Post by Tim StreaterSomething I'm trying to understand is the extent to which the water companies
have much control over the sewage dumping business. We know, or we ought to
know, that there's only one set of pipes in some? most? all? areas [2] which
act as sewage pipes but also as storm drains [1]. If you get a sudden huge
downpour then this system can be overwhelmed and they have to dump the
contents. Now, how many of the public know this? None? Some? All? The way it's
all reported you could easily get the impression that the water companies are
just doing it for fun.
Can anyone shed any light on this?
IANA drainage engineer but AIUI it's because they haven't been investing in
infrastructure, ie building new treatment plants. A new housing estate gets
built, NNNN new houses discharge into the same sewerage network as before.
All of a sudden the sewage works is 'overwhelmed' when it wasn't before.
Also increasingly heavy rainfall from climate change is stressing the system
more than it previously was. Again the water companies should have been
building to cope with that, but they haven't. This is why there can be
localised flooding far away from any rivers etc - the water backs up in the
sewers and then spills out into houses.
It's also possible some treatment plants are closed / offline / reduced
capacity due to lack of investment. I've heard of some specific plants
being closed, but don't have a good insight into whether that would impact
network capacity.
But if you try to get Thames Water to actually do something when you have a
sewerage issue, it's months and months of hassling them and repeatedly
missed deadlines. It's almost as if they just want to do the minimum and
fob you off so they don't have to spend money on their network.
Basically what was the ultimate fallback in case of an extremely rare event
is now used routinely, and the water companies reckoned that was cheaper
than building something to handle it.
Post by Tim Streater[1] Also worth noting is that the decision to do this was taken in Victorian
times when it may have seemed a reasonable cost savings measure.
[2] I'm told that in Whitstable the storm drains are largely separate from the
sewage system. Is this common or uncommon?
There are street storm drains, and rainwater drains from private gutters.
It's common to have separate storm and foul water drains on new builds in
some areas, but they're combined in older areas. Some properties have
soakaways, but many drain into the foul water system. On clay soils
soakaways are of limited use when the ground is waterlogged, so that
typically drains into the foul water system.
That means it has to take the rainwater load from the NNNN new houses and
drives, streets, etc as well as their bathroom waste, which makes a lot more
pressure on the system.
It's common to have sustainable drainage systems, ie a foetid pond in the
corner of the development, to reduce rainfall load. But it doesn't work so
well in urban settings where the site isn't big enough.
Theo