Severn Trent Water (STW) is interested in hearing from suppliers who have experience in pressurised pipe cleaning and would like to discuss their requirements further ahead of going out to tender with a formal contract notice in 2025.

The water company is seeking to improve its ability to cleanse pressurised wastewater assets rising mains (RM) and clean water mains to address potential problems within its asset base - Severn Trent has issued a Periodic Indicative Notice (PIN) setting out its requirements.

Failure to clean the mains could otherwise result in wastewater assets presenting with rising main blockages, asset failure and lead to further problems such as blockages/pollution/sewer flooding.

Within the clean water network cleaning is to remove biofilms and the risk to water quality.

STW says that part of the solution to achieving this goal is to have a way of cleansing these pressurised pipes which, in some instances are over 500m long and only have one means of insertion and one means of extraction which is sometimes around 2km away.

Currently the water company does not have a similar solution within the business and is looking to explore delivery solutions as part of this pre market engagement.

Severn Trent says it would like to move into a proactive space for asset cleansing without causing disruption through asset failure.

The PIN sets out an overview of the utility’s requirements, including the following assumptions and constraints:

• Wastewater rising mains are generally 80mm to 400mm in diameter and lengths typically range from ~500m to 2km, with some being 5km. They generally only have one access point on the RM and the intention is to cleanse the pipe without the need to cut in every 50-200m as would be required with traditional jetting techniques.
• Connection points such as bower couplings and/or air valves are assumed to be present near the wastewater sewage pumping station (SPS) to allow insertion of pipe cleaning. Basic adjustments will be the responsibility of the contractor i.e. connection to or removal of bower, but significant adjustments of pipework will be the responsibility of STW.
• The pipe material will have been identified prior to cleansing and it is expected that the cleansing will work on the majority of pipe materials. Asbestos may require additional H&S measures, and ductile iron mains, which typically experience galvanic corrosion may be excluded.
• Flow and pressure (or assumed) will be provided prior to cleaning works and work is expected to be carried out within acceptable limits to prevent the cleansing works as not to risk, bursting the main.
• Assets along the rising main length will be identified where present, especially where the RM length is >500m, although it is assumed that any assets do not have isolation valves present on the RM itself, rather only on the spur so unlikely to be of use for insertion/extraction. Where present these will be identified. Air valves should have been inspected/serviced prior to cleansing.
• Rising mains will have been selected for cleansing on the basis there are restrictions assumed to be as a result of blockages / sedimentation, which the cleansing will remedy.
• Flow management of existing flows to the SPS will be an important consideration. Solutions where the rising main can be kept in service are preferred, although solutions where reduced tankering can be used, or even isolation of the main itself for the duration of the cleansing. Flow management is the responsibility of STW unless otherwise agreed.

Customer management and traffic management will be the responsibility of Severn Trent. For clean water sites, it is assumed that STW operatives will isolate the sections of pipe prior to cleansing who will also ensure the area is rezoned accordingly to ensure or customers are informed as necessary.

Following the cleansing of a water main, STW will take water quality samples to prove the main holds water that is 'good to drink', no taste & odour concerns, no chemical or biological residuals on the main before a return to service.

Contractors will be responsible for Health & Safety and will comply with STW safe systems of work including confined spaces, where necessary. Extraction of waste arisings will be undertaken by the contractor so that the arisings do not pass down the system. Where the rising main discharges into a trunk sewer that goes directly to a large works this requirement may be forfeited.

The contractor will be required to provide a written report within 2 weeks of completion with a description of the works, photos and results which will be cross referenced with STW flow & pressure readings to demonstrate the benefits.

Benefits must be demonstrated via the following Minimum Viable Product (MVP) criteria:

Improvement in flow:

The cleansing of the rising main must produce improvements in flow, (Reduction in pressure) and/or reductions in pressure.

Sediment removal:

The cleansing should demonstrate removal of arisings at the discharge.

Flow/Pressure one week on:

The improvement in flow/reduction in pressure should last more than 7 days. Failure to do so would suggest that cleansing is not the root cause of performance, rather pump issues, trapped air or other.

Water Quality (Clean only):

Reduction in coliforms (or other water quality metrics).

The water company expects to go out to tender with a formal contract notice at the beginning of June 2025.

Suppliers interested in discussing further should contact Joanna Benson Senior Category Manager at Severn Trent via email - This e-mail address is being protected from spambots. You need JavaScript enabled to view it .