A good drainage system is at the core of every good shower, ensuring a safe, clean and hassle-free experience. But which drainage solution you choose will depend on a variety of factors, including flow rate, project cost, flooring and layout. In this guide, we examine these key considerations and explore the options available for a variety of construction projects.

A drain’s main function is to guide the flow of water towards a point of egress. Failure to do so can lead to water pooling, which creates slipping hazards and damaging build ups of moisture.

Continuous damp leads increased mould and can increase the inside humidity levels of the house, increasing the health hazard of mites and bacteria. In the long term, pooling water can lead to rot, rust and eventually, structural failure.

Needless to say, high quality drainage solutions that do not require constant surveillance or upkeep are essential to creating a high-end, satisfying experience for the end user.

Key Considerations When Choosing Drains

When designing showers, the primary goal is to contain the space with direct water exposure while maintaining ease of access. Many traditional shower drainage solutions rely on curbs or shower trays to separate wet from dry areas. However, this is not always suitable, as it poses a tripping hazard, making it harder for less mobile or elderly occupants to man. As a result many architects prefer linear drains, which eliminate traditional barriers and allow for easy entry into a shower without compromising on high capacity water removal rates.

Project scope

Needs will vary depending on the size and scope of your project. Whether you're building luxury homes with a variety of bathing options, or refurbishing hotel bathrooms, you need to be aware of cost, availability of parts and installation time.

The easiest way to cover the first two considerations is to review the options available and order the most cost effective drain components. When choosing a supplier, make sure that the goods are of the highest quality and fully certified.

While one bespoke option might be ideal for your design, cost is always a limiting factor. Keep your choice of drain realistic to remain in budget. But where possible, try to ensure quality parts. The cost of one bad component multiplied by a an entire new build project can easy spiral out of control.

When it comes to installation time, you need to ensure that you have a qualified fitter who understands how the drain is put together so you can ensure a reliable and timely fit. Installing a  linear drain also allows shower floors to slope in only one direction. This makes screeding and tile fitting easier and faster, and giving builders more plumbing and tanking arrangement options.

Large format stone or tiles may furthermore be used with linear drains without needing cuts to create the correct falls. This saves costs and time during the setting out and tiling stages, and creates a more seamless aesthetic.

One of the other key considerations of project scope is the user. The needs of the end user should always be taken into account during design, of course, but some overlook the impact drainage can have on the user experience.

If you are fitting wetrooms in luxury apartments for infrequent users, you will need a drain that prevents odors from spreading. Drains that go unused for long period of time can be left with stagnating water that can cause bad odors. A water-less drain trap is a perfect solution to this need.

Alternatively, if you're installing bathrooms for new builds with lifetime housing design principles in mind, you need a drain that is capable of managing a variety of flow rates over many years.

Shower layout

The dimensions and layout of the shower enclosure will likely determine the length of the drain and where it will be placed. If the project is new construction, you’ll have some freedom with the layout. A remodel, on the other hand, could possibly have some existing site-specific conditions that might place limitations on what’s achievable.

In the case of a refurbishment, consider any existing pipework that might obstruct the placement of a drain. Explore the possibility of fitting one larger pipe to accommodate new drainage into existing systems rather than fitting another pipe into the space. This can save space in the floor and reduce the cost of materials.

The good news is that no matter what the layout is, many linear drains can be cut-to-size and customized to your specific needs. This allows for a perfect wall-to-wall installation, and the most efficient evacuation of water. As a general rule-of-thumb, linear drains are located at either the back or side wall of where the fixtures are installed, or along the threshold or entrance.

However, when you are considering your drainage options, discuss with your supplier any bespoke needs you might have. They may be able to create a unique solution that is ideal for your specific requirement. 

Will the shower have a shower tray or curb?

There may be specific reasons why a client requests a barrier-free shower over one with a curb. You may be building to lifetime home specifications, or have a client with a mobility issue. If your spec requires the user to have the freedom and ease to access their shower without any limitations, you need to consider that when choosing your drainage requirements.

When trying to install and shower without a shower tray, the primary issue is floor height. Linear drains with a shallow channel or modern tanking techniques can help decrease overall floor height to achieve an easy, barrier-free installation. Furthermore, certain decorative styles or ultra-narrow widths are not advisable for barrier-free showers when placed along the threshold.

Which tanking technique will be used?

Tanking (waterproofing) a bathroom or wetroom require different channel fabrications, so you need to consider which technique you are going to use when choosing your bathroom drains.

Traditional waterproofing techniques are the most popular options in the United States. They utilize a clamping flange to connect to the waste line. A PVC  or rubber shower pan liner is the most common. However, certain states and regions have their own techniques. In California, for example, you will often find that hot mopping is more common, while in the Northeast, lead or copper shower pans are more heavily favored. Linear drains that work with traditional waterproofing need to be flexible in order to meet specific regional regulations.

If installation efficiency is one of your key considerations, it may pay to explore more innovative tanking options. Liquid membranes and sheet membranes have been proven to make the installation process faster and more efficient. An extra benefit of these modern techniques is that they allow tile setters to tile directly on top of the surface, as this makes installation faster and easier.

While some fitters choose one option or the other, we find that a "belt and braces approach," utilizing both sheet membrane and a liquid membrane provides the most reliable waterproofing.

Choosing these tanking options requires a linear drain channel with a flanged edge. This provides a surface for the membrane to bond to the channel. The waterproofing then continues over the shower floor and up the walls. This will provide a seamless waterproof area, which is essential for shower areas and wetrooms.

Fixture flowrate

Flow rates of shower fixtures need to be calculated early in the planning phase. The limits of your fixtures will ultimately be determined by how much water your drains can handle. The linear drain must be able to handle the combined flow rate of the fixtures installed in the shower.

For example, a shower may include a rain head, hand-held, and a traditional shower head, each with a flow rate of 2.5 gallons per minute. Standard linear drains can handle up to 6 gallons of water per minute when connected to a 2-inch waste line. If your requirements extend to additional sprays and similar fixtures, you will need to adjust your drain accordingly.

Thanks to its larger drainage area, a linear drain can handle higher flow rates more effectively than a traditional square drain. Ideally, you want as much of the water you use to flow into the drain and not pool. If needed, flow rates can be further increased by the addition of up to three traps positioned along the length of the linear drainage area, as you can see from the table below.

Flow Rate/Traps Calculation

It’s been said that the best drainage systems are those that go unnoticed, but for industry experts, the opposite is often true. Choosing the right component for the right project is what makes the difference between project success and delays, complications and unnecessary costs.