Liability for water damage

woodpecker

A main sewer belonging to Thames Water runs through our back garden. It is listed on the deed to the property, and when we bought the house one of the conditions of the freehold is that we allow Thames water access to the main for maintenance etc.
We have had three cases of the foul drain in our garden overflowing during the past two years. Each time the subcontractor comes out and confirms that the blockage is not on our side, and they fix the problem for no charge.
The problem is, this is sewage going into our garden. We have a fishpond nearby, and if the flow goes into it, everything is likely to die, not to mention the hygiene issue of having excrement etc across our pathways, flowerbeds etc.
We also have three kids, and I'm concerned about the health risk.
It doesn't cost us anything financially, but I'm also getting fed up with having to call out engineers, stay at home to give them access, and have a terrible smell throughout the house (the kitchen and bathroom water starts to back up when the sewer floods) every time this happens.
Do we have any kind of case against Thames water to make them sort this problem out once and for all, or to claim compensation for the damage to our garden?
Any advice gratefully received!

Joan_Doe

I have a similar problem, but can't see a link to make a new post so am replying to this old post.