Blocked Commercial Drains: The Common Causes

Blocked Commercial Drains: The Common Causes

Commercial drains can become blocked for numerous reasons, and blocked drains can bring many issues and challenges. These can range from simple unpleasant odours, to environmental incidents and the propagation of mould and mildew, and even structural damage to premises. In this article, we examine the primary reasons drains can become blocked, as well as the most common methods deployed to clean them. Ongoing drain maintenance significantly reduces the risk of block drains – to learn more about this refer to our drain maintenance guide.

Common causes of blocked drains


The most obvious cause of blocked drains is debris. Whether this debris is foliage, twigs or other natural materials that have been naturally displaced, or foreign materials introduced by human activity, like soaps, toilet tissue and sanitary towels, and waste food; they all have the capacity to obstruct the flow of water between drains and the pipes that run underneath. This isn’t usually an immediate problem, as water can often still pass through minor obstructions. A drain that has been left to accumulate debris over a period of time will eventually become completely blocked.

Grease & Fat

Despite press about fatbergs plaguing municipal sewer systems – most notably the recent London fatberg that the council had to invest considerable time and expense removing – an excessive amount of fat and grease still make it into drains and pipes. This fat and grease coats the walls of pipes with a sticky coating that clings to other debris in the water flow, which gradually builds up into an impenetrable mass and causes a blockage.

Heavy rainfall

Higher than average rainfall not only causes issues with flooding due to excess water run-off, the resultant collection of leaves, mud, dirt and other matter also finds its way into drainage systems and can cause blockages. The majority of drains (storm drains aside) are not built to handle excessive amounts of debris, which makes blocked drains after heavy storms commonplace. Blocked drains outside properties are likely to cause localised flooding, which can cause damage to properties if left for a prolonged period of time.

Water flow problems

Drainage relies on gravity to transport water from one place to another. Water won’t flow uphill, so pipe installations need to be correctly installed and feature adequate falls to ensure continued water flow and that particles of debris don’t start to build up. Early warning signs of bad water flow include slow draining water, gurgling sounds from flushed toilets, and bad smells emanating from sinks and drains.

Broken pipes

When pipes become cracked and break, water is unable to flow freely, which may cause the pipe to collapse and the drain to become blocked. The causes of broken pipes can be through simple old age, or they could have been incorrectly installed; alternatively, pipes can be damaged by tree roots, which can cause a lot of damage before the problem is identified. Underground pipe repairs can be expensive and hugely disruptive, depending on how easy or difficult it is to access the area that’s broken.

Drain cleaning methods

drain cleaning methods

Drain snaking

The simplest method of clearing a blocked drain, and the first a conventional plumber may deploy, is called drain snaking. A drain snake (a.k.a. a drain auger) is a length of cable with an ‘auger head’ that’s sized appropriately for the pipe to be unblocked, and can locate and remove blockages fairly simply. While drain snakes are able to reach fairly deep into sewage and water pipes, sometimes blockages are too severe to be tackled in this manner, meaning other more advanced cleaning methods will need to be deployed.

Drain jetting

The preferred method for removing blockages from drains and pipes is called drain jetting (a.k.a. hydro-jetting). This process uses a stream of highly pressurised water, much like a pressure washer, along with a special head that directs the spray and scours the inside of commercial drains as it moves along the pipe, clearing even stubborn blockages in the majority of cases. This method is often preferred as it is proven to be the most effective at clearing blockages almost instantly, causing minimal disruption and without any backflow; and it is especially preferred for clearing blocked drains associated with the food, beverage and hospitality industries, where there’s likely to be a high incidence of troublesome oil, grease and fats clogging the drains, as well as fibrous and food materials.

It’s a good rule of thumb to have your drains professionally cleaned at least every three years, preferably more frequently. Drain cleaning should also be undertaken following any instances of extreme weather. Enva are commercial drain maintenance experts, and offer a range of drain services from drain testing, to drain cleaning and jetting, helping you keep your business running smoothly.