This page for clarity's sake is called drinkingwaterleadpipes.blogspot.com/ and is done by a free page building/hosting service of googlemail.com to whom I tip my hat with respect and gratitude for the quality of this service.
There is a Blog comment response button near the bottom of the page that is saying the number of comments and my email is graysgrace@googlemail.com.
.
Most people don't even think about it and may have the poisonous metal Lead in their fat tissues and and the Brain cells fat tissues from their cold water tap and the Lead pipes in their Kitchen....
.
Early one morning after a nights sleep and feeling thirsty I poured myself a glass of drinking water from the Kitchen cold tap.
And thought through my half asleepness how much lead may have leached into the water from the drinking waters Lead pipes.
But then I remembered that I had just flushed the Toilet and so the pipes would have been flushed through.
Then I wondered, supposing I was staying in a friends big house where the Lead pipes are so long going to the Public water supply pipe.
Even flushing the Toilet may leave undesirable amounts of Lead in the water so making a large house of less interest on the market.
I worked out a typical cistern has 12 Litres amount of water based on the dimensions 16 cm * 45 cm * 17 cm deep of water in a typical '50's Toilet cistern which is a bigger flush than modern water saving cistern flushes.
A typical Lead water pipe has an internal bore of 20mm so at the most 12240cm^3/100*(3.14*2.2cm*2.2cm/2)=159 Metres length of Lead Pipe would be acceptable for a single Flush.
Or with a small 20 mm bore pipe of 29 cm long holds 80 Grams of water or 80 cm^3 volume of water.
0.29 Metres pipe for 0.08 Litres of water so 12 Litres/0.08 Litres=150 Metres long.
Most pipes would only be about 15 Metres but it still might make a house less desirable because of having to flush out at least 1.2 Litres every time you fill the kettle.
For a big house with a 50 Metre water pipe 4 Litres would need to be flushed each time.
The UK Government has a Drinking Water Inspectorate section and recommends a washing up basin of water should be flushed through and used for watering plants instead!
In its web site http://www.dwi.gov.uk/consumer/faq/lead.htm it says there are to ways Lead gets into the water.
One is by water standing in the pipe for a longish time and the other is if the pipe is disturbed by heavy vibration, and some lead oxidation rust powder may become dislodged and settle in the pipe waiting to be moved through when the water is next called for.
The DWI (Dep't of Water Inspection) web site says that the water supplying company is to supply free of charge a replacement plastic pipe for any Lead part of their pipe from the mains public water system through to either the boundary of the property or its water meter.
Whichever is the shortest probably.
.
To sell the service of replacing the lead pipes I think first to find the Lead hurt or sensitive groups of people.
Also to ask for a lead test from Thames Water for my Mums house.
Maybe an Advert for those with the lead pipes of a big house.
There is also the Gardening, Building and insurance challenges of the work of changing the pipes. Amazingly somtimes Lead Poisoning is called Plumbism!
"A source of exposure to lead can come from drinking water. This is of particular concern internationally in cities where lead plumbing is still being used. In Australia a problem arises when rain water from roof runoff into tanks is used as potable water. If there is lead contaminates in the roof area or storage tank, the rain water will contain lead. The Australian Drinking Water Guidelines allow a maximum of .01 mg/dL lead in water."
http://en.wikipedia.org/wiki/Lead_poisoning
.
There is many little problems to overcome when changing the pipes and if it was my house I would want to change the internal pipes that are meant for washing aswell.
The trench needed to change the mains pipe in the ground can scar a garden but there is a tunneling machine that can save alot of that.
The alternative seems via cheap labour digging with shovels and watching to not damage other pipes and cables and place garden parts ready for putting back.
Thames would reconnect for free at their end of the new blue plastic pipe in the ground and a conscientious of internal decor plumber at the other end.