5 Common Drainage Design Mistakes to Avoid

Drainage functionality needs to be considered when constructing a new building or space. If this doesn’t happen, drainage design mistakes can occur and cause a multitude of issues. The best way to minimize drainage design mistakes is by learning how to spot the most common issues – before they happen.

Drainage Design Mistakes drainage design mistakes Drainage Design Mistakes "This is where XXX council cambered the paving but wouldn’t go the extra cost of a drain!!!"

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"Plaza, do you even drain?"

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"Great job on paving, but why oh why after many years do we still have a drain problem."

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Common Drainage Design Mistakes

Drainage Design Mistake #1: Improper Sloping

The slope leading towards the drain is what gives the fluid it's movement. Improperly sloped floors will lead to pooling, which can further cause problems. Pooling can damage the concrete and compromise building structures. The location of the drain should dictate where the floors should be sloped. All flooring needs to be sloped towards the drain, in a smooth grading of 1/8 inch per foot. To ensure that pooling from poor sloping won't occur, a grading of 1/4 inch per foot would be recommended.

Drainage Design Mistake #2: Not Enough Drains

Building codes require facilities to have adequate waste water removal systems. Anywhere in the facility that may be subjected to water needs to have some form of drain that is capable of handling the fluid. Car washes need drains that can carry large amounts of water, or more drains. In outdoor applications, for everywhere it rains, there should be a drain. Drainage needs to be present in public spaces, parking lots, and roadways. The amount of drainage should always reflect the estimated amount of water, and then some to accommodate heavy rains, big spills, or larger productions.


Drainage Design Mistake #3: Safety

The safety of the public, staff and others should be top of mind when constructing drainage. Some drainage systems are known for breaking down and causing dangerous situations. Drains need to be maintained and replaced if necessary to eliminate the safety risks. In one case, a woman tripped and fell in a drainage system that wasn't properly cared for. She was able to successfully sue the company responsible and win a $456,000 payout for her injuries.

Read more: Pub car park fall: woman wins $456,000 payout

Drainage Design Mistake #4: Drain Maintenance

Drain maintenance can be a deciding factor in how functional the drain will be. If the drainage system is not maintained, debris can quickly plug the drain and lead to pooling. When selecting a drain, really consider who will be maintaining the drain. If it is installed in a public space, how often will the workers clean out the debris, is there a filter? When the drain is plugged, how easy is it for someone to clear? Drainage systems that have built in filters will help with drain maintenance. Even better, find a drain that has automated flushing to eliminate the need for frequent drain cleaning


Drainage Design Mistake #5: Environmentally Friendly Drains"

When selecting an environmentally friendly drain, consider the materials and product life cycle. Materials such as stainless steel will last much longer than drains constructed from PVC. A slotted linear drain will also last longer than drains that require grating, because the grating will break down.

Download Drainage Design Guide for Multiple Applications


How to Avoid Drainage Design Mistakes

The owner, architect, engineer and general contractors must work together and solve the problems. Communication among all these parties is essential. If you are not sure which drain to use in a specific application, talk to engineers and consultants.

Talk to a Drainage Consultant

Do it right at the first time

If the slope rate is not appropriate to drain away the water, or there’s not enough drainage, you may need to cut out concrete, rip up the entire floor and install with appropriate plumbing. That does not worth it and will cause a lot of other problems. Cheaper options are not necessarily better if you consider the long term maintenance. Doing it right at the first time will save your client time and money.

Look for variables and possibilities

Trench drain with covers might not be the best option for your design, as grates will rust and deteriorate and cause public safety issues. There are many alternatives that you may consider using. Get rid of grates and unnecessary drainage troubles.



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