Not a code requirement - some jurisdictions require it in an effort to show that the coupon has been retrieved. But who is to say you didn't pick one up off the floor and hang it on the pipe?
It is also a good indication that an actual hole was cut into the pipe. I have seen entire systems where they bolted on the mech-tee's and did not cut out the "coupon"
It makes the AHJ have warm fuzzy that the sprinkler contractor is doing everything correctly and makes the contractor liable if they did not.
There is also a spot on Above ground Inspection test papers that asks if you hung the coupons that everyone signs and probably did not notice.
Agreed, some AHJ's get a warm and fuzzy.
However, the sprinkler contractor will always be liable for coupons in the pipe - whether they do or do not hang them.
Also, the above ground test certificate does not ask if you hung the coupons on the outside of the pipe - it asks if you have a procedure in place to ensure that all coupons have been retrieved. Whatever procedure that is, is purely up to the installing contractor.
In the welding section of the Contractor’s Material and Test Certificate for Aboveground Piping, the contractor has a section to check if they have a procedure for verifying if discs were retrieved.
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