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Discuss Legionella risk of expansion pipe to water tank in the Plumbing Jobs | The Job-board area at PlumbersForums.net

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MOSSEP

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Plumber
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Hi, been asked to do a job which seems a little strange.

Large office building in London, expansion pipe to roof mounted cold water taken has broken off leaving a hole in the tank, this was noticed when the annual legionella risk carried was out and they have said that the hole needs to be filled up. I said thats easy enough, I will fix the pipe and put it back into the top of the tank so its back as it was. They said no, its a legionella risk having it back in there and they should have another tank fitted for the pipe to go into that then discharges into a gutter, and they will fill the hole. The client is worried about the legionella risk so just wants to do what they have requested, so, is there a risk involved if I just repipe it as it originally was?

Martin
 
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Sorry, might be me but are you talking about the feed and expansion pipe in the bottom of the tank or the vent pipe through the lid ?
 
You got it, the vent pipe that used to go into the lid. Thats why Im a bit puzzled as so why they say it will cause problems?

Assuming it doesn't go back in, other that a waste of water when it vents, is there any reason why it cant go into the gutter?
 
Legionella says otherwise, do as your client ask get them to sign that that's how they want it. This will rumble on until the cows come home. In theory L8 is right, but thats not how we do it. Makes no sense but I do see your dilemma. Best of luck.
 
I did say to the client that they should get the request in writing form the company that carried out the test.

Is there even any point to discharging it into a separate tank? It may as well go straight into the gutter if thats where the tank will empty when it fills.
 
Sorry stating the obvious, but - How do they figure out the vent pipe is risk of Legionella?
I guess they theory is the pipe is open to the atmosphere and the water inside it is heated to some extent. Storage tank water is exactly the same anyhow.
I would be careful about putting the vent to elsewhere where it could freeze or the hot water damage something. The end of vent pipe would need to be not too low or it would start a syphon and empty the cold tank.
 
Legonella risk assessments!! You can go on a course now for a few hundred quid and call yourself an expert. ( one day course!) the troubleis, they know nothing about plumbing installations.
The very small risk is outweighed by the risk of siphoning dirty stagnant water from the seperate cystern.
Apparently, one of the greatest risks for legionella, is the end of the spout on a hot tap!

All you can do is what they say I'm afraid.
 
Sorry stating the obvious, but - How do they figure out the vent pipe is risk of Legionella?
I guess they theory is the pipe is open to the atmosphere and the water inside it is heated to some extent. Storage tank water is exactly the same anyhow.
I would be careful about putting the vent to elsewhere where it could freeze or the hot water damage something. The end of vent pipe would need to be not too low or it would start a syphon and empty the cold tank.

Probably through a build up of scale on the end of the pipe.

Worries me that people are willing to ignore the water regs to try to minimise an already low risk situation. ...
 
Id be worried if it was rerouted elsewhere to discharge over a gutter or empty tank that someone in the future may come along, see an open end and cap it off.
 
All sounds like ball cocks to me.
The risk from a vent pipe is aerosol/airborne spores ( eg in water vapour), Legionnaires disease is contracted by breathing in those spores.

The vent pipe is best put back through the sealed lid where it belongs.

Whether it vents over the existing tank or a separate one, it still vents.




In my opinion.
 
obey building regs and water regs. so feed n expansion back into tank. then all that is required is for the owners to have annual check, system clorination if need be and get them to ensure high risk areas dealt with, ie any shower heads, or places where water can mist, hence why watercooled roof top air con units are so at risk of legionaire build up.
 
I thought it was to do with the fact that warm water in turn could warm up the cistern. That in turn would increase the risk of legionella. Have never come across this. Have come across faulty boiler stat, faulty cylinder stat, hot water forcing it's way up cwds. Vent was damaged in loft boxes placed on it!
 
I thought it was to do with the fact that warm water in turn could warm up the cistern. That in turn would increase the risk of legionella. Have never come across this. Have come across faulty boiler stat, faulty cylinder stat, hot water forcing it's way up cwds. Vent was damaged in loft boxes placed on it!

No, that's another fault.
If your installation be it heating or hot water is correct, there should be no water coming out of the vent pipe, it is there to release gasses.
The cold feed pipe is designed as feed and expansion. It allows water to fill the system and expanding water to move into the tank.
The vent pipe also helps to ensure that the system is at atmospheric pressure at all times (open vented), on occasion water may purge from the vent under certain circumstances, hence its position, over the tank that feeds the system it is designed to be venting.
 
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