How do drains work?

John Clark writes…

First published:  August 2007 – Gazette & Herald

Nearly twenty years ago, my son, Alasdair, asked me ‘How do drains work?’ I cannot remember my answer to him but the truth is ‘I don’t know’. I know some basics like: the water runs off the roof or the roads, down the drain and ends up in the sea. It’s the bits in between I don’t understand.

Nearly thirty years ago there was a great fuss because vegetables grown in the Thames Valley contained high levels of heavy metals like Mercury and Cadmium.

How had these rare metals got into our food? We were told they came from the sewage used for growing the vegetables. Some of us found it hard to believe that human excrement contained high levels of mercury, zinc and cadmium. What diet would you need to be on to produce this? ‘Ah, well it’s not like that’ came the reply. The sewers run past the ‘Trading Estate’ where they gain these heavy metals. Why did we allow valuable heavy metals to become mixed in with the sewage?

There is yet another problem. When there is flooding, the flood water contains sewage. At this point we have achieved the ultimate in what we don’t want. Wasted water, wasted sewage and wasted heavy metals all washing down the street or, even worse, in peoples houses. Surely we can do better than this.

There are therefore two problems with flooding.

Water mixed with metals and sewage
Too much water in too short a period of time
Sewage must stay as sewage so that it can be used as a fertiliser. Thus reducing fossil fuels and energy presently used to make chemical fertiliser.

Oils, metals or other materials must not go down the drain. Water from industrial estates should be isolated from the rest, and treated separately.

Now comes the question of surface water, drains and flash flooding. This water must be handled separately in a more controlled way than just allowing it to flow as and when. When we talk about droughts, the solution is to save rain water in water butts. Why does the reverse not apply to heavy rainfall? Well before heavy rainfall is forecast, why do the ‘agencies’ not call upon householders, schools, hospitals etc. to release water. If each household in the UK stored 1,000 gallons, this could be used in times of drought. Equally, it could be used to store 25 billion gallons of water that would have gone into the flood.

Before I am deafened by the cries of ‘cost’ can we consider the ‘cost’ of sewage floating around the kitchen. Equally, what is the cost of houses without water or electricity? If the above concept works, why does it need to be limited to housing? Could the water off our main roads, car parks, motorways, airports all be stored alongside? It could then be stored or released so as to reduce the potential flooding or drought.

The Romans didn’t know how water in pipes worked. Thus aqueducts only and no upstairs bathroom.  I don’t know how drains work but I’m sure we can do better than Victorian sewers and drainage systems.