Hydraulic designers should be aware the BCA 2011 has some key changes namely the inclusion of part three the Plumbing Code of Australia. The following is an extract from a NSW Planning & Infrastructure circular.
This year sees the introduction of the National Construction Code (NCC) Series, comprising the Building Code of Australia (BCA) as Volume One and Two and the Plumbing Code of Australia (PCA) as Volume Three.
The NCC takes affect from 1 May 2011. However it should be noted that in NSW the PCA (Volume Three of the NCC) will not be referenced at this time. Further advice will be provided when NSW adopts the PCA.
What does this mean for Hydraulic designers in NSW? The New South Wales Code of Practice Plumbing and Drainage will be omitted sometime in the future. I will keep you posted.
Wednesday, 25 May 2011
Hot Water Dead Legs
When a hot tap is turned on unless the fixture was recently used there is a time lag for hot water to flow. This occurs when the water in the dead leg cools over time, the cool water must first discharge before hot water will reach the outlet.
The question often asked is "what time lag is acceptable" and "what is good design practice". Should it be 5 seconds, 10 seconds or is longer acceptable?
As shown in the table below, a 15mm pipe with varying dead leg lengths significantly impacts time lag.
Note: 15mm has been used as an example, the dead leg lengths nominated do not comply with AS3500 in all instances.
What can be concluded from this information? Are dead leg lengths restricted by new low flow tapware? Are hot water systems becoming more complex with longer circulating loops to reduce time lag?
The question often asked is "what time lag is acceptable" and "what is good design practice". Should it be 5 seconds, 10 seconds or is longer acceptable?
As shown in the table below, a 15mm pipe with varying dead leg lengths significantly impacts time lag.
Note: 15mm has been used as an example, the dead leg lengths nominated do not comply with AS3500 in all instances.
It seems reasonable to assume dead legs over 10m to a single fixture will push the envelope for end user satisfaction.
It should also be pointed out fixture flow rates have almost halved in recent times but the way we design hot water systems and the regulations controlling design parameters has not been amended.
Is it time for a change?
It should also be pointed out fixture flow rates have almost halved in recent times but the way we design hot water systems and the regulations controlling design parameters has not been amended.
Is it time for a change?
About bdhydraulics
Welcome to my blog - bdhydraulics.
I am a hydraulic design engineer residing in Sydney, Australia. I have an interest in broadening my knowledge through sharing some of my day to day experiences working in a design office and receiving feedback from other similar professionals.
I am a hydraulic design engineer residing in Sydney, Australia. I have an interest in broadening my knowledge through sharing some of my day to day experiences working in a design office and receiving feedback from other similar professionals.
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