I found this in the design sandard ASPE 45 for siphonic roof drainage:
1.1.3 Local building and plumbing code requirements for pipe cleanouts and prohibitions for reductions in pipe size in the direction of fluid flow shall not apply to siphonic roof drainage design.
And for inspections the designer shall do it:
INSPECTION AND TESTING
12.1 General
12.1.1 Siphonic roof drainage systems shall be inspected and tested to ensure
compliance with the drawings and specifications prepared by the Designer.
12.1.2 The Designer or designated Inspector shall periodically inspect and observe the
installation of a siphonic roof drainage system. All discrepancies shall be brought
to the immediate attention of the plumbing contractor. All inspections shall be
documented in writing and filed with the office of the code official having
jurisdiction.
12.1.3 The Designer shall submit a final report in writing to the code official upon
completion of the installation to:
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12.1.3.1 Certify that the siphonic system installation is in conformance
with the approved construction documents,
12.1.3.2 Certify that the specified pipe material, fittings and joints were
installed,
12.1.3.3 Certify that the requisite integrity testing has been completed.
12.1.4 The code official’s notice of approval for the installation shall not be issued until
the Designer has issued the written certification.
12.1.5 A complete operational test of a siphonic roof drainage system (i.e. a complete
flow test) is not practical to implement and is also not a requirement for any other
drainage system.
12.1.6 A complete flow test of a siphonic roof drain system is not required,
12.1.7 The siphonic roof drain system shall be inspected and tested to ensure
compliance with the contract documents and for pipe integrity as described
below.
And continuing there is this:
Pressure Testing, Positive
12.6.1 All piping shall be pressure tested.
12.6.2 The plumbing contractor may test the siphonic roof drainage system in sections
or as a whole, at their election.
12.6.3 Pressure testing shall be conducted with water or compressed air.
12.6.3.1 Thermoplastic piping shall not be tested with compressed air.
12.6.3.2 Failure of thermoplastic piping or fittings during pressure testing
will result in explosion of shards that may result in injury or
death.
12.6.4 Plug all drains of the section being tested with a device sufficient to withstand the
internal test pressure without failure.
12.6.5 Temporarily restrain all expansion joints to prevent separation.
12.6.6 All pipe sections shall be tested to 1.5 times maximum positive pressure but not
less than a positive pressure of 0.896 bar (13 psig) or 9.0 m w.c. (30 ft w.c.) or
the full height of the structure if less than 9.1 m (30 ft).
12.6.7 Pressurize the system to test pressure and allowed to come to thermal
equilibrium.
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12.6.8 System shall maintain test pressure for one hour once thermal equilibrium has
been attained.
12.6.9 Fix any leaks until the positive pressure test is satisfactory.
12.6.10 Remove all drain plugs and temporary joint restraints.