Service line priority ranking?
I came across this question and am unsure where I can find the correct answer according to NCARB/ARE standards. Could someone advice me on this? Which textbook chapter should I look into?
Thank you.
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Hello Yuan, a good explanation for the NCARB World might be:
‣ horizontal waste / sewage line will always be the most prioritized service line to be accounted for, among power, water line, phone line etc. Because it would need natural gravity with the correct slopes (1/4" / ft min for 2 1/2" ⌀ pipe or less) to connect to the municipal sewer line, be it expensive to regrade.
‣ sprinkler heads come second for factoring in water pressure loss within the system (a set number coming from the city, ~30 psi min to operate)
‣ air ductwork the architect & MEP engineer have more control over, but still need to calibrate carefully for the duct size required & serviced area
‣ vertical waste lines can have the most flexibility, mostly dictated by the programs and continuity in the project
The wording of the practices could be a little hard to get, but I guess it's a good prompt to help explore the reasons behind!
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Think of it this way -- what is the most restrictive.
Horizontal waste - gravity rules. This is the most restrictive and therefore the highest priority. They gotta slope in order to function. You really can't change this basic fact.
Sprinklers - this is a life safety issue, and therefore right up there in priority. Sprinklers are a pressurized system and can technically route around various systems. There are other nuances -- being able to drain etc. Again, this makes them 2nd in line because of their restrictions and engineering. In practice, sprinklers may get installed before MEP. This is often one of the most challenging coordination items where sprinklers are a delegated design after permitting. Mechanical and plumbing (pressurized -- water) can route around sprinklers. Waste cannot. Depending on your floor-floor height and/or plenum space and desired ceiling heights, this is a challenging conflict to overcome.
Ductwork - it takes up space. But is somewhat flexible to work around waste and sprinkler lines. It adds noise, reduces efficiency, but it theoretically works. It's a pressurized system. Since it is not related to life safety, it is below sprinklers in priority.
Vertical waste lines - the most flexible of the bunch, you can run vertical lines almost anywhere. The hardest part is getting the horizontal lines to a vertical chase (hence #1 in the answer). Likewise, getting the horizontal outflow to the public sewer -- hence horizontal waste is easily #1 still.
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