Difference between Flush Rate and Flow Rate

Ziye Liu's picture
Ziye Liu
Architect
January 11, 2015

Hi, I'm a little confused about these two definitions. In the Indoor water blank template, I can understand that the water closet and urinals are belong to flush fixture and lavatory, shower and kitchen sink belong to flow fixture.

However, when I read Water Use Reduction Additional Guidance, in the DUAL FLUSH TOILET FLOW RATE Section, the Example Average flow rate is derived from flush rate, and it still asks for how the weighted average flush rate was derived at the end of that section.

Could you help me explain that? Thanks for your help.

Z

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Rob Freeman's picture
January 12
1 users voted0 users voted
Answer: 

Hi Ziye, thanks for your question. I see how referencing "Flow Rate" for dual flush toilets in the Water Use Reduction Additional Guidance doc (http://www.usgbc.org/Docs/Archive/General/Docs6493.pdf) might be a little confusing.

"Flush rates" are for toilets, urinals, dual flush fixtures, etc. and "flow rates"are for sinks, showerheads, etc. so just focus on that.

LEED uses a 1:2 ratio for full flush/half flush (or urinals), assuming that everyone visits the lavatory 3 times per day.

If urinals or dual flush toilets are specified, LEED assumes men use urinals (or half flush) 2 times and full flush once per day. For women, LEED assumes that if there are dual flush toilets, then women will use the half-flush twice per day and full flush once per day.

If no urinals or dual flush toilets are specified, then men (and women) would use the full flush 3 times per day. If you're inquiring in reference to the Indoor Water Use credit, just follow the instructions from Alex for calculating the weighted average for the total FTEs in the building. Let me know if this makes sense, thanks again. - Rob

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Ziye Liu's picture
January 12
0 users voted0 users voted
Answer: 

Hi Rob, glad to receive your answer. The link (version 7) you attach is easier to understand, and thank you for clearifying the definitions to me. That is very helpful!

By the way, I'm not sure if the Water Use Reduction Additional Guidance included in the assignment under VPEP Water Use Reduction Credit Section may need to be updated.

Thanks again for helping me out.- Ziye

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Rob Freeman's picture
January 13
0 users voted0 users voted
Answer: 

Hi Ziye, thanks! I'll take a look at the guidance form. - Rob

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