Why Water Authorities Turn to T-T for Evidence-Led Wastewater Design

At T-T, we are regularly asked to review and support wastewater designs where long-term operational performance is critical. That trust is built on one thing: experience grounded in evidence.

On a recent project, we challenged a request from an established UK NAV to increase the diameter of a rising main. The reasoning presented followed familiar industry assumptions that larger pipes are more reliable, reduce blockage risk, and better suit commonly available pump configurations.

Our review showed otherwise.

Because we don’t rely on convention alone. We validate, emulate, and assess designs against real operational data, the same conditions assets will face once they are built, commissioned, and maintained.

Understanding the Risks That Matter in Operation

One of the reasons water authorities and contractors work with us is our focus on what happens both before and after system adoption.

Far too often, the focus is upon the Water Authorities' wants and needs, and rightly so.  However, the developers' journey leading to adoption can be fraught with operational cost and risk; a strong focus on both time periods is important.

Septicity remains one of the most serious risks in wastewater networks. It develops when sewage is retained in anaerobic conditions (lack of oxygen), most often within rising mains (outlet pipe work). The resulting hydrogen sulphide (H₂S) is corrosive, odorous, and presents real safety risks for operational teams.

Design decisions that increase retention time directly increase this risk. In our experience, septicity is rarely a theoretical problem; it is an operational one, with real cost, safety, and reputational consequences.

Evidence, Not Assumption

Focusing upon system efficiency is correct, yet efficiency is not just about the running and life costs of a system; it also means the effectiveness and suitability of the apparatus installed.

This is where our experience adds value. We understand how assets behave in the field, not just how they perform in a calculation.

Simply increasing the rising main internal diameter from 80mm to 100mm increases the retention volume of the main by a staggering 56%.

With evidence now captured, we have proven there is less than 18% of the specified volumes, stipulated within industry guidance, passing through our sewage network via pumping stations.

Pump Selection Informed by UK Network Performance

Our pump and impeller recommendations are based on performance across UK wastewater networks.  Four-pole vortex pumps consistently provide the most robust solids-handling capability in real applications, over alternative, high-efficiency options such as channel impellers, which are proven to block and fail within the UK sewage environment.

For operators and contractors, reliability always outweighs marginal efficiency gains.

Designing for the Whole Lifecycle

Water authorities, NAVs, and contractors work with T-T because we design for the entire lifecycle of the asset, not just adoption compliance.

DCG (Design Construction Guidance) ensures post-adoption standards are met, and we equally focus on the developer's journey before adoption. This time period is often where avoidable risk, maintenance cost, and developer dissatisfaction arise.

Our role is to help eliminate those issues before they are built in.

A Partner, Not Just a Supplier

Everything we advise at T-T is based on recorded data, operational experience, and demonstrable outcomes. We support designers, contractors, and water authorities by challenging assumptions early and ensuring assets perform as intended long after installation.

That is why our partners trust us and why working with T-T results in better-performing, lower-risk wastewater infrastructure.

Speak to the Experts

If you are reviewing a wastewater design, facing adoption challenges, or want to reduce long-term operational risk, we’re happy to help. Call us on 01630 647200 or email: pumpingstations@ttpumps.com.