Sorry Tim, I have only just seen this due to being on scout camp this weekend and therefore I was in bed by 9pm last night!!
With regards to your questions, most water treatment woks try to run at the same flow of water each hour, known as steady state operation' this is because each time the flow changes the settings for the dosing pumps adding each of the chemicals need to change to keep the right proportions and changing these can lead to issues. However the demand for water changes from hour to hour so there are a number of buried tanks in the network that fill when demand is less than production and drain when demand exceeds production. The added benefit of this is there is a store of potable water in the network for when there are minor issues such as bursts or interruptions in production. The service reservoirs will often hold between 12 and 24 hours demand. The issue comes when a supply area is reliant on one treatment works, either as the only source or as such a major source there will be a big shortfall if it stops. In these cases the water company is on a ticking clock to get the works back on before the water runs out.
As for you getting water when others are not, your supply will be from one of a number of service reservoirs supplied by Hardham WTW, but it will have other sources. The combination of the ratio of the sources (Hardham WTW vs Others) and the size of the reservoir compared to the demand will mean that different supply areas ran dry at different rates. It is possible that Hardham WTW may have been expanded over time resulting in different disinfection tanks for different outlets, and only one off these tripped and went off, or that one outlet may be supported by a bulk supply for elsewhere. The issue is once the disinfection process trips then either you treat a lot of water in the upstream processes and spill it to overflow or stop the whole site while you fix what went wrong and dump the water you no longer trust. The other issue is that restarting a WTW is not easy, which tanks have to be drained?, where does this water go?, once drained how quickly can you restart and refill them?, what flow do you start up at (it will not be max flow) and then how quickly can you ramp up to max?
Finally if the service reservoirs have run dry then how much time is needed to refill them and the pipes in the ground? remember that when water returns everyone will flush their toilets, run the washing machines etc. and therefore the demand will be much higher and there is less excess production to fill the reservoirs.
The water companies may list their service reservoirs in some of their investment documents but only where they plan to invest, they may also list them if you look up the WQ sampling they have to publish as the reservoir will be a key sampling location. However as observed by Pingu there is a paranoia regarding contamination so the sites tend to be well fenced, monitored and the access covers tightly secured and alarmed. Someone who knows what they are looking for can spot them on google maps satellite images, but it can be a bit of a needle in a haystack search.
It has always struck me that the Lea Valley reservoirs and water processing plant are a tad vulnerable to being tampered with, say, by drone - no matter how much anti-ram, anti-climb fencing, infra red detection beams and cameras are put up around them, particularly given the amount of open land around them.
Or maybe that's just what goes on inside my head.
Jurek, Both the Lea and Thames reservoir trains are raw water (untreated) and feed into the WTWs there will be monitoring before and after treatment. Unless someone manages to get all of the reservoirs at the same time there is redundancy as individual reservoirs are often unavailability due to algae blooms or other issues.
Is it that secret? If I walk up the hill I can see where my water is coming from as Thames Water has one main reservoir. I think the concern over how easy they are to access is unfounded; the local sailing club and fisherman both play in my water before I drink it. I suspect the sensitive areas are the treatment plants rather than the reservoirs.
People playing on the untreated water is one thing the treated water is another case entirely. These are stored in covered reservoirs like the one on this
map.
