Reliance offers a comprehensive range of secondary* water meters for domestic, commercial and industrial applications. Reliance can provide the ideal metering solution for every installation. Please contact the Reliance Sales Department for advice on the most suitable meter for your installation.
*Water authorities supply primary charging meters in the UK. Secondary meters are used when the water from one primary meter is split between a number of users (e.g. a landlord’s meter) or when water (or energy) usage is to be monitored as part of an energy efficiency scheme.
CLASS APPROVALS
All meters are factory tested to ensure that they comply with the relevant class, which is marked along with the approval number on each meter.
Definitions
Nominal Flow Rate Qn
The designation flow rate of the meter.
Maximum Flow Rate Qmax
The highest flow rate at which the meter accuracy will be within the maximum permitted error.
Minimum Flow Rate Qmin
The lowest flow rate at which the meter accuracy will be within the maximum permitted error.
Transitional Flow Rate Qt
The flow rate at which the maximum permitted error of the meter changes.
Maximum Permitted Error from Qmin to Qt ± 5%
Maximum Permitted Error from Qt to Qmax ± 2%
WATER METER SELECTION
The following is some basic advice on how to select the correct water meter for a given application:
The size of the water meter
Water meters are sized on their nominal flow rate. This is called the Qn and is given in cubic meters per hour (one cubic meter is 1,000 litres of water). The water meters maximum flow rate is twice the Qn. If the required flow rate is known then a water meter can be selected so that the required flow rate falls between the nominal and maximum flow rates. If the flow rate is not known then it is generally safe to select a meter of the same nominal size (DN) as the pipework it is to be connected to.
What class of meter is required
The class does not indicate the accuracy of the water meter but at what flow rate the meter meets the common accuracy figures. These are ± 5% at the meters minimum flow rate and ± 2% in the meters normal range (between Qt and Qmax) for cold water meters. The figures for hot water meters are ± 6% and ± 3% respectively. The higher the class of water meter the higher the accuracy at very low flow rates.
When deciding if a low flow reading is required it should be remembered that even a class A Qn 2.5 (a 3/4" meter) will start to read, within its tolerance band, at a flow rate of 1.66 l/m (a basin tap will flow at between 6 and 10 l/m)
If all that is required is an overall indication of the amount of water used then a class A or B meter is sufficient (most mainland European Water Authorities use single and multi jet water meters as they maintain their accuracy for a long time).
If the total of a number of secondary meters has to relate very closely to a master meter then a class C meter should be selected.
If the effects of dripping taps and low flows caused by float operated valves are to be taken into consideration then a class D meter should be selected.
Wet or Dry Dial
Wet dial meters are used for cold water applications where the meter is subject to climactic changes (e.g. a meter mounted outside a building but still protected from frost) which could cause condensation to form on the face of the dry dial meter making it difficult to read. This should be balanced against the possibility of water borne contamination getting into the meter. The type of meter must be selected based on site conditions, but in all cases dry dial meters should be used in applications where the water quality is suspect, ie. contaminated or cloudy.
What Meter Type
This is also related to class, as certain classes are only available for certain types of water meter. Noise is also a factor here as single and multi jet meters are quieter in operation than positive displacement meters and so are better suited for use in a flat for instance. Sizes available (Sizes are given in terms of the meters Qn, or nominal flow rate, in m3/h)
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Turbine meters, also known as single and multi-jet meters, operate by the flow of water impinging on a turbine or paddle which has its axis at 90 degrees to the direction of flow, thus causing the turbine to rotate. For each rotation a given volume is passed, and the rotation is transmitted by means of gears to a counter which registers the amount of water used. Turbine meters display their measured volume using a combination of in-line digits and clock dials.
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Woltman meters, also known as helix type meters, incorporate a turbine which has an axis in line with the direction of flow. The flow of water rotates the turbine and this rotation is then transmitted by means of gears to a counter which registers the amount of water used. | | 
