Councillor Adam Boyden

Somerset County Councillor for Frome North and Mendip District Councillor for Frome College ward (Lib Dem) Learn more

Survey reveals extent of fly nuisance experienced by residents around Frome sewage works

by adamboyden on 8 April, 2022

Some 128 people have responded to our survey into the fly nuisance around Wessex Water’s Frome sewage treatment works over the last few weeks, after I and other councillors (Janine Nash and Damon Hooton) and local residents Lee & Michelle put leaflets and letters through hundreds of letterboxes in houses to the east, south and west of the treatment works in late February and early March. A summary of the results collected online and in hard copies delivered to the Freepost address, is below, relating to each question in the survey:

1. Do you sometimes experience large numbers of flies in and around your property? Some 94% (120 people) had experienced large numbers of flies in and around their property, only 8 had not.

2. How many flies do you experience at any one time? Residents experienced hundreds (38%), thousands (35%), millions (10%), a few (3%), or dozens (17%) of flies at any one time, or it varies (16%).

3. Roughly how many days has there been a fly problem in the last 12 months? Responses varied – for some it is every day, for others ‘mainly in warm or mild weather’, ‘all summer’ or ‘a few’.

4. Do you remember any specific dates it was a problem? Most people could not remember specific dates. Responses included spring, summer, autumn, and the recent mild winter including late February. Specific dates mentioned were May and June 2021, August Bank Holiday, Christmas and New Years Eve and Day 2022, early February, 15th, 17th-22nd and 27th February.

5. Is there any time of day when it is worse? People ticked multiple times so the proportions do not add up): So afternoons and evenings are generally worse.

6. How much of an impact does this have on your life and the use and enjoyment of your home?

I assume that a moderate, major or slight impact could all be defined as a nuisance, so 111 people, 86% of those responding, have reported what could be described as a nuisance.

7. How would you describe any fly problem and how it affects you? 

This is where the value of this survey comes alive – people’s real descriptions of the problem in their own words. When describing the fly problem, many people complained of:

  • large numbers of large window gnats Sylvicola fenestralis, and black midges Chironomidae
  • not being able to open any doors or windows even when it is warm (an obvious problem in a Covid pandemic, or with any damp in the house) because large numbers come in the house
  • not being able to enjoy the garden with swarms of flies around, and flies covering garden walls
  • seeing swarms of flies during the day, like a small hazy cloud, at the side of a large conifer tree by the sewage works (helical mating swarm – see photo below), and in other trees
  • flies getting in food and drinks, even in the fridge
  • flies in the bathroom, and children’s bedrooms, in washing machines
  • flies getting in any room with the light on in the evening or at night
  • some people unable to keep flies out of the house at all, even with doors and windows shut, as they find a gap or vent
  • if leaving the house is necessary in the evening, having to turn all lights off, rush out with mouths closed, and rush in again, before they get in
  • having to vacuum them off walls and ceilings, and sweep up in the morning
  • being embarrassed to invite or entertain guests
  • flies leave dirty marks on windows and paintwork.
Source: Wessex Water, 2021, Frome Fly Management Plan (version 8)

Some of the worst comments are:

  • They are everywhere in the spring and summer. They get in the house, including in the fridge and on our food. We can’t open doors or windows when it is hot. We have to turn off lights when we enter + leave the house to stop them coming in. We cannot play outside with our children in the garden when it is bad. Our kids find them in their rooms at night. We have blinds up on every door and window.
  • “In the garden it can be difficult at times to breath without inhaling them If any of our windows or doors are open when it’s bad they swarm in and gather in certain areas often then dropping when dead especially in the kitchen and bathroom. I often find many dead flies on my draining board but the worst is when running the bath I have to have the window open to avoid condensation. By the time my bath is run it has many dead flies floating in it as they gather above it.”
  • “They get in your eyes and throat. Even just walking up and down the path from home. They are around and in food. The fridge. The washing up. When they die they stick to the wall and decompose leaving marks.”
  • “Major at high season, can’t sit outside, is in kitchen, drinks, food, windows covered. Can’t have lights on as it attracts them. Bedrooms on bed or around us. Bathrooms in towels, shower, anything damp. Grandchildren hate them. Can’t have food on dining table.”
  • “Not being able to have doors or windows open, even when it’s very warm. The flies invade especially at dusk. Not being able to enjoy the garden because it can be covered in flies.”
  • “There are just thousands flying about, front and back of property, they are always in the windows and most annoying of all, is when you are doing food and they drop into it! Even with the windows shut, they still manage to get in.”
  • “Living across the river from the sewage treatment works, we suffer from the invasion of flies. Some years are worse than others. We have lived here for 35 years. Sometimes an entire outside wall of the house gets covered in flies so it looks black. The flies spiral above trees along the river every year. If you have any doors and windows open you find the mosquito type flies in the kitchen, in the fridge, on the worktops, down the toilets, in the sinks, on the windows. It is a real problem.”
  • “Really really annoying. You cannot leave the windows or door open at the time when the flies tend to swarm. Leaving a light on is even worse. It can be up to a dustpan full at a time.”
  • “The black midges and flies come over from the sewage works in enormous swarms. Most of the residents just feel we have no choice but to put up with it.”
  • “We are unable to open our back door without hundreds of flies entering our kitchen. They land on surfaces, on the fruit bowl, on food and drinks being prepared. We have even found them in our fridge and washing machine. Lately I have also found them inside my car. Our garden is also becoming an ‘out of bounds’ area due to the swarms of flies thus restricting mine and my childrens’ access to our own gardens.”
  • “Flies inside appear from nowhere. We live in a modern house with double glazing. I just don’t know how they get in. They then cover the walls and then die overnight so we have piles of dead flies. Outside it has been so bad at times I haven’t been able to go into the garden – I just inhale flies. They swarm in huge clouds.”
  • “The flies are disgusting, they go in your mouth and up your nose, in your eyes. You can’t open your windows & door as they land in your cup or your dinner. Summer is even worse , they get everywhere making a mess. You can see the clouds of them going around up and down the trees. They go on your washing, and spoil time in the garden. One day my brother in law was coming along the road and a cloud of flies drop on to his windscreen and he had to put his windscreen wipers on so could be very dangerous. All in all it’s horrible to have them affecting all our lives. Some days are worse than others.”
  • “The flies are in swarms all around the house. At night when the lights go on in the house they all try to get inside. Our back windows and door are plastered with dead flies all the time that we continually have to clean off. It means we can’t really sit and enjoy our garden in the late afternoon and into the evening as they are everywhere.”
  • “Flies collect around doors and windows, meaning we are unable to open any on a hot day. and if we accidentally do so the house is infested. we are also unable to spend time in the garden due to the fly problem. I Don’t believe Wessex are doing enough and DO NOT keep good enough house keeping at Frome WRC.”
  • “We are not able to open doors or windows at any time of year. We will genuinely get swarms of flies come in. We are not able to use our garden in the summer. We are embarrassed to have guests over as they question our hygiene even though we can’t avoid. We have spent a fortune on fly screens and fans as we can’t open windows. We have to cover our cat’s food otherwise flies lay eggs in her food.”
  • “The flies appear early in the year and it continues until winter. There are clouds of them (outside – and even get in the house through shut windows. We have complained to our MP, Sewage Works and Environmental Health for years. Last year the council told us to keep the windows shut – it was summer and Covid! The Sewage Works visit when we complain but pay lip service! MP says investment is needed but no money available! Wessex Water say they can’t use sprays because of the environment. What about our right to a clean environment. It is absolutely revolting. Washing covered in them, air pollution, etc, etc!! Cannot leave doors & windows open.”
  • “Cannot open windows and as a result of this we have mould growing in bathroom. Flies are in our food when cooking. All caked around back of cooker and the fan. Cannot keep cat food out for long as they grow white eggs so cat won’t eat. Having to hoover up walls daily. Cannot keep indoor plants as they breed in the soil. Children find it hard to even play in the garden as they swarm around there. We have found them in the food in the fridge and also on the fruit and veg left in baskets. We live directly outside the tree and sewage works so we can see the swarm from my bedroom window.”
  • “To be honest I think it’s disgusting and not acceptable in the 21st century. We have lived on … for 30 years and it was never a problem, so what has changed? Initially we only suffered with the ‘window knats’ which only appear in the summer. They’re in the fridge, in your cooking, in your face and congregate on the windows. If you fly spray, you sweep them up in dustpan fulls. Fortunately most of these disappear. The small black flies that swarm are continuous these days. They are attracted to the laundry on the washing line and stick to it, when you open the car door, they follow, if you talk whilst walking, they go in your mouth, in your hair and behind your glasses! They’re always around lights in the house and particularly bad in the winter when you open the front door to a lit up house. We watch them swarming around our chimney stack from an unopened velux window upon which they copulate. Our outside light is brimming with them. I could go on…”.
  • “We cannot open our front windows as our ceilings and walls become infested with thousands of tiny black flies, which take ages to hoover up. We can sometimes open our rear windows, but not in the evening. Most evenings you can see thousands of flies on our windowsills. I love gardening, but some days (particularly mild damp days) it’s horrible as there are swarms and you end up getting them in your eyes We’ve only lived on … a year, and have been plagued by these tiny flies since moving in.”
  • “Hundreds of small midge-like insects are like a cloud of black at the bottom of our garden (nearest end to sewage plant), and on our kitchen ceiling. The flies then die and drop onto our kitchen work surfaces. Extremely unhygienic in a room where food is stored and cooked”.
  • “They fly into your face. They swarm in packs around plants and guttering. Clouds of midges can be seen in the sky and around trees. Can’t open windows. They fly in when you open the front door.”
  • “We have small flies congregating near lights at night, flying in the house in hundreds and thousands as soon as a door is opened. We have to turn lights off before opening doors. We cannot open windows in the summer or the house will fill with flies in minutes. The gardens full of flies, crawling up the walls and fences, all over the windows in the summer. It’s horrendous at times.”
  • “The worst fly days are on mild winter days for non biting midges and in April/may for the window gnats. The non biting midges are attracted to light so you cannot have windows or doors open so cannot air the house and if you need to go out you have to open and close doors very quickly to avoid having significant numbers of flies in the house. The window gnats fly in when doors and windows are open (not attracted to light) so on a warm spring day you cannot have doors or windows open. Both types get everywhere in the house, they get in food, on clothes, and buzz around your head and face. With 2 small children I am very concerned about the disease they carry especially given where they come from. They make the garden unusable on a bad fly day. When I have been decorating I have ended up with lots of flies stuck to newly decorated surfaces. I spent £2000 installing an internal door to my property to avoid having to open am external door as it let so many flies into my kitchen. The anxiety I experience from the nuisance caused by the flies impacts on my mental health. They’re gross, they’re relentless and they do not seem to be going away.”
  • “It is a nightmare – you cannot have doors or windows open – if you sit in the garden they are everywhere It is very upsetting.”
  • “Every time we open a door or a window they are in. It is much worse during the evening and at night. They are attracted to any light source. To combat some of the problem we have had to fit a fly screen to the back door of the house, as we have a dog that needs letting out. They still manage to get in though. Also we gave up on ordinary lamp shades as everyday there would be alot of dead flies on the floor. They even seem to find their way into the fridge. When we first moved here 21 years ago they only seemed to be two periods of the year when we suffered with this problem, which were March/April and September/October. In recent years it has definitely increased.”
  • “Can’t keep windows open, as a result the house suffers from damp and mould from condensation. In summer, it’s unhealthy to keep the house so closed up. I have spent a lot of money having bug screens made for doors and windows for this coming season.”
  • “I lived in … for 8 months. The flies were awful. Disgusting. I moved out and will never go back to that part of town. Looked at buying a house there recently and decided not to because of flies. Wessex Water needs to sort it out. Telling people to close windows is not good enough.”

8. Do you have any evidence of any problem? Most people did not have current evidence, but nearly a third did, mainly photographs.

9. Are you willing and able to collect any evidence if flies appear again in future?

71% said Yes, 11% No, and 18% Yes with help. Help and advice will need to be provided.

10. Have you complained to anyone about the problem before? (select all that apply): Over tow thirds of people had not complained about the problem before at all, to anyone. Perhaps this is because they did not know who to complain to. Most people who had, correctly complained to Wessex Water and Mendip District Council.

11. Have you had any other communication on this issue recently with:

90% of people had not had any other communication. This was largely before Wessex Water sent out a letter to residents in the affected areas.

12. Has this problem cost you financially, for example things you have had to purchase, or lost income?

Over a third of people responding had incurred costs, some substantial (£hundreds) and 51 comments described these, including:

  • food and drink thrown away – 4 mentions
  • house plants thrown away
  • fly spray, smoke bombs, oils and scents – 21 mentions
  • electric fly zapper / insectocutors – 6
  • fly paper / traps – 6
  • electric fans in every room
  • fly screens and blinds on windows and doors – 14
  • new air conditioning
  • structural changes to provide new internal and external doors
  • a cleaner – 2
  • loss of temporary home rental income while away
  • house price affected

There does not appear to be any current arrangement for Wessex Water customers to reclaim any of these costs. The potential for financial compensation for residents suffering nuisance and costs incurred needs to be investigated.

13. Would you be interested in joining a local residents’ Action Group to share experiences and information, meet other residents, local councillors, the Council/s and Wessex Water, to lobby for further action to improve the situation?

Half the people responding replied yes or maybe.

To the question of taking a lead role, 5 people said ‘maybe’, one said yes, one said they already are (in a group), and one would like to pass on all the research and work they have done to others as they have been exhausted by the situation. One said “Wessex Water say they are looking into it and nothing ever gets done”.

14. Please leave your contact details if you wish to hear back from us about the results of the survey. 

Of the 128 respondents, 117 people left names and contact details. These are being replied to in person or by email. The location of responses and level of nuisance suffered by residents is being kept confidential due to the risk of blight.

Discussion and next steps

The survey results show that a large number of residents in an affected area to the east, south and west of Frome sewage treatment works have suffered nuisance from flies that Wessex Water admits breed in large numbers at the works. 93% of those responding said they experienced large numbers of flies (midges and gnats) in their home and garden, and 86% (111 people) responded the flies were having a moderate, major or severe impact on the use and enjoyment of their home. Residents have responded in their own words how the flies affect living in the area, and many responses are difficult to read. This indicates that residents have been suffering a major nuisance in the area. Previously only up to 16 residents are reported to have complained about flies to either Wessex Water or MDC in any year (see below), which is a small fraction of the number of people suffering the nuisance.

Source: Wessex Water, 2022

Also, while the numbers of people responding was good, many residents in the affected area did not respond, so further surveys and canvassing could be done to gain additional responses.

The results of the survey so far will be sent to everyone who responded, for their review and comment, and then on to Wessex Water, Mendip District Council’s Environmental Health and Housing teams, Frome Town Council and other local councillors, to inform discussions and further decisions by all parties to address the problem. In particular, this should inform decisions by WW and MDC on nuisance abatement measures, discussions at a post-trial meeting with Wessex Water in June or July 2022, and discussions between affected residents.

Residents who responded have been advised who to complain to or contact by the survey letter and also by Wessex Water’s letter to affected areas. Residents will also be asked to keep a ‘fly diary’ and take photo and video evidence on any bad fly days.

The survey reflects the situation at the time residents responded – mainly late February and early March. Further survey of residents could be undertaken again to find out if residents’ experiences have changed during the netting trial (March-June 2022), and to test the effectiveness of any further abatement measures.


Meetings with other residents and councillors had been held in previous years, most recently in May 2021 and in January 2022. I and councillors Janine Nash and Steve Tanner and local resident Lee attended a meeting with Wessex Water at the treatment works on 28th February. A draft note of the meeting has been sent to Wessex Water, and is available on request. We discussed the initial results coming out of the fly survey, and previous studies and commitments.

After the January meeting, Wessex Water had been persuaded by one resident (Joe’s) painstaking and detailed research to install netting over half of the trickle filter beds where the flies breed, to prevent large numbers of flies entering the beds to breed or leaving in large numbers, and to study the effect on fly numbers compared to un-netted beds. The then-current version of the site’s Fly Management Plan (v8) had ruled out the use of netting due to problems with blocking filters and risks to discharge consent compliance, but Joe’s work persuaded them to give it another try, and the Fly Management Plan would be updated and sent to MDC for approval. The Fly Management Plan is available on request.

We discussed how Mendip District Council’s Environmental Health team can serve an Abatement Notice under the Environmental Protection Act 1990 when a nuisance is being caused, to legally compel a company to take action to avoid nuisance, but have not yet done so in this case yet because they appear satisfied the company is already using best practices as set out in the Fly Management Plan. Despite this, the problem persists, hence the need for further action. Private action to abate a nuisance can also be taken by residents through the Magistrates Courts under section 82(1) of the Environmental Protection Act 1990, but this needs good evidence of a problem (such as detailed complaints and testimonies from over 100 residents) to have any chance of success.

We asked how Wessex Water would communicate with residents, and they agreed to write to everyone in the affected area. I provided street names, and letters went out to residents in early March. Wessex agreed to keep us up to date on progress on site, provide further information, and to call a meeting to review the trial results after it ends in June, to which councillors and a (small number of) residents would be invited.

Since the meeting, Wessex have provided additional information requested, including a report of a review in 2019 into fly removal techniques (see below), the results of fly and larvae monitoring, and correspondence from the larvicide supplier. We also requested the ecological report, which Wessex Water said was recommending additional bat and bird boxes be erected on site, to encourage more predators of the flies to the site. A group of residents in Innox Hill (led by Jo) has also designed and erected a number of swift boxes on their properties, to encourage more birds to live here (although Wessex Water declined to sponsor these).

Some questions remain unanswered, including how residents could apply for compensation (for any costs incurred battling flies, and for nuisance suffered), and what more can be done if the netting is not effective. I hope it is, but if flies continue to be a nuisance, further action will be needed, and the survey results show that there could be enough people affected badly enough to be able to take legal action to abate the nuisance if required.

We will now need to communicate the survey results with residents, Wessex Water, MDC and FTC, discuss potential ways forward with local residents and gather people for the post-review meeting in June/July.

Fly Management Plan and Review of fly removal techniques:

Wessex Water acknowledge that large numbers of flies originate from the open trickle (percolating) filter beds at their Frome sewage treatment works at Welshmill. Their Frome Water Recycling Centre Fly Management Plan (May 2021, v8) set out their analysis of the problem, and their ‘good housekeeping’, and ‘best practice’ mitigation measures that are to be employed at the site: dosing with chemical larvicide, insectocutors, biological control, and insecticide spraying. It also recommends ways to reduce fly levels at customers’ properties, including closing windows and doors and fitting fly screens.

Wessex Water have also supplied the report they commissioned from Isle Utilities to review available techniques to prevent fly nuisance in sewage treatment works that use filter beds (Isle Utilities (2019) Fly removal techniques in filter beds to prevent fly nuisance complaints). The report concluded:

‘Isle conducted a comprehensive review of the existing and emerging techniques and solutions to fly
management within and outside of the water sector. This comprised the identification of solutions
from the Isle technology database and open source literature, a review of available research
projects, and interviews with relevant water utilities across the globe. Alternative techniques to those employed by Wessex Water were identified, but these were either not approved for use in the UK, were not available on the market here, or were not yet proven to be effective. The key finding from this review was that there are currently no viable alternatives to the methods used by Wessex Water to control flies in filter beds. It can thus be stated that Wessex Water are using the best available techniques.’

The report also noted that for alternative solutions to be employed, further research would be required into an alternative larvicide or with a university on a novel approach. However, the study did not look into the feasibility of alternative sewage treatment processes or relocation of the works, as ways of reducing fly nuisance, which were discussed briefly at the February meeting – and if the netting is not effective, these may need to be considered seriously.

Things you can do to help:

Until the results of the netting trial are known and discussed at the meeting, there are things residents can do:

1. Keep a record of any fly nuisance you experience at home, perhaps using the table below (provided by local resident Sally), and take photos and videos on any bad days. This is all useful evidence if it is needed at a later date.

2. Contact both Wessex Water on 0345 600 4 6000 and Mendip District Council on 0300 303 8588 (option 4, then 4 then 2) or email if and when flies are bad in and around your home, so they know and can respond too.

3. Keep in touch and let us know how the flies are by emailing

4. Please let me know if you would like to attend the review meeting in June, and a residents’ meeting before that.

Example table to record fly nuisance:

x/x/xxRede.g. Swarm outside, cannot use garden. Flies in kitchen, in bedroom at night
x/x/xxAmbere.g. Slightly less bad but still lots of flies today.
x/x/xxGreene.g. Very few today – can open windows and enjoy garden at last.

I hope this all helps,

Adam Boyden

Lib Dem Mendip District Councillor for Frome College ward, and Somerset County Council candidate for Frome North division

Published and promoted by Grahame Baker on behalf of Adam Boyden (Somerton & Frome Liberal Democrats), all at 5 Church Street, Yeovil BA20 1HB.

The Liberal Democrats will use any personal data we collect in accordance with our privacy policy at: To exercise your legal data rights, please email:

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