Burst of high pressure from hot taps & dripping exterior pipe

[bernardgreen]

where it has been pasteurised by heat and stored hot.

A simple cylinder does not pasteurise the water in it. A basic guide to the pasteurisation process ( power point )

www.foodafactoflife.org.uk/attachments/655ff1ea-a545-44f4fcd59aa1.ppt

 

[bernardgreen]

Oh please do tell us more about how bacteria can grow in water stored at 60°C

Is the water constantly at 60°C ? Or does it cool down. is the water at the bottom of the tank also at 60°C ? Could there be a zone of water at a nice comfortable breeding temperature. Maybe the bacteria that reproduce in the warm zone are killed when they are moved up the cylinder to the 60°C zone. But dead bacteria can be harmful ( allergic reaction ) and some bacteria produce toxins that are not neutralised at 60°C

EDIT

WRAS note that the whole cylinder should be heated to 60°C

If the pre-heated water is stored at temperatures between 20oC and 45oC, which favours the growth of the Legionella bacteria, and large numbers of the bacteria develop, measures may be required to prevent these bacteria causing harm to health. The technical guidance to the HSE Approved Code of Practice (L8) “The control of Legionella bacteria in water systems”, for the management of hot water systems in non-domestic premises, recommends for hot water storage cylinders that the whole contents should be heated to 60oC for one hour each day to prevent growth of Legionella bacteria in the cooler water at the bottom of the cylinder. Briefly raising the water temperature to 60oC is not considered effective.

from https://www.wras.co.uk/downloads/public_area/.../preheated_water_Nov_2014.pdf/

Legionella is only one of several bio-hazards that can develop in water

 

[JohnD]

a definition from your ppt

"batch pasteurisation – where the product is held in a specific temperature range for a long time, e.g. 62º C – 36º C for 30-35 minutes"

Explain why you think a HW cylinder cannot do this.

 

[bernardgreen]

Explain why you think a HW cylinder cannot do this

It could if the water in the bottom of the cylinder was held at 60°C for the necessary time ( WRAS recommend one hour for domestic pre-heated water ).

Any hot water taken from the cylinder will be replaced by cold water most often fed in at or near the base of the cylinder. This will take that area of the cylinder below 60°C and maybe into the breeding temperature for bacteria.

Batch pasteurising requires the batch to be held as a batch for the duration. Stirring of the liquid to reduce thermal stratification is used in a lot of batch processing.

 

[Dan Robinson]

Jesus it's unbelievable.

 

[JamesK]

An update. The plumber came round earlier and regenerated the air gap. As a result the pipe is no longer dripping, and the initial higher pressure on the taps is no longer there. He warned me the situation was likely to return unless I dealt with the shower mixer issue.

I think I will get advice elsewhere on this, and all of the above issues raised with the installation.

I appreciate everyone taking the time to advise...

 

[JamesK]

Out of curiosity... Is the mixer shower likely to be anything to do with this? I just can't get my ahead around this being a cause.

 

[muggles]

Unlikely - it would drip continually rather than intermittently if your shower was at fault

 

[Steelmasons]

It could if the water in the bottom of the cylinder was held at 60°C for the necessary time ( WRAS recommend one hour for domestic pre-heated water ).

Any hot water taken from the cylinder will be replaced by cold water most often fed in at or near the base of the cylinder. This will take that area of the cylinder below 60°C and maybe into the breeding temperature for bacteria.

Batch pasteurising requires the batch to be held as a batch for the duration. Stirring of the liquid to reduce thermal stratification is used in a lot of batch processing.

Hey Bernard , Google "de-strat pumps" (circulators)..
What are your thoughts with regard to CWSC's installed in loft space whereby the temperature of the stored water can reach in excess of 25/30c?....would it be an issue bearing in mind cold water outlets are also fed from these CWSC's??

 

[Newboy]

That one reason is that un-vented cylinders do not require a header tank and thus the risk of animals / rodents drowning in that tank does not exist with an un-vented cylinder.

Are you seriously suggesting that that is the only reason to install an un-vented system?!

 

[Steelmasons]

A simple cylinder does not pasteurise the water in it.

 

[bernardgreen]

Hey Bernard , Google "de-strat pumps" (circulators)..

Google not necessary, have experience of control systems for them.

...would it be an issue bearing in mind cold water outlets are also fed from these CWSC's??

It could be an issue if taps fed from the CWSC ( cold water storage cistern ) were considered as supplying drinking water. One reason CWSC are ( should be ) thermally insulated is to prevent the temperature of the stored water rising to far. Is there amy tmeperature control ( insulation ) on accumulators used to "supplement" low flow rate mains supplies ( a CWSC is in effect a large capacity accumulator but at lower operating pressure )

Potable water everywhere, silent operation, reduced pipework, better hot water performance etc are all benefits, amongst a few others you've been told several times

I accept these benefits can be achieved but the extra pipework required for the safety systems of an unvented cylinder may be more complex and critical than the simple rising main and descending feed and over flow pipes from the storage tank ( or cistern ).

 

[Madrab]

It could be an issue if taps fed from the CWSC ( cold water storage cistern ) were considered as supplying drinking water. One reason CWSC are ( should be ) thermally insulated is to prevent the temperature of the stored water rising to far.

Actually, properly designed, installed and used CWSC's are classed as containing wholesome water. That being that the water can be considered safe to drink.

https://www.wras.co.uk/downloads/pu...ote__cold_water_service_storage_cisterns.pdf/