Bird Flu and Water Tanks in the Roof

"Martin Davies" writes: |> Markus Kuhn wrote: |> > Some types of bacterial eye infections are more prevalent in |> > Britain than in other countries. Our loft tanks are the prime suspects. |> > They are illegal in most other European countries, for obvious hygiene |> > reasons. |> |> Interesting. I've never even heard of anyone getting bacterial eye |> infections. |> |> Just how common is this bacterial eye infection problem, and is it known the |> exact cause?

Here is the full story on how your loft tank could make you go blind:

New Scientist, issue 2429, 10 January 2004, page 15:

WASHING your face while wearing contact lenses could increase your chances of getting a potentially blinding eye infection. And the risk is greatest in the UK, according to a leading eye specialist.

The culprit in question is a free-living, water-borne amoeba called Acanthamoeba, which can cause severe ulcerations of the cornea - a condition called Acanthamoeba keratitis. The disease is rare but extremely painful and can lead to blindness. "It's a ghastly disease," says John Dart, an ophthalmologist at Moorfields Eye Hospital in London. "It's very resistant to treatment and difficult to eradicate."

Contact lens wearers are most susceptible. Only around 1 in 30,000 contact lens users in the UK contracts the disease. But this rate is

To test the link, Dart and his colleagues analysed the mitochondrial DNA of Acanthamoeba found in eight patients and in their water supplies. In six of these cases the organisms were identical, indicating that the water supply was the source of the infection (Investigative Ophthalmology & Visual Science, vol 45, p 165).

Although some patients admitted to occasionally storing lenses in tap water or contaminating their contact lens cases with it, Dart believes the greatest risk comes from washing while wearing lenses or handling lenses with wet hands. He recommends that people keep tap water away from their eyes when they are wearing contact lenses."

tony sayer writes: |> >It's about time that our Victorian building regulations and British Standards |> >get updated to finally stop builders installing loft tanks that serve no other |> >purpose than to make fresh water to go stale and infectious before |> >it can be used in the bathroom. |>

|> Why do we still have them?. Is it 'agin the regs to connect the hot |> water directly to the mains incommer?...

I understand that loft tanks were required in Britain by the building regulations until the mid 1980s. Only then, the mains-pressurized systems commonly used in most of the rest of the world were finally permitted here to. No idea, why that wasn't allowed already 50 years earlier. If loft tanks are still being installed today, this is nothing but inertia. They seem to be a relict from the Victorian days when water pressure was only available for a few hours each day. Today, they serve no purpose other than to cause plumbing problems.

There still seem to be deeply rooted fears in Britain with regard to pressurised water. Why does the mains pressure in my street Cambridge rarely go above 1 bar? In other countries, the street pipe is at up to 10 bars, and a simple pressure-reduction valve at the water meter reduces that to about 4 bars inside the house, which is about right for a decent shower.

Markus

Have you complained to the Cambridge Water Co?....

Not really. About the only part that is likely to go wrong is the float valve and these are cheap to replace. They do have the advantage that they may well be able to deliver a greater flow rate than can be achieved from the main (in the UK at least).

Pressurised storage systems have pressure relief and safety valves and should be maintained annually.

Combination boilers have their own potential set of issues with heat exchangers and internal controls.

All of the options have their potential problems.

Two possible reasons:

- Because it was installed a long time ago and if the pressure were higher, there would be excessive leakage from the failing pipes.

- Because your supply is fed from a reservoir or water tower of limited height relative to your location.

That is interesting.

The advantages of the traditional UK system are that it requires only a relatively low constant mains flow rate (fewer sudden surges as with the electricity during TV commercial breaks). Also it is fairly immune from mains contamination. I think that is the main reason why it was kept until 1987 (?). Other countries with mains-only systems usually have a history of mains contamination which has necessitated a system of licensing plumbers and approval of water installations. One day there will be a mass poisoning incident and laws will be changed.

Secondly, there are storage cisterns and storage cisterns. The current plastic bylaw 30 compliant tanks, if competently installed and with a turn-over every 24 hours, will stay clean and the water will remain wholesome. I drink the water from my tank; it is clean.

However, some of the old water storage tanks I have seen were truly filthy; no lids, discarded lids, asbestos sheet lids, rotting leaves, rotting timber, animal remains, insects, rust, GF insulation, dirt, lead pipes, contamination with CH inhibitors, direct connection to the CH, Victorian lead sheet tanks constructed within a teak box, etc, etc.. These are a health hazard.

The pressure is low-ish (bar) so that the leaky old system doesn't waste so much water. I don't know where this post came from, so I haven't set FUs.

Both my grandparents houses, and my parents houses (built around 1910 and 1930) had mains pressure cold throughout from the start (all three properties in Wigan). So if it ever was rules rather than local practice - which I'm dubious about - there was a strong local component to the rules.

Considering how much water the companies already lose through leaks, I can see why they don't want to raise their supply pressure.

On Sun, 27 Nov 2005 22:21:58 GMT someone who may be Martin McGowan wrote this:-

That rather depends on what temperature the water in the hot water cylinder is elevated to and the risk is much the same whether the cylinder is fed from the mains or from a storage tank.

I'm sure bleach manufacturers claim so.

That is likely to increase the risk of harming humans, due to the bleach.

Incorrect. Long before the next yearly clean the little nasties will be around. However, as long as they remain in small concentrations then they are no problem. They only become a problem when they rapidly multiply at certain temperatures.

On 28 Nov 2005 18:02:22 GMT someone who may be n05W48+ snipped-for-privacy@cl.cam.ac.uk (Markus Kuhn) wrote this:-

An elementary mistake. The author may have spoken to an ophthalmologist, but neither appears to understand plumbing.

The water in a cold tank is not stagnant. Provided it is designed and installed properly such a tank is no great risk to health. It has the advantage of preventing back-siphonage, which can cause the supply to other premises to be infected.

I have no hesitation in drinking the water from the cold tank in my house. It is properly designed and installed.

There is nothing wrong with using lead tanks as long as the water is the right pH. The Roman empire wasn't plumbed with plastic pipe.

The risk of multiplication in mains water is so tiny as to be non existent due to the chlorine in the supply and the fact that it does not hang around to allow bugs to grow

So do the H&SE anywhere that supplies equipment that produces aerosols must be kept clean. that is why there is such a fuss about the water storage ponds on the cooling towers of air conditioning units. The problem with storage tanks is that a lot of the chlorine comes out of solution when the water splashes into the tank along with the slower diffusion from the stored water.

The bleach is flushed out of the system, but the amounts needed are actually very small. If I recall correctly we used about one litre in a

wrong the system will be clean and in fact the 2 intermediate tests each year proved that it stayed clean. I had no intention of getting into the position that a facilities manager did this year when she was in court on manslaughter charges when a couple of people were contaminated by the exhaust plume from her buildings airco.

The little nasties multiply very nicely at a comfortable showering temperature

Martin McGowan

David Hansen wrote: snip

The water tanks in the hostel where I was the maintenance engineer had GRP lids fitted to them with bolt on man hole covers to allow me to get inside for servicing and cleaning, each year i had to remove about one inch of sediment which was brought in by the water from the mains supply. It was that sediment which brought in most of the bugs. British mains water is unfortunately not always as clean as it might be. My niece was allergic to the coliform bacteria in her local supply, it wasn't a dangerous level in fresh mains water but in the storage tanks in her home, which were larger than normal they built up into a sizeable colony. her siblings were not affected and when she returned to the area after a number of years away she was no longer affected.

The design of water tanks to avoid any possibility of stagnation in areas of the tank is both an art and a science. In a square or rectangular tank it is very easy to have water stagnate in the corners and bottom 2 inches of the tank especially if the supply and outlet pipes are in the same face of the tank. If you have two joined tanks to give added storage capacity then the tank without the ball valve will certainly have a large measure of stagnant water. To get a tank with no stratification is very rare In a test the only set up which was garenteed not to stratify and thus stagnate was a round tank which was fed via an angled pipe which went down the side of the tank, thus causing the water to swirl into a vortex, the water was cut off manually. it was a test rig but could probably be replicated with a light beam and infra red cell plus an electric globe valve. A ball valve could not be used as in hard water areas you get a lime scale build up around the nozzle which can provide a home for bacteria, a torbeck valve might have been modified but the outlet tube is flexible so it cannot back syphon and would be difficult to hold at the required angle.

I always hesitated to drink water from cold tanks and mine were regularly sterilised. I no longer have that problem. I don't have any storage tanks. My last house did have the tanks and very grateful i was when we had power cuts as our local reservoir and pumping station always failed when the electricity failed and that was about 5 times a year. Martin Mcgowan

Don't use that, use ordinary "thin" bleach *if you really need to*, and ensure the system is cleaned out properly before/afterwards.

My parent's house in Aberdeen built in the '30s had mains pressure cold water everywhere too.

This should be qualified to read 'soft contact lenses'. And since these can absorb all sorts of things best to remove them before washing in anything.

Only if they are totally stupid.

Poisoning animals in the wild is how you get infestations - not remove them.

On Mon, 28 Nov 2005 23:08:02 GMT someone who may be Martin McGowan wrote this:-

Incorrect. A test will demonstrate that they are in low concentrations, at which they are not a great danger to health.

You are confusing procedures in large commercial/industrial buildings with houses.

Indeed. However it is a combination of temperature and time that allows them to multiply to dangerous levels. Provided that the shower is designed properly, either mixing hot and cold water at the point of use or raising water to showering temperature and then supplying it immediately, the risk to health is minimal.

There is concern over what is left in the pipe after the shower is turned off, hence some electric showers will drain this or run cold for a short while. One may debate whether this is overdoing things or a sensible precaution.

On Mon, 28 Nov 2005 23:37:43 GMT someone who may be Martin McGowan wrote this:-

Which is why sterlising water tanks does not remove bugs, as some people think.

Then the tank was not designed and installed properly.

Then the tank was not designed and installed properly. Having supply and outlet pipes on opposite sides has been taught for at least two decades.

Why not use Milton,s steriliser? a neighbour was advised by a water engineer that the well in the middle of her kitchen was OK to supply drinking water if she put Milton in it every now and again (once a year IIRC)