Concerns have been expressed by East Kennett residents over sewage flowing into the River Kennet.
Recent wet weather has caused a high water table and as a result pressure on the sewers is pushing manhole covers up.
Charity Action for River Kennet (ARK) is concerned that sewage leaking into the river is becoming a problem.
Charlotte Hitchmough, director of ARK, said: “Sewers leaking into the river are cause for concern.
"We’ve had reports of sewage leaking into the river in other areas including Coopers Meadow, Stonebridge and Aldbourne, so if anyone does spot anything they should report it.
“The first port of call should be the Environment Agency but if they let ARK know then we can put a dot on the map along with evidence and can present a stronger case to Thames Water.”
The issue in East Kennett was first bought to the attention of town clerk David Snape in December who reported it to the Environment Agency and Thames Water.
He said: “When residents alerted me to the situation I contacted Thames Water which responded to the problem within 24 hours and has been proactive in managing the situation since then.
“I have also been in contact with the Environment Agency and monitor the river myself on a daily basis.”
Thames Water has had two tankers pumping out the sewers at the pumping station, seven days a week, and has now said a third will be brought in to tackle the problem.
A spokesman for Thames Water said: “After the wettest year on record the ground is like a soaked sponge, so flood water is continuing to run into our sewers, which are designed to take waste water, not groundwater and flooding too.
“While our network and pumping station in East Kennett have been working as they should, they have been struggling with the sheer volume of water.
“We have been tankering away excess flows of waste water to protect the environment and will continue to do this until the water infiltrating our network subsides.”
The Environment Agency is monitoring the situation carefully but so far has found no signs of pollution.
A spokesman for the agency said: “We are aware of the incident and we are in ongoing discussions with the water company about the best way to alleviate the problem.”
Anyone who spots a sewage leak can call the Environment Agency on 0800 807 060 or email ARK on pollution@ riverkennet.org