Your assumption is probably correct that if a gauge is ok for pumps, it is ok for everything else you are likely to test. I doubt any standard will ask for better than 1% accuracy.
The reason for my comment was that if you want to quote a source to demonstrate compliance with a relevant standard, then the standard should preferably discuss the type of equipment that you are testing.
I don't know how many relevant standards there are, but I have come accross NFPA 291 for testing fire hydrant flow rates. As it happens, now that I look it up, it seems to mention the frequency of testing, but not the accuracy.
4.4.1 The equipment necessary for field work consists of the
following:
(1) A single 200 psi (14 bar) bourdon pressure gauge with
1 psi (0.0689 bar) graduations.
(2) A number of pitot tubes.
(3) Hydrant wrenches.
(4) 50 or 60 psi (3.5 or 4.0 bar) bourdon pressure gauges with
1 psi (0.0689 bar) graduations, and scales with 1?16 in.
(1.6 mm) graduations [One pitot tube, a 50 or 60 psi
(3.5 or 4.0 bar) gauge, a hydrant wrench, a scale for each
hydrant to be flowed].
(5) A special hydrant cap tapped with a hole into which a short
length of 1?4 in. (6.35 mm) brass pipe is fitted; this pipe is
provided with a T connection for the 200 psi (14 bar) gauge
and a cock at the end for relieving air pressure.
4.4.2 All pressure gauges should be calibrated at least every
12 months, or more frequently depending on use.