Controlled Emission Toilets: Key features and implementation

March 24 2021
Rail wash

Controlled Emission Toilets (CETs), also known as toilet retention tanks, are now the rail industry standard - expected by operators and train users alike. Simply put, CETs store waste in a large, secure tank in the train’s body instead of depositing the sewage directly onto the tracks. Every night when the train reaches the depot, the waste can then be easily pumped out of the tank and disposed of safely.

CETs are more hygienic for travellers - with the sealed tanks able to prevent unpleasant smells from escaping - and much kinder to the environment and the people working on railway lines. Retention tanks are now commonplace enough for operators still using older-style toilets to receive negative media coverage for doing so.

Controlled Emission Toilets are therefore a must for all newly-produced trains, and increasingly important for older rolling stock to be retro-fitted with. Read on to learn more about the pressing need for CETs and their implementation challenges.

Why all trains need CETs

In the UK, Network Rail is aiming for all trains to have CETs fitted by 2023 - meaning the race is on for operators with older rolling stock - which still makes up a significant proportion of trains. But even in regions where such targets don’t exist, pressure from governments, the public and the railway unions mean this is a problem that can’t be avoided for long.


CETs are available in a range of different configurations to suit the infrastructure they will have to work within. For instance:

  • Emptying systems are available in manual or automatic options.

  • Most toilet retention tanks are cleared from fixed trackside extraction stations, but mobile extraction units are an alternative option for depots with limited space.

  • Underfloor systems are another option for where trackside space is at a premium. Each module connects to a main vacuum waste water line to dispose of sewage safely and rinse tanks with clean water.

  • Remote diagnostics can be installed to monitor tank levels and identify any potential problems before they become serious.

How difficult is it to install toilet retention tanks?

All modern train fleets are built to accommodate Controlled Emission Toilets, with the main requirement being adequate space and access to the train’s plumbing system. It is when it comes to retro-fitting older trains that more problems can occur.

Unfortunately, operators know that replacing an old toilet with a modern CET requires more than just bolting a tank on. Space on the underframe needs to be created to accommodate the tanks - and as there often isn’t the room for this to be directly under the toilets themselves, pipes will likely need to be re-routed. Installing vacuum systems to enable more powerful flushing and save water adds another layer of complexity.

Retro-fitting an entire fleet can be a major operation, which is why operators are often reluctant to sanction upgrades. There are very live concerns over rolling stock being out of action for extended periods - putting more pressure on already squeezed capacity. However, with new, modern fleets often taking years to arrive, retro-fitting is nonetheless essential in the medium term.

What operators and manufacturers of new trains both need is access to the right expertise and a range of CET options. Not only will this ensure the best systems for the job, it will also mean as quick a turnaround as possible and prevention of costly delays. At Wilcomatic, we know the rail industry inside out. Our industry-leading designers and engineers are on hand to plan, build and install the best solution for your fleet’s needs.

Alongside our main role as a supplier of cutting-edge rail wash systems, we also specialise in other train technology including CETs, lubrication systems, T-system satellites and pump stations. To find out how Wilcomatic can help your fleet, get in touch today!

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