is our hot water safe

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8 years 9 months ago #509754 by Ruth
Replied by Ruth on topic is our hot water safe
When I was a telephone technician, the weekly duties roster would include a regular turn at battery bank maintenance (in the Mt Albert Exchange a huge room of two batteries like small lap-pools with each cell requiring its acid's specific gravity to be read) and on that same duty round was the air conditioning cooling tower, which involved climbing up into the attic somewhere. I can't remember what we had to do, but I am pretty sure it included the pouring in of something which was to stop Legionnaire's being able to develop. Whenever an air-conditioning-related outbreak turns up in the news, I wonder who hasn't been doing that part of their job properly!

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8 years 9 months ago #509755 by spark
Replied by spark on topic is our hot water safe
Hi,

I believe that G12 of the building code is relevant:
www.building.govt.nz/UserFiles/File/Publ...tion-amendment-9.pdf

See clause 6.14.3 (page 39 of the PDF):
6.14.3 legionella bacteria
Irrespective of whether a mixing device is installed, the storage water heater control
thermostat shall be set at a temperature of not less than 60°C to prevent the growth of Legionella bacteria.

Clause 3.5 (page 52) also states:
3.5 protection from legionella bacteria

3.5.1
To prevent the growth of Legionella bacteria, solar water heaters must either:
a)
have a continuously energised heating element fitted within 55% of the bottom of the water tank (by volume) and a thermostat set to 60°C or higher, or
b)
be controlled so that the water above the element is heated to 60°C once a day, and the element is in the bottom 20% of the water tank (by volume) and no more than 150 mm from the bottom of the tank, or
c)
be controlled so that all of the stored water is heated to 60°C or higher, once a week for not less than 1 hour. The temperature must be measured by a probe in the bottom 20% of the water tank (by volume) and no more than 150 mm from the bottom of the
water tank. For open loop systems the stored water includes the water in the solar collector and water must be circulated through the collector during the heating period.

COMMENT:
Paragraph 3.5 of this Acceptable Solution provides ways to demonstrate that the NZBC Clause G12.3.9 (i.e. “A hot water system must be capable of being controlled to prevent the growth of Legionella bacteria”) is satisfied. This is a heat disinfection method which is considered the most effective method to control Legionella.The heating required to control the growth of Legionella does not necessarily have to be achieved using supplementary electric heating; it could also be achieved using gas, solar or wood as a heating fuel.

Cheers

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8 years 9 months ago #509762 by 2D
Replied by 2D on topic is our hot water safe
Where we lived before here, we had solar water heating. We used to turn the electric element on overnight, so that we had got the max solar heating and then turn it off again in the morning, so that the solar heating could do its thing again. It worked well - in sunny times it used hardly any electric topup but when it was rough weather we still had hot water in the morning for showers and such. Wish we had it now - we shall do so as soon as we can afford it again.

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