求翻译：If the accuracy of the water meter is affected by disturbances in the upstream or downstream pipeline (for example due to the presence of bends, valves or pumps), the water meter shall be provided with a sufficient number of straight pipe lengths, with or without a flow straightener, as specified by the manufacturer, that the indications of the installed water meter meet the requirements of 4.2.1 or 4.2.2 with respect to the maximum permissible errors and according to the accuracy class of the meter.是什么意思？

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