Water and wastewater services for Kent, Sussex, Hampshire and the Isle of Wight
Your area

Find out if you're a Southern Water customer, check your water quality, or explore our interactive map to see what's going on in your area

Gaters Mill trunk main installation

A new trunk main has been laid along the A27 Mansbridge Road in Southampton from the junction at Wide Lane to Mill Gardens. The work is part of our wider water resources programme and the new pipe will be used to transfer water to our customers in the Hampshire area.

Latest information and project update

The water main has now been installed and tested. The final connections will be made early in the new year, which will require some traffic management at Wide Lane roundabout.
We apologise for any inconvenience this may cause and would like to thank you in advance for your co-operation and patience.


The pipeline has been laid eastbound on the A27 Mansbridge Road from the junction with Wide Lane to Portsmouth Water's Gater’s Mill Water Supply Works.

The route included laying sections of the pipe beneath the M27 and River Itchen, utilising specialised ‘no-dig’ technology.

The works on the A27 are managed by traffic lights in managed sections agreed with highway authorities. This enables the work to be completed safely for the protection of our workforce and the public. The work is completed with extended working hours agreed by the highway authorities and environmental health. 

There may be some disruption to road users, to minimize this we are using the following strategies and equipment:

  • Manual control of traffic lights at peak hours
  • Phased system that matches the flow of traffic
  • Three way lights at busier junctions
  • Filter signs for smaller junctions
  • Equipment to maintain access for residents
  • Hourly site checks 
  • Protocols to be agreed with highways authorities in the event of disruption to the adjacent M27.  


Southern Water’s 711,000 customers in Hampshire, including in Southampton, Winchester, Romsey and Eastleigh as well as the Isle of Wight use an average of 90 million litres of water every day.

Approximately 60% of that water comes currently from the River Test and the River Itchen, with the remaining 40% coming from underground aquifers associated with the River Itchen.

The Habitats Directive now limits the amount of water we can take from the River Itchen in times of extreme drought, to help protect the river’s ecology.

We need to balance this reduction with an increase in the amount of water taken from other sources and to provide a better balance for the environment and customers.

Therefore we are installing a new pipeline from Moorhill to Otterbourne to transfer up to 15 million litres of treated water a day from Portsmouth Water.

The new water main will be laid from Portsmouth Water Gaters Mill WSW (water supply works) to Southern Waters Moorhill to Otterbourne water trunk main in Hampshire to serve Southern Water’s customers in South Hampshire. The work will form part of Southern Waters South Hampshire water resource plan and wider water mains renewal program taking place throughout the region.

We are currently planning to install 1.4km of 450mm ductile iron pipe.


We are working with Archaeology South East to preserve our past

There's more to laying a water main than you might think. When a trench is dug across a road or even through a field it can sometimes reveal the evidence of ancient communities and fragments of time long since buried. That's why at Southern Water we work closely with Archaeology South-East to ensure that our digs are closely monitored to preserve any findings. 

Our work to lay a new water main along Mansbridge Road in Southampton is a good example of how we are working with Archaeology South-East to analyse and record our excavations. 

The archaeological potential in the immediate area is significant. A settlement at Swaythling is first recorded in AD 909. Two mills are also recorded in the Domesday Survey of AD 1086, possibly located in the vicinity of later mills at Woodmill and Gaters Mill. We also know that a medieval manor house is known to have stood in close proximity to the western end of the scheme prior to its demolition in the 1970s.

But it's not just evidence of historical communities that we can discover as a result of our works. The analysis of the earth taken from a bore hole in the area revealed a peat deposit adjacent to the River Itchen which formed approximately 9,000 years ago in the Mesolithic period and continued to develop to approximately the 16th century AD.

"Working closely with Southern Water at an early stage in the design process is important in order to assess the risk of encountering known and unknown heritage assets," says Neil Griffin, project manager for Archaeology South East.

"Any archaeological findings are documented in a site-specific report which is submitted to the appropriate County Record Office and provides a valuable and accessible record of the discoveries made and increases our understanding of past human activity in each particular area."

"We will maintain a continual watching brief over the scheme once the excavations reach the areas of interest."

So the next time you pass the works on Mansbridge Road in Southampton, you may very well be passing a piece of our history hidden metres below your feet.

  Close box