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Causes of smelly drains: Part 2 - Defective Plumbing

So far in our Grate Tips blog series on the causes of smelly drains, we’ve looked at bacterial build up and blocked pipes. In part three we’ll be moving on to the other main cause of drain odors, defective plumbing.

In some cases smelly drains are caused by the loss of the seal created by the plumbing trap. Basically this is where the water level in the trap drops below the u-bend in the pipe, allowing for the free passage of gasses back and forth. The following sections describe different causes in more detail.

Defective Plumbing

It should come as no surprise that if your plumbing is defective then there can be some nasty side-effects such as bad smells. So, what kinds of faulty or defective plumbing can cause bad smells?

Venting

A well-constructed drainage system needs to not only allow for waste water to flow, but also air and gas. Why air and gas as well? When you were small, did you ever have fun by get a drinking straw, placing it in a glass of milk or soda, popping your finger over the other end of the straw and lifting it out? Your drink stayed in the straw because by placing your finger over the end, you effectively created an area of low air pressure. The air pressure under the straw is now higher than the top and the liquid stays put. Remove your finger and your drink flows freely out the bottom. A simple visual can be found here

The plumbing in your house or business works on a very similar principle and the technical term used by plumbers is venting. If no venting has been allowed for then the waste water will have trouble flowing through the pipe, or flow slowly. If the plumbing has too much venting allowed for then not only does the waste water flow freely, but it allows for smelly gases to come back.

Cracked Pipes

If you have cracked pipes, especially in the area around the base of the trap, the water seal can drain away, or lower. The lowering of the water level allows sewer gases to flow, or vent back into the room. Cracked pipes are usually more of a problem in older buildings as materials used, especially clay, can degrade over time. Good quality, modern PVC pipes, if installed properly and if free of intrusion from tree roots, should last for many years.

Poor Workmanship

If an unqualified or unscrupulous plumber has been employed to install the plumbing, it is possible that they either haven’t installed a trap, have installed it incorrectly or haven’t sealed the joins properly. All three of these scenarios can cause gas to vent back through.

Low water levels explained

Low water levels can enable the free-flow of gases from the sewer in to your living area. The diagram above gives some examples of how this can occur.

Low water levels can enable the free-flow of gases from the sewer in to your living area. The diagram above gives some examples of how this can occur.

What can you do to solve drain odours?

Depending on the exact situation, fixing a venting problem can be quite problematic. If a drain has been incorrectly vented then the only permanent solution is to have a qualified plumber manually re-vent the system. Likewise if you have a cracked or poorly constructed line it is best to have it professionally repaired or replaced.

If your budget is constrained, if you are renting and your landlord is reluctant to address the issue, or if you need to defer the repair work, installing a Grate Seal is a cheap and effective way to get rid of drain odours. Simply remove the drain cover and insert the Grate Seal and you will notice almost immediately the smell has gone. The Grate Seal is a durable, one-way rubber valve that lets wastewater through while preventing smelly gases and insects from coming back. The Australian made Grate Seal comes in a number of sizes and is suitable not just for most domestic shower and floor drains, but also in commercial setting. 

You can view a short video demonstrating just how quick and easy it is to install a Grate Seal here.

Smelly drains can be especially problematic when there is limited space available

Smelly drains can be especially problematic when there is limited space available

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