Introduction

Save Windermere has compiled this report to consolidate evidence and historical information on suspected areas within the Windermere catchment that are not connected to the mains sewerage system.

The purpose of this desktop study is to identify where non-mains systems are likely contributing to environmental and amenity issues, particularly in locations where population fluctuations and increased demand place additional strain on local infrastructure. These insights will help inform targeted interventions as part of Save Windermere’s mains connection campaign which has received funding from Patagonia.

Our initial approach will be highly focused, prioritising projects with the greatest potential to deliver environmental benefits in the most vulnerable areas of the catchment.

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Background

Windermere, England's largest freshwater lake, is often described as the "jewel in the crown" of the Lake District National Park. Spanning 10.5 miles in length, one mile at its widest point, and reaching a depth of 64 metres, it was formed 13,000 years ago during the last ice age. The lake holds significant national and international importance due to the rare and protected species it supports, including Atlantic salmon, Arctic charr, and European river eel. It also has cultural significance, as its catchment was home to iconic figures such as Beatrix Potter and William Wordsworth.

Windermere plays a critical role in both the local and national economy, contributing approximately £750 million annually through tourism. However, concerns about its water quality have intensified in recent years, with Save Windermere leading efforts to raise awareness and produce scientific evidence to demonstrate the impact of sewage pollution and other threats to the lake. The campaign has drawn attention to regulatory failings and United Utilities’ (UU) role in endangering Windermere’s ecological health.

Key Issues Facing Windermere

The sustainability of Windermere is threatened by multiple factors, with the most significant impacts being:

Sewage Pollution Promoting Algal Blooms

Sewage discharges are the primary contributor to nutrient loading—particularly phosphorus—in the lake, fueling algal blooms that smother aquatic life and pose health risks to lake users. Phosphorus acts as a fertiliser for algal growth in aquatic ecosystems. While interventions in the catchment resulted in some phosphorus reductions in the 1990s, algal biomass remains a persistent issue that will be further accelerated as a result of climate change. Deep-level oxygen concentrations continue to decline, underscoring the need to tackle the root cause of pollution rather than focusing solely on mitigation. In its natural state, Windermere is classified as an oligotrophic lake, meaning algal blooms would be rare or non-existent without anthropogenic pressure.

Pressure on Local Infrastructure

Research conducted in partnership with Save Windermere and Map Impact, supported by the UK Space Agency, has shown a direct correlation between visitor numbers and algal spikes. This highlights the urgent need for infrastructural improvements to alleviate pressure from increasing visitor numbers on Windermere’s freshwater ecology. The existing infrastructure is not fit to manage the National Park’s rapidly fluctuating population. This is largely due to limitations in rural wastewater treatment technology and additional constraints, such as development restrictions within a National Park and UNESCO World Heritage site. Data from this scientific study indicates that peak population loading in the Windermere catchment has exceeded 300,000 individuals on single days in recent years. The predominance of day visitors introduces significant variability, making it challenging to accurately model and accommodate population-driven fluctuations in wastewater treatment capacity.

Climate Change

Windermere’s ecology is under increasing stress due to a rapidly changing climate. Over the past 70 years, the lake’s mean annual surface temperature has increased by 1.7°C. In the absence of sustainable, elimination-focused nutrient management, this climatic pressure is accelerating the lake's progression toward a critical ecological tipping point. Elevated temperatures are expected to intensify algal proliferation during prolonged calm and dry conditions, while increased frequency and intensity of rainfall events will exacerbate point-source pollution. Additionally, the prolonged duration of thermal stratification is heightening the risk of hypolimnetic oxygen depletion during summer months. The complete elimination of sewage inputs is essential to mitigate microbial decomposition of organic matter—such as sewage-derived suspended solids—which contributes to organic loading, promotes algal blooms and further accelerates oxygen loss in the lake’s deeper layers.

Sources of Phosphorus Input

Phosphorus enters Windermere predominantly from three primary sources, with wastewater discharges representing the most significant and pressing concern. Historically and at present, sewage effluent constitutes the largest single source of phosphorus input to the lake system.

United Utilities (UU)

Both United Utilities and regulatory bodies have acknowledged that treated and untreated effluent from the company’s infrastructure represents the principal source of phosphorus pollution in Windermere, both historically and at present. The scale of these discharges significantly surpasses other point-source inputs within the catchment, owing to the high population equivalents served by United Utilities’ extensive wastewater infrastructure. While existing data supports this assessment, substantial data gaps remain, and targeted monitoring of these assets would likely reveal an even greater contribution from these effluent sources. This highlights the urgent need for enhanced monitoring, data transparency and regulatory oversight. For example:

Monitoring of treated effluent relies primarily on operator self-monitoring data, a method that has faced criticism due to concerns over potential bias and lack of independent verification.
Real-time monitoring of phosphorus concentrations is currently conducted at only one of United Utilities assets within the Windermere catchment, and initial requests for public access to this data were denied.
Estimates of untreated sewage discharges are based on a proprietary model that lacks transparency, with critical parameters—such as effluent volume and phosphorus concentration—omitted, thereby raising questions about the model’s reliability and robustness.
Sewage effluent is a major source of dissolved phosphorus, a bioavailable form of the nutrient that is rapidly assimilated by algal communities, particularly during the warmer summer months.

Non-Main Drainage Systems

Non-main drainage systems contribute to nutrient loading in Windermere, primarily due to inherent technological limitations that prevent them from effectively treating effluent to standards that won’t impact the lake’s ecology. Assessments by the Environment Agency and other bodies regarding the impact of these systems are not grounded in systematic field sampling, raising concerns over the accuracy and reliability of current estimates. Despite the uncertainty, the prevalence of such systems across the catchment suggests their cumulative impact is likely to be non-negligible. Addressing this issue is therefore essential to ensuring the long-term ecological sustainability of the area and safeguarding Windermere’s long-term environmental integrity.

Numerous businesses within the Windermere catchment are heavily dependent on tourism, resulting in pronounced seasonal variability in population loading. Many of these establishments operate with limited or outdated private wastewater treatment infrastructure, heightening the risk of water quality issues in Windermere during peak demand periods.

Agriculture

Save Windermere maintains that agricultural interventions will not deliver significant or rapid reductions in nutrient loading, as the catchment lacks practices typically linked to excessive inputs—such as arable farming, intensive poultry, or large-scale dairy operations. The largest source of nutrients is sewage pollution, and this is where resources must be directed to achieve meaningful reductions.

Satellite analysis shows no correlation between agricultural inputs and algal spikes. Estimates of farming contributions also lack robust empirical evidence, making the emphasis on agriculture unfounded. Sediment-control measures on the fells will take decades to show benefits and are already covered under existing Environmental Land Management schemes. Poor farming practices can be addressed through current regulations, notably the Farming Rules for Water.

While some agricultural contribution is inevitable, interventions to improve water quality are already funded through higher-tier Countryside Stewardship (CS) agreements.

Despite an increasing number of farmers in the catchment enrolling in CS, Environmental Stewardship (ES), and Sustainable Farming Incentive (SFI) schemes, DEFRA reports little to no measureable impact from these schemes: phosphorus input to Windermere remains unchanged at 2,326 kg/year despite a 24% rise in farm enrolment over 15 years. This, coupled with significant reductions in artificial fertiliser use—driven by rising costs and a decline in local livestock numbers—further supports Save Windermere’s position on the limited contribution of agriculture to the lake.

Land-based agricultural interventions are more effective in areas with intensive dairy, poultry, or arable farming—none of which are present in Windermere. While improvements to agricultural practices are important for drought management, biodiversity net gain, and flood management—and should continue to be supported by the government—the primary focus for improving Windermere’s water quality should not be conflated with broader agricultural policy narratives.

Save Windermere's Campaign on Non-Mains Drainage

Due to the issues outlined above, and following Save Windermere’s long standing campaign and success in raising the awareness of United Utilities’ pollution, the group has now turned its attention to the absence of a long-term strategy to eliminate non-mains discharges. Save Windermere has launched a project aimed at effectively communicating and advocating for a sustainable, long-term solution to this issue.

Pollution from private treatment systems has contributed to Windermere’s water quality issues, with United Utilities (UU) attributing 30% of phosphorus loading in the lake to these systems. While Save Windermere challenges this figure due to a lack of ground-truth sampling, their contribution likely remains significant, particularly due to pollution fluctuations at some sites and the technological limitations of private systems which are unable to sufficiently remove nutrients.

A key barrier to addressing this issue is the lack of communication surrounding Section 101A of the Water Industry Act, which grants property owners the right to request a connection to the public sewer system if an existing private sewerage system—serving two or more premises or a locality—is causing or is likely to cause environmental or amenity issues. The process requires the water company to assess options by comparing the costs and benefits of public and private solutions to determine the best approach. If a dispute arises, the Environment Agency acts as an impartial mediator. If the request is approved, the water company must fund the installation of a new sewer to at least the curtilage of the property.

Enabling more non-mains properties to connect to the existing sewer network is essential for the long-term protection of Windermere. United Utilities has access to better wastewater treatment technology, such as chemical dosing to further reduce phosphorus, thus reducing the likelihood of pollution from its infrastructure. This transition aligns with existing legislation and brings us closer to Save Windermere’s ultimate goal: the complete removal of sewage discharges into the lake.

Why Connection to the Mains is the Best Solution

Technological Limitations: Current systems lack the nutrient removal technology necessary to protect Windermere’s ecology. Even if sites are maintained and operated to supplier standards, private owners have very limited capacity to reduce their impact on the lake.

Maintenance Issues: Private systems are difficult to maintain, costly to operate, and place a disproportionate financial burden on individual owners in the long term.

Lack of Regulatory Oversight: Some areas rely on private septic tanks and package treatment plants, which, if poorly maintained, can cause significant pollution. Without a discharge permit, regulators are often unaware of the impact of these systems until pollution is reported.

Fragmented Responsibility: The absence of coordinated management and regulatory enforcement for private systems results in inconsistent standards and oversight.

Sustainable Development: Connecting sites to the mains sewerage network would ensure sustainable development in the area while preventing increasing nutrient loading on sensitive ecosystems.

Regulatory and Financial Context

Section 101A of the Water Industry Act 1991 and the First Time Sewerage Scheme provide an existing framework for transferring responsibility for private treatment systems to water companies.

Funding Allocations

A Freedom of Information (FOI) request submitted by Save Windermere to OFWAT sought confirmation of the funding allocated to United Utilities (UU) since privatisation to fulfil its duty under Section 101A. The request also asked for a breakdown of the total expenditure on connecting non-mains properties to the sewerage system versus the total allowance designated by OFWAT.

OFWAT figures show that since 2000, £129 million has been allocated to UU for connecting non-mains systems to the mains sewer network. However, only £76.7 million has been spent, leaving significant concerns over the funds that remain unutilised as of the date of the data request. Since the early 2000s, UU has completed only one First Time Sewerage Scheme in Windermere, connecting just 27 properties.

Save Windermere believes this lack of progress is due to insufficient public engagement and awareness of this mechanism, preventing eligible property owners from accessing the scheme.

Identifying Key Locations for Connection to the Mains

While connection to the mains may not be a feasible or cost-effective solution for all properties currently operating private treatment systems, a cost-benefit threshold must be satisfied to justify such interventions. Save Windermere advocates for a targeted approach, prioritising systems with the highest potential to negatively impact the lake’s ecological health. Furthermore, the presence of significant clusters of properties within defined localities may strengthen the economic case for connection, thereby challenging the cost-benefit argument against broader infrastructure upgrades.

The following information is based on data obtained by Save Windermere through an Environmental Information Regulations (EIR) request to United Utilities (UU). This data provides a general understanding of the locations of UU’s mains infrastructure and, consequently, areas where no mains infrastructure is likely to exist—indicating a higher probability of septic tanks and package treatment plants in those locations.

By combining this desktop approach with local insights, we have identified areas where pollution issues are most likely to arise from non-mains systems. Save Windermere has made it clear that some areas should be prioritised due to their higher risk of pollution and amenity issues. Our focus is on maximising environmental benefits with limited resources, ensuring that efforts are directed toward locations where they will have the greatest impact.

Refining Our Approach

Given our additional insights, we are also able to assess the accuracy of UU’s maps, which are sometimes outdated. For example, the main sewer was not shown in the provided documentation as extending to Low Wood Bay Hotel, yet other EIR requests confirm that the hotel is connected—making this a lower-risk area.

Similarly, the maps we were provided did not show the existing infrastructure around Ferry House wastewater treatment works (WwTW). However, by cross-referencing this with the list of permitted sites provided by the Environment Agency (EA), we were able to confirm which locations in that area are or are not connected to the mains network, allowing us to refine our targeting approach.

Prioritisation Criteria

To guide our efforts, we have developed a weighted priority criterion based on the following factors:

Significant population influx due to tourism.
Presence of hotels, campsites, pubs, restaurants, or properties with higher-than-average toilet usage.
Density of residential homes in an area.
Properties likely discharging into protected or sensitive environments.
Proximity to popular recreational areas.
Number of properties that could be connected if a new sewer is installed.
Properties with existing discharge permits.
Properties likely discharging directly into a watercourse.
Properties within 1,000m of an existing mains network.
Homes far from a watercourse, where a septic tank with a leach field is more probable—resulting in the lowest impact on water quality.

Mapping and Sub-Catchment Analysis

Map design work led by Emily Pearce initially focused on defining UU’s existing infrastructure to infer likely non-mains locations. Each map is divided into sub-catchments, including:

Ambleside
Grasmere
Langdale
Hawkshead
Outgate
Near Sawrey
Far Sawrey
Troutbeck
Windermere & Bowness

The maps provide a visual representation of key infrastructure and priority areas, including:

Local Buildings – Purple rectangles
Tourism Businesses – Orange circles
Example Route to Existing UU Infrastructure – Yellow line
UU Existing Sewer Network Boundary – Green shaded area
UU Sewage Treatment Plant – Red diamond
Rivers – Thin blue lines
Lakes – Blue shaded areas

This mapping approach helps to visualise the spatial relationships between existing infrastructure, priority areas and proposed feasible connection routes. Only routes that would serve a substantial number of properties are suggested. Detailed engineering cost assessments and feasibility studies for these routes would need to be undertaken by United Utilities.

Key Locations for Connection to the Mains

Based on this study, we have identified the following areas as offering the greatest environmental benefit if a mains sewer were installed. While we have yet to engage with all the areas or businesses referenced here, this assessment serves as a foundation to inform our decision-making process.

Skelwith Bridge

This area has long been a priority for the campaign due to its designation as a notable "honeypot site" with high visitor footfall. Environmental Information Requests (EIRs) submitted by Save Windermere revealed infrastructure-related environmental impacts, prompting engagement with two of the largest businesses operating in the area. These businesses were informed of the mains connection mechanism and encouraged to submit applications to United Utilities. Collectively, they represent the equivalent of 105 properties and one site sees approximately 150,000 visitors annually.

Save Windermere is actively advising on this application.

Esthwaite

Esthwaite has been prioritised due to the high level of legislative protection afforded to its water body, which is designated as both a Site of Special Scientific Interest (SSSI) and a Ramsar site. Water quality concerns at Esthwaite Water have persisted for decades, with excessive phosphorus identified as a primary factor contributing to its failure to achieve Good Ecological Status.

Given the limitations of private treatment systems, it is unlikely that they can consistently reduce phosphorus concentrations to levels necessary for the protection and improvement of water quality. In contrast, connection to United Utilities' infrastructure—with tertiary treatment capability—offers the potential for substantial reductions in phosphorus, as well as other pollutants such as suspended solids, ammonia, and excess nutrients that affect dissolved oxygen levels.

Save Windermere is actively engaging with residents in the area and has already supported the submission of one application.

Holbeck to White Cross Bay

This area became a focal point of the campaign following discussions with the owner of Holbeck Ghyll Hotel, where it was clear to Save Windermere that the business had undertaken significant measures to reduce its environmental impact and protect the lake. However, despite these proactive efforts, the broader environmental pressures on Windermere remained unresolved.

The locality includes a hotel and 15 residential properties connected to a single private treatment system, underscoring the potential environmental benefits of a mains sewer connection. As the campaign progressed, Save Windermere expanded its focus to the surrounding area, identifying the relevance of a prior feasibility study undertaken during AMP5. This study, conducted by United Utilities, examined the technical and financial feasibility of connecting approximately 100 domestic properties and six hotels between Windermere and Ambleside to the public sewer network.

The project—estimated in 2015 to cost £7–8 million—demonstrated that such an initiative was both viable and environmentally beneficial with appropriate investment. Nevertheless, the scheme was never implemented.

A key concern for the campaign is the Brockhole Visitor Centre, situated between Holbeck and White Cross Bay. Given its lakeside location and high visitor numbers, the site poses a significant risk to water quality. Its effluent discharge volume is among the highest in the catchment, making it a clear priority for intervention. To progress this issue, the AMP5 study must be revisited and brought up to date, alongside the development of a revised cost assessment for connecting Brockhole and potentially adjacent areas to the mains sewerage network.

Great Langdale Valley

Great Langdale Beck is one of the highest-quality watercourses in the catchment, supporting a diverse range of species. However, ongoing environmental pressures, including inputs from non-mains drainage, could threaten its ecological health. Save Windermere’s invertebrate sampling programme has confirmed the presence of sensitive riverfly species, highlighting both the beck’s importance and the need for targeted interventions to prevent degradation and further enhance water quality.

The most significant environmental impact in this area originates from National Trust businesses located at the head of Langdale Valley. This presents a unique opportunity for intervention, as the primary locality suitable for mains connection lies at the head of the valley, while 99% of additional properties are situated along the suggested route for a new main sewer. The beck ultimately flows into Elterwater, which is a Site of Special Scientific Interest (SSSI).

The strategic importance of this area is clearly illustrated in the accompanying map, which highlights it as a priority site for connection to the mains network. Save Windermere has already had positive discussions with stakeholders in the area regarding potential solutions.

Troutbeck

Troutbeck has been identified as a priority area by Save Windermere due to its ecological importance as the third-largest river feeding into the lake. Analysis of infrastructure maps suggests that a substantial number of residential properties are located along the main road traversing the valley. This linear configuration provides a compelling case for mains sewer connection, as it would allow for the efficient inclusion of multiple homes and businesses along a single route. The area also experiences significant seasonal visitor pressure, evidenced by the presence of key tourism sites such as the National Trust’s Townend property and the Limefitt Caravan Park.

Save Windermere strongly recommends that United Utilities explore options for connecting this locality to the existing infrastructure that conveys effluent to the Windermere Wastewater Treatment Works (WwTW). The current wastewater infrastructure serving Troutbeck village—essentially a package treatment plant operated by United Utilities—is inadequate to ensure long-term environmental protection. This system has already been linked to environmental and amenity concerns, including pollution incidents involving poorly treated effluent and the presence of sewage fungus in the receiving watercourse.

Rydal

The area around Rydal shares many characteristics with Skelwith Bridge, making it a strong candidate for a first-time sewerage scheme. Following discussions between Save Windermere and United Utilities (UU), it became clear that UU also recognises this opportunity, as Rydal was included in their 2024 high-level engineering assessment for long-term infrastructure investment in Windermere.

We support further exploration of this option due to the presence of several businesses in the area that experience seasonal population fluctuations. Additionally, this scheme would help protect the River Rothay, which is already under significant nutrient loading and environmental pressure from Grasmere WwTW. Reducing the point source burden downstream of Rydal Water would provide significant ecological benefits.

Little Langdale

Little Langdale experiences significant population fluctuations due to its proximity to two major visitor attractions: Blea Tarn and Cathedral Cavern. Both sites are widely promoted on tourism websites, drawing high footfall to the area.

The locality includes a pub/hotel and holiday cottage facilities, further contributing to seasonal variations in wastewater demand. The nearest United Utilities connection is Langdale Wastewater Treatment Works (WwTW), approximately 2.6 km away, following the main road route. Given the visitor numbers and existing infrastructure, Little Langdale presents a strong case for further assessment of mains connection feasibility.

Tower Wood, Fell Foot and Lakeside

The south basin of Windermere remains a significant concern due to its lack of mains sewage infrastructure and shallower depth, making it more vulnerable to climatic pressures. Over five miles of shoreline, including residential properties, holiday accommodations, and tourism businesses, relies entirely on non-mains drainage systems, posing an ongoing risk to water quality.

Despite the clear environmental threat, there has been no significant investment in infrastructure expansion, leaving properties dependent on unsustainable septic tanks and private systems. The cumulative impact of these dispersed discharges contributes to nutrient loading, exacerbating algal blooms and ecological degradation.

Section 101A of the Water Industry Act 1991 offers a mechanism to facilitate mains sewerage installation, yet previous feasibility assessments remain unimplemented despite demonstrating the viability of large-scale mains expansion. A reassessment of the south basin’s infrastructure is essential to determine the cost and feasibility of connecting priority areas to the mains network.

Save Windermere has already engaged with local residents who were previously unaware of this mechanism and are now exploring their options.

Quick Wins

Given the close proximity of certain properties to existing infrastructure, Save Windermere believes that targeted interventions could be implemented with minimal additional investment.

In several areas, it is surprising that mains connections have not already been established, despite their immediate proximity to the network. For example:

A cluster of properties between Troutbeck Bridge and Rayrigg Road appear to be unconnected, despite running parallel to the mains.
Along the Bowness to Newby Bridge road, at least 100 properties are estimated to be near the mains but remain unconnected.

These gaps highlight opportunities for improving wastewater management, assuming United Utilities' (UU) maps are accurate and up to date.

Save Windermere fully recognises that businesses operating in these areas are not responsible for the lack of mains infrastructure, and our campaign is not a criticism of them. In fact, many have taken significant steps to minimise their environmental impact. Our focus is on advocating for systemic improvements to wastewater management, ensuring that tourism—an essential part of the local economy—can continue sustainably without contributing to water quality issues.

Fell Foot

Fell Foot, located at the southern tip of Windermere, is a popular National Trust tourist destination and one of four designated bathing water sites on the lake. The site experiences substantial seasonal visitor fluctuations and is served by private wastewater systems that are not adequately equipped to remove microbiological contaminants. Historically, elevated levels of coliform bacteria have been recorded at this location.

On 25 May 2022, a water sample taken at Fell Foot detected Escherichia coli concentrations of 4,600 CFU/100ml. Similarly, on 27 July 2022, a sample from Lakeside YMCA—another non-mains drainage site within the south basin—recorded 1,500 CFU/100ml. While isolated results such as these may not individually trigger a failure under current criteria for "Excellent" bathing water classification, mainly due to limitations in the methodology used to assess Bathing Waters, they nonetheless highlight significant public health concerns. Particularly, the 4,600 CFU/100ml result underscores the potential risk of exposure to faecal contamination in recreational waters.

Additionally, an increasing trend of E. coli values at Fell Foot further underscores the need for action:

2021: 90 CFU/100ml
2022: 197 CFU/100ml
2023: 223 CFU/100ml

These findings highlight the urgent need for connection to mains sewerage infrastructure, where United Utilities could implement UV treatment to significantly reduce coliform concentrations in treated effluent.

Windermere Jetty Museum

Despite its proximity to the mains network and high visitor numbers due to its location on the lake shore, Windermere Jetty Museum remains unconnected to mains infrastructure. This presents a significant opportunity for a low-cost intervention that could improve wastewater management in a high-footfall area with relatively straightforward intervention.

The Samling Hotel

The Samling Hotel presents another quick win due to its proximity to existing mains infrastructure. The main sewer, which connects Low Wood Bay Hotel to Ambleside WwTW, runs via a rising main near the hotel. Despite being parallel to the mains sewer, the hotel operates a package treatment plant under a discharge permit enforced by the EA.

Save Windermere is also aware of an existing application from a residential property in this vicinity. Therefore, we propose that United Utilities explore the possibility of expanding any potential work required in this area to incorporate additional properties.

Conclusions

Based on the findings of this desktop study, Save Windermere has undertaken a series of targeted actions within the identified priority areas. These include:

Presentations to key stakeholders
Engagement with local parish councils
Advising residents on available wastewater management options
Disseminating detailed information to raise awareness and encourage viable solutions

If you are interested in submitting an application for connection to the mains under Section 101A of the Water Industry Act 1991, Save Windermere has prepared a comprehensive guide to assist you through the process. This guide outlines eligibility criteria, benefits of connecting to the mains, and step-by-step instructions for application. You can access the full guide here.

For further information on dispute resolution regarding public sewer connections under Section 101A, the Environment Agency provides guidance here.

These resources are intended to support you in navigating the application process more effectively and in contributing to the broader efforts to safeguard Windermere’s water quality. If you have any questions or require further assistance, please do not hesitate to get in touch.