contact the drain experts at Trench Drain Systems to help you with your drain selection. Take a look at our website trenchdrain.com or our online store trenchdrain.com/shop . Or give us a call at 610-638-1221, 8am – 5pm EST, Monday through Friday.