Changes to Defra regulations by the Government will see Thames Water's sewer network increase by around 60% from 1 October 2011.
As a result of the legislation change, which aims to resolve ownership issues, sections of drains and sewers currently owned by six million London and the Thames Valley homeowners will transfer to Thames Water, which will be responsible for the upkeep of the systems.
This will increase Thames Water's network of sewers from 67,000km to around 107,000km, raising the 55,000 blockages a year the company currently deals with to 250,000.
Ahead of the move, Thames Valley has called on its customers to avoid 'sewer abuse' in a bid to limit the number of blockages it will have to deal with. It advises people not to dispose of waste such as oil, fat or other general waste such as nappies and sanitary products into the sewage system and bin it instead.
The disposable of fats down drains can lead to a build up of 'fatbergs', which block sewers and can in severe cases lead to sewage flooding.
Thames Water's chief flusher, Rob Smith warned the increase in the company's sewer network could lead to a "near fivefold increase in blockages".
Smith said: "It's really important people remember that just because certain sections of drainage are going to become water companies' responsibility from 1 October does not mean that we can mistreat our sewers by putting the wrong things down them.
"Sewer abuse can lead to other people's properties being sewer-flooded, which is a truly miserable experience and we are hell-bent on putting an end to it."
Defra estimates that the transfer of ownership will result in an annual increase to household's bills of between £4 and £14.
Links: Fat Mounds in London Sewers
My suspicion Alison, is that the chip pan fat and nappies have all been going down - with a lot of other stuff - but that the water companies had less incentive to raise this as a public issue, because they weren't called in as much as they now will be.
Why not? My guess is that a lot of stuff congealed and otherwise blocked up the system before it reached the water companies' pipes. So unblocking it was a problem to be solved - and paid for - by private owners, housing associations, local councils etc.
I hope that - if it hasn't already happened - there will now be urgent discussions between the companies and various public agencies about an effective publicity / public education campaign.
The change affects sections of sewer pipe or drain that are shared with another person's property or run through another person's land. The bit to the boundary of your land remains your responsibility unless it is shared.
Thanks for the link, Geoff. Following it I noticed that Thames Water's website has some very simple short videos illustrating both the problem and the effects of legal changes on different types of property. There's a direct link here.
I was also surprised to see - on the BBC website - (link by Site Admin) that "build-up of fat, caused by people pouring substances like cooking fat down the drain, causes flooding in 7,000 homes in the capital every year."
If you imagine backed-up sewage flooding your home or garden, that number seems more than enough to justify a bigger - but still cost effective - publicity campaign.
There's more information -in FAQ format - on the Consumer Council for Water website : www.ccwater.org.uk .