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Question: 08-05ii Code Section: 7 Date: 5 February

OBC 2006 Reference: A08-05(ii) T – 7.6.3.1.

Question: (Re: Water Distribution) There is a 2 storey building with multiple occupancies, 1st floor houses a restaurant Group E, 1 WC and lav, public use, 1 WC and lav staff washroom, 1 HWT, 2 sinks.

The 2nd floor houses 2 apartments, 1 WC, 1 bt, 1 lav, 1 ks, and 1 clothe washer ea. 1 HWT per unit located in basement.

I need you guys to verify my calculations based on Table 7.6.3.1. the total WSFU that I come up with is 72FU. The breakdown goes like this: CWSFU equals 11 per apartment and 22 for fixtures located in restaurant using the public use values. As for HWSFU this equals 8 per apartment with 12 for fixtures in the restaurant. I may be over by a couple of FU depending if you count all the fixtures in the restaurant as public use or not BUT this is not the real concern the service pipe entering the building is only 3/4", the developed length is guesstimated at 22m (inside building) and the pressure was established @ 75psi. (measured at BCV). So now you have all the information I have, armed with those results I informed the plumber and owner that the service and distribution pipes were undersized however if they wished they could submit "detailed engineering design method" calculations as stipulated in 7.6.3.2(3) and I would review such.

The designer submitted same however is total WSFU are not the same as mine thus making me ask you guys for your help in interpreting the Table and Sentence 7.6.3.2.(3). The designer is insisting that the total FU stipulated in Table 7.6.3.1 includes the hot water supply therefore his total WSFU for the whole building equals 42FU Of course if this number is not correct how can I trust his calculations derived from the ASPE Data Book, table 5-6 to be correct?

Interpretation: We agree with the numbers for the total WSFU, the new table in the ASPE Data Book is different than the one you have supplied. You first apply the Code’s table directly. As such, if the fixtures separately address hot and cold, apply the individual loads (ie. 2 each). If the fixture takes both hot and cold, we must combine the hot and cold loads and apply the 75% rule from 4 to a value of 3 while using the current Table in our Code. If someone challenges the Code’s table and wants to apply the ASPE design criteria, they shall supply an engineered design for submission with the permit. There is a new column added to clear up the question of does one use just the cold or both the cold and the hot. I still separate the hot and the cold. Remember that if an engineer is using the ASPE methods of sizing, there are two listed in the book. One is friction and one is demand. But both use the WSFU from the 2006 International Plumbing Code, not the 2006 OBC or 2005 NPC. The method commonly used and mistakenly reproduced in the new OBC Plumbing guide is found in the 2005 NPC and also the method from the 2007 Uniform Plumbing Code. This is the one being used in the question. So, what should the size be, the water service coming in should be 1" - (9m in height, gives you a loss of 90kPa form 517kPa uses the over 413kPa form NPC Table A-2.6.1.1(1), gives you range to 24m length up to 108 WSFU) and the water distribution should be 1 1/4" up the first tee.

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