Not exactly DIY but should anyone happen to know. In coastal areas the road gully drain system seems to be outputted to the sea via flap-valve outlets. Assuming no breakages in the system is there any reason for that road-gully system to be also connected to residential sewer system? I'm aware that house-roof rainwater downpipes may be connected to the sewer system or to soak-aways.
Flap valve outlets tend to be used where flooding is likely. Most domestic rainwater systems don't need them.
The issue is the volume of water in a flash storm and where the local treatment place can cope. Best to keep them separate.
AIUI the usual practice is to keep storm water and sewage separate, but in many places they are combined, for example, in parts of Cornwall, but I don't know how widespread it is elsewhere. This can lead to problems at periods of very high rainfall when the sewage system can't cope, and overflows into local rivers by design, carrying with it raw untreated sewage which then ends up on beaches etc. Not nice if you put your foot on a turd on the beach, or meet one floating in front of you face while swimming.
From a recent CCTV survey, the gully system is only 100mm pipe so I doubt it can cope with a cloudburst. The outlets to sea are 300mm diameter though. As far as it goes, no apparent interconnect to the domestic system, for anyone interested , CCTV survey and plans etc off
Interesting - combined sewers is not a term I'd come across. It looks as though the tell-tale of a combined system outfall is condoms, sanitry towels etc coming out of the outfalls. No one has ever reported seeing such foul sewer stuff lingering at the local outfalls after a sea storm surge or a cloudburst over the local roads. So presumably good news there. Just as well as the nearest local sea outfall flap is jammed open a cm or 2 at the moment
Dumping surface water straight into the sea, via flap valves, is quite common in coastal areas, even if there is no risk of flooding.
For at least half a century, all new builds have had separate storm drains and foul sewers - although they are still combined on older properties.
My belief is that the practice of dumping raw sewage straight into the sea has long been discontinued - so anything going in to the sea now should only be storm water.
Yep and if connected to the foul water system the water company may well be charging you for the privalidge. Not sure how many hoops you'd need to jump through if you altered the drainage so surface water went to a soak away.
I think you mean "as a matter of course". There is still discharge of raw sewage when combined systems can't cope with rainfall. That's why eg Thames Water want to spend a bob or 2 on the Thames Tideway Tunnel
unless there is an excess of rainwater caused by a storm which causes a sewage works to overflow.
Well it depends. I seem to recall many moons ago when Bognor decided to use a proper sewage plant, lots of drains needed to be rerouted but the roads were still left feeding into the sea. Its been a long while since then of course, but hopefully this is the way its now done in most places where the pipe is terminated just off shore.
Brian
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