Plumbing Roulette

One of these pipes is useful.  

The others are redundant but at least one is still containing water under pressure and, of course, that one has no valve on it, anywhere.  

Should I ever meet the person who duplicated rather than replaced the pipework, I shall be having words.

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A large backblipping run begins, having been rather distracted by urgent DIY.  This won't be the last underfloor view...