Loading Units Domestic Hot and Cold Water Supplies

[brightonbill]

I've been struggling with the application of Loading Units on hot and cold water supplies and BS EN 806. In theory this is a simple method of adding up the units to conclude what supply is required. But what I don't know is whether the loading units allow for both hot and cold water i.e. do you add a hot tap and a cold tap or does the loading unit allow for both?

Or, do we combine all of the hot and cold at the point where the water is generated?

 

[IRstuff]

What do you do with the loading units? Conversely, what if there were no hot water, would you still care about loading units?

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[Buxtedguy]

I agree this is an issue, not for pipe sizing where you would use loading units for both hot and cold, but for total water use estimation. I have to size central cold water booster plant for apartment blocks and the worked examples in BS 806 use the loading units for a 'bath' and a 'shower head' and don't double the figures for the estimate of water to five apartments. Using BS 806 certainly comes up with much small bulk flow rates and perhaps this the right way to size incoming water mains and booster pumps.
Anyone interested in this subject should read the Northumbria research paper in actual water use in apartment builds at nrl.northumbria.ac.uk/23010/1/JT_JP_Oversizing_DCWS_CIBSE_ref_no_63.pdf

 

[SandCounter]

In my experience, loading units are given for hot, cold, and total. Here is an example from National Standard Plumbing Code (United States).

I used to count sand. Now I don't count at all.