Water meters used for invoicing purposes must either have an approval issued by an inspection body or a declaration of conformity with the EU Measuring Instruments Directive (MID). This also applies to instruments used for individual dwellings in housing companies if invoices are directly based on their readings. The Measuring Instruments Act of Finland requires the invoicing party to ensure instrument reliability throughout its service life. The responsibility for guaranteeing that instruments comply with the requirements does not depend on its ownership.
Water meters are not subject to a type approval or a declaration of conformity if their readings have no affect on invoices (for example in the case of fixed-amount invoices or invoices based on the area of the flat or the number of residents).
The installation of such instruments for individual flats is regulated by the Finnish Building Code D1.
The reliable functioning of water meters largely depends on their correct installation. It is vital to follow instrument manufacturers' instructions concerning instrument position, straight piping surrounding the instrument, and the installation of possible valves preventing backflow. Otherwise it will be impossible to verify that the installation is correct and conforms with the requirements of the Measuring Instruments Act.
Markings on the meter's indicating device (display) show the allowed operating positions of the meter. The letter "H" denotes orientation of the meter on a horizontal pipe with the indicating device positioned at the top. The letter "V" allows orientation of the meter on a horizontal pipe with the indicating device positioned at the side, or orientation on a vertical pipe. The letters "H" and "V" do not allow orientation of the meter with the indicating device looking downward or on a slanted pipe. The allowed orientations are described in the type-approval certificate and/or the manufacturer's instructions.
Manufacturers of MID-compliant water meters are liable to issue a declaration of conformity, confirming that the instruments fulfil the requirements laid down in the MID. This is shown by a CE marking and other complementary markings on the instrument, as shown in Figure 1.
Figure 1. An example of an MID-compliant CE marking. The letter "M" and the year reveal the manufacturing year of the instrument. The four-digit number on the right is the code of the inspection body that assessed the instrument's conformity.
Type-approved water meters are marked with an EC type approval symbol, shown in Figure 2. The type approval symbol is a stylised letter epsilon, equipped with the code of the country where the approval was issued and the two last digits of the approval year (e.g. "D 89") and the approval code (e.g. "6.131.39"). New EC type approvals have not been issued after the MID entered into force on 30 October 2006. Existing EC type approvals can only remain valid until 30 October 2016 at the latest.
Figure 2. An example of an EC type approval symbol.
A water flow measuring instrument may also have a national type approval issued before 30 October 2006. A Finnish type approval follows the structure VJ.E.XX.YY where XX is a running number and YY the year the type approval was issued. Type approval must be valid at the time of installation. Issued type approvals can only remain valid until 30 October 2016 at the latest.