Flow control roof drains allowed to install with declaration where the maximum drain down time exceeds 24 h

[sunyaer]

This is from Ontario building code Division B part 7:
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7.4.10.4. Hydraulic Loads from Roofs or Paved Surfaces
...
(2) Flow control roof drains may be installed provided,
(a) the maximum drain down time does not exceed 24 h,
(b) the roof structure is designed to carry the load of the stored water,
(c) one or more scuppers are installed not more than 30 m apart along the perimeter of the building so that,
(i) the scuppers are designed to handle at least 200% of the 15-minute rainfall intensity, and
(ii) the maximum depth of controlled water is limited to 150 mm,
(d) they are located not more than 15 m from the edge of the roof and not more than 30 m from adjacent drains, and
(e) there is at least one drain for each 900 m2.
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Questions:

1. In the above (2), the code states "may be installed provided", which should be understood as: if the conditions listed are not provided, Flow control roof drains are not allowed to install, is this understanding correct?

2. If the understanding of question 1 is correct, why there are many municipalities allow Flow control roof drains to be installed by requesting a declaration from engineers and architects, where the condition "(a) the maximum drain down time does not exceed 24 h" is not met, such as the following declaration (see scenarios 3 on the first page)?

https://www.clarington.net/en/busin...ow-Control-Roof-Drainage-Declaration-AODA.pdf

 

[tmurray]

1. correct.

2. This would be a standardized form of an alternative solution. These exist when a jurisdiction sees a particular alternative solution so much that it becomes valuable to standardize the application process.

 

[sunyaer]

...

2. This would be a standardized form of an alternative solution. These exist when a jurisdiction sees a particular alternative solution so much that it becomes valuable to standardize the application process.

Is there anywhere in the code which prescribes this alternative solution? If not, the jurisdiction is basically going beyond the code to non-compliance end, how could this be allowed?

 

[tmurray]

This is much more advanced in the National Codes system. The version the OBC is based on is the version right before they included alternative solutions in the national code. See Division C, 2.1 in the OBC for alternative solutions.

For more info, the national code has this:
Code users have two methods to comply with the code detailed in Division A, 1.2.1.1. To comply with Division B, or to submit an alternative solution compliant with Division C, 2.3 that demonstrates the identified performance requirements contained in Division B are met.

Div. C, 2.3 in the national code has a much more fleshed out alternative solution procedure. It might be handy to look at this as well.