Recently amongst many other plumbing jobs I replaced the ball valves in the DW and FE tanks with new part 2 floats.
Both of the tanks were very unpleasant. The 50 gal DW tank was full of limescale/brown grit and other... I drained it down and cleaned the tank using an ice scraper and an old towel! Really tough job with a final bleaching of the tank! The FE tank was full of brown rust I presume. Didnt bother bleaching this just cleaned it. The state of these two tanks made me think that maybe this is something that should be done regularly, maybe annually. Is it worth it? Thinking about legionella and otherwise in vented systems. Am I worrying about nothing?
It does make sense to clean out the DHW tank periodically and to remove grit etc.
For the DHW feed tank, you should have a cover and ideally a water byelaw kit to connect the overflow, vent etc.
There are millions of tanks in use in the UK and people are not going down like ninepins with Legionella.
For the CH FE tank, sometimes there can be brownish gungy stuff arising from corrosion inhibitor etc. If it's rust, then perhaps you don't have inhibitor and should or there is pumping over in the system. There is no real need to clean jus tthe tank, but if there is rust and sludge then the CH system ought to be cleaned as a whole and inhibitor added.
IIRC, Legionella has to be vapourised into steam and inhaled to make it dangerous. Hence why most outbreaks occur through inadequate cleaning of industrial cooling towers.
On Dec 8, 12:07 pm, "Matthew" wrote: Thinking about legionella and
No.
More info here than you can shake a stick at;
formatting link
bacteria are common in the environment being found in lakes, rivers and reservoirs in small numbers. They are in the cold water mains supply, in small numbers.
Given favourable temperatures and a source of nutrients, they will colonise a water system. If the water is dispersed as an aerosol (showers, spray taps) it will be inhaled and will colonise your lungs. A lot of people contract it and recover without realising they had it; anyone with a compromised immune system will probably die unless treated.
Water temperatures in the range of 20 to 45 degC favour growth; blood temperature 37 degC ish is about ideal. Hot water should be stored at
60 degC and be 50 degC at any outlet within 60 seconds (commercial, should be much quicker for domestic). Cold water must be kept below 20 degC at all times.
The gunge, scale, rust and biofilms in the tank are a source of nutrients and provide a safe harbour for legionella, protecting it from high temperatures in the HWS system, that would otherwise kill it. The tank has got into that state because dirt can get in. Get a Bylaw 30 compliant tank (insulated, snap-on tight lid, screened overflow and air vent, etc..) and install and insulate it carefully. They will stay clean, save for deposits of limescale in the bottom of the tank which can be syphoned out every year or two. The tank should provide not more than 24 hours use, to prevent stagnation. Many water storage tanks in UK lofts are utterly disgraceful, I wouldn't wash my car in water from some I've seen.
The F&E tank shouldn't get hot and will get colonised by any bacteria. My one was filled with a jelly-like slime ( possibly psedonomas). The water shouldn't be used or become an aerosol, so shouldn't be a hazard. I've converted to a sealed system now.
On Dec 8, 12:07 pm, "Matthew" wrote: Thinking about legionella and
No.
More info here than you can shake a stick at;
formatting link
bacteria are common in the environment being found in lakes, rivers and reservoirs in small numbers. They are in the cold water mains supply, in small numbers.
Given favourable temperatures and a source of nutrients, they will colonise a water system. If the water is dispersed as an aerosol (showers, spray taps) it will be inhaled and will colonise your lungs. A lot of people contract it and recover without realising they had it; anyone with a compromised immune system will probably die unless treated.
Water temperatures in the range of 20 to 45 degC favour growth; blood temperature 37 degC ish is about ideal. Hot water should be stored at
60 degC and be 50 degC at any outlet within 60 seconds (commercial, should be much quicker for domestic). Cold water must be kept below 20 degC at all times.
The gunge, scale, rust and biofilms in the tank are a source of nutrients and provide a safe harbour for legionella, protecting it from high temperatures in the HWS system, that would otherwise kill it. The tank has got into that state because dirt can get in. Get a Bylaw 30 compliant tank (insulated, snap-on tight lid, screened overflow and air vent, etc..) and install and insulate it carefully. They will stay clean, save for deposits of limescale in the bottom of the tank which can be syphoned out every year or two. The tank should provide not more than 24 hours use, to prevent stagnation. Many water storage tanks in UK lofts are utterly disgraceful, I wouldn't wash my car in water from some I've seen.
The F&E tank shouldn't get hot and will get colonised by any bacteria. My one was filled with a jelly-like slime ( possibly psedonomas). The water shouldn't be used or become an aerosol, so shouldn't be a hazard. I've converted to a sealed system now.
If you're in a hard water area you can fit a Fernox bag-in-the-tank scale inhibitor. These are simply a mesh bag full of crystals of a phosphate salt which prevent scale deposition. The instructions say to hang them in the middle of the tank in free water, but most people hang them under the ballvalve. They need to be renewed every year or so, when the crystals have all dissolved away.
Legionella is a real risk. Most people do not realise they have legionella as it often manifests as cold/pnuemonia type symptoms and is put down to a virus/bacteria, from which most normal people recover. It can however kill.
Legionella is not spread by steam but is spread by breathing in aerosols, small water droplets which can get into the lungs. This makes it high risk in showers, particularly showers that are not used often, as it gets into the water stream and is broken up into the small droplets. The person showering is stood directly below the stream and breathes in the bacteria. Showers should be flushed at least weekly if not used regularly and the water should be as hot as possible whilst flushing to kill bacteria within the pipework.
Regulations in the UK for public use buildings state that the heads of showers that can harbour these bacteria should be cleaned and disinfected at least every 3 months.
Many hotels on the continent can be causes of legionairres disease in early season for this reason. Showers have been left with stagnant water in pipes until the new season at which point a holiday maker stands underneath and has a shower in nice bacterial soup. Always run the shower into a sealed bag and carefully place it down the drain if you are going on holiday early season in many holiday resorts.
Whilst what you say about 50=B0C killing the legionella bacteria is strictly true (it takes several minutes at this temperature) it is often the case that the entire cylinder does not reach 50=B0C. Heat rises and often there is a cold spot at the bottom of the cylinder in which the bacteria can grow. This is particularly prevelant on large cylinder and large calorifiers found in hospitals and the like.
The presence of biofilm/limescale and dirt as previously mentioned can cause additional problems of protection and nutrients, thus providing a breeding ground for legionella.
Cooling towers generate spray (and some stem if running hot) and are also nice nutrient rich, warm and pleasant areas for legionella to breed if left unchecked. Most cooling towers are very well managed through regulation and company policy and actually pose little risk to the public.
The F&E tanks should be examined for rust as other bacteria can also cause large rust pits that if left unchcked can rapidly cause pitting to such a degree that pin hole leaks can occurr. If rust is a large problem it may be best to clean and dry the tank and coat the tank with an epoxy sealer to protect the metal surfaces from the bacteria within the water.
While that is still accepted as a possible source of infection, it is now considered to be a minor one. Current thinking is that the primary method of infection, including that in the original outbreak, is aspiration of infected water and a high percentage of domestic stored water has been found to be infected. What makes it rare is that aspiration - inhaling water droplets from the mouth - is not common and that there are few occasions when stored water enters the mouth. The people at highest risk in the UK are, therefore, those with severe coughs, such as many smokers, and people who clean their teeth with stored water that comes from an unsealed cistern. Infection is carried into the stored water by insects and the point of the requirements of the Water Supply (Water Fittings) Regulations 1999, which replaced the Water Regulations, is to exclude them from stored water.
As others have said, there is a definite risk with open cisterns. Your domestic cold water supply cistern should have a tight-fitting, insect and light proof lid and be fitted with a Water Bye-Law kit. Although the Water Bye-Laws were superceded in 1999, the kits are still known by that name and will include an insect-proof screen for the warning (overflow) pipe, with a dip pipe that will take the end of the pipe just below the full water level, an insect-proof air vent, to allow air in and out as the water level changes and a tight-fitting seal for the hot water cylinder vent pipe.
Aspiration of infected water in the mouth is now considered to be the primary route of infection, although, obviously, that does not make showers any less of a risk, as they can be the source of that water.
Any idea if there is a low cost way of testing for high levels of Legionella or other risky water borne bacteria? I'm thinking of the scenario where there is an adult resident that frequently succumbs to cold and flu like symptoms and it would be nice to narrow down possible causes. I know it would be straightforward to disinfect the water system but it would be nice to track down causes rather than hitting and hoping.
In case it is of interest, the scenario is in a 4 storey multiple occupancy building with loft header tanks. Hot water vent pipes go all the way to the top so there is great scope for stagnant partially heated water in these pipes. Many residents have converted to combis so fewer are using the header tank water, leading to plenty of stagnant cold water too.
" Analysis of water for legionella should be carried out by a UKAS accredited laboratory which takes part in the PHLS Water Microbiology External Quality assessment Scheme for the isolation of Legionella from Water. The interpretatioin of any results should be carried out by an experienced microbiologist." ( from 'Legionnaires' Disease, The control of legionella bacteria in water systems', HSE).
A blood test would confirm whether the person has had the disease, or whatever else they may be suffering from.See GP.
The buildings' water systems and control regimes should be regularly inspected and monitored. If the hot isn't at 50 degC at any tap within
1 minute, or if the cold gets much above 20 degC, you have a problem.
| | |On Dec 9, 2:05 pm, fred wrote: |> Any idea if there is a low cost way of testing for high levels of Legionella or |> other risky water borne bacteria? I'm thinking of the scenario where there is |> an adult resident that frequently succumbs to cold and flu like symptoms |> and it would be nice to narrow down possible causes. I know it would be |> straightforward to disinfect the water system but it would be nice to track |> down causes rather than hitting and hoping. | |No. | |" Analysis of water for legionella should be carried out by a UKAS |accredited laboratory which takes part in the PHLS Water Microbiology |External Quality assessment Scheme for the isolation of Legionella from |Water. The interpretatioin of any results should be carried out by an |experienced microbiologist." | ( from 'Legionnaires' Disease, The control of legionella bacteria in |water systems', HSE). | |A blood test would confirm whether the person has had the disease, or |whatever else they may be suffering from.See GP.
GPs services and tests called for by them are *free* to everyone at the point of need. He/she may believe you if you ask.
|The buildings' water systems and control regimes should be regularly |inspected and monitored. If the hot isn't at 50 degC at any tap within |1 minute, or if the cold gets much above 20 degC, you have a problem.
Yes, a good idea & hopefully that particular bacterium should be detectable if specifically tested for but previous visits during general malaise where blood was taken and broadly tested have revealed nothing specific.
It's just the cold that is held centrally, hot is heated and stored locally and comes through quickly and hot. My concern is that the hot water vent pipe (for the ground floor) has a 60 odd foot head which must be predominantly stagnant. When a bath is drawn or a shower turned on there is a great flow (due to the high head) and I can't help feeling that some of the water will be drawn from the near stagnant vent which would present a risk. The lower part of the vent pipe will become warm but not above 50 and with the water only turning over under high flow conditions I could see it being a prime spot for breeding bacteria.
The loft tanks are a linked pair but one appears to provide most flow with the other tending to stagnate and gunge up. This thread has prompted me to take a look at them and look at running a disinfectant purge for the block.
With respect you are talking bollocks. The water has to be turned into droplets such as spray. That is why so many, but not all, cases of Legionella are related to cooling towers. They create water droplets. Google Legionella. It is endemic in all water supplies.
On Sat, 9 Dec 2006 11:12:02 -0000 someone who may be "nightjar" wrote this:-
That has always been the thinking.
Alarmist. Most water, domestic or otherwise, contains the bacteria at low concentrations, where it poses little danger. The danger is caused when the conditions for the things to multiply rapidly are present, especially when vulnerable groups are exposed to aerosols.
Legionella is not spread by steam but is spread by breathing in aerosols, small water droplets which can get into the lungs. This makes it high risk in showers, particularly showers that are not used often, as it gets into the water stream and is broken up into the small droplets. The person showering is stood directly below the stream and breathes in the bacteria. Showers should be flushed at least weekly if not used regularly and the water should be as hot as possible whilst flushing to kill bacteria within the pipework.
Regulations in the UK for public use buildings state that the heads of showers that can harbour these bacteria should be cleaned and disinfected at least every 3 months.
Many hotels on the continent can be causes of legionairres disease in early season for this reason. Showers have been left with stagnant water in pipes until the new season at which point a holiday maker stands underneath and has a shower in nice bacterial soup. Always run the shower into a sealed bag and carefully place it down the drain if you are going on holiday early season in many holiday resorts.
Whilst what you say about 50°C killing the legionella bacteria is strictly true (it takes several minutes at this temperature) it is often the case that the entire cylinder does not reach 50°C. Heat rises and often there is a cold spot at the bottom of the cylinder in which the bacteria can grow. This is particularly prevelant on large cylinder and large calorifiers found in hospitals and the like.
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