Comparison VALTEC VLF-15U vs Novator LK-15G

The purpose is indicated by the temperature of the water with which the metre can be used.

— For cold water. Metres intended for use in cold water supply systems and not designed for hot water. They are blue in colour as standard. In most of these models, the maximum water temperature (Tmax) is from 30 to 40 °C — this is quite enough for traditional water supply systems. However, there are also higher rates — up to 50 °C inclusive. Such metres will be useful where the cold pipeline may be subjected to additional heating and quite warm water may flow through it. An example is a stand-alone water supply system, some of the pipes of which are exposed to direct sunlight and can become very hot.

— For hot water. Metres intended for use in hot water supply systems; traditionally painted red. The standard temperature in DHW systems with centralized water supply is 65 °C, but higher values are possible. Therefore, in such metres, the maximum water temperature (Tmax) is not lower than 90 °C, and in the most advanced models — 95 °C. Note that such devices can easily cope with cold water, so technically it is quite possible to put a hot water metre in the cold water system; however, this is not justified in fact, since constant operation in abnormal mode adversely affects accuracy. And for water supply with a very unstable temperature, it is better to use universal metres (see below).

...— For cold/hot water. Metres that are equally well suited for both hot and cold water. Like specialized models for hot water supply, they have a maximum allowable temperature of at least 90 °C; the main difference is that this variety provides almost the same accuracy at any water temperature. Such properties are useful, first of all, if the temperature in the water supply is not constant, especially if the "hot" and "cold" periods take approximately the same time intervals. However, nothing prevents the use of such metres even at a stable temperature — except that the cost of universal models will be somewhat more expensive than specialized devices of similar quality.

The maximum water pressure that the water metre is designed for — that is, the highest pressure under which it can work correctly indefinitely. Traditionally reported in megapascals; 1 MPa corresponds approximately to 10 bar (10 atm).

The water pressure in the pipe to which the water metre is connected must not exceed the permissible maximum — otherwise, the device may be damaged and even depressurized with a flood. At the same time, when buying a device for domestic water supply, this indicator can be completely ignored. The fact is that even the simplest household metres have an allowable pressure of 1 MPa (10 bar), and in the most reliable models it can reach 1.6 MPa (16 bar); at the same time, the standard pressure in the water supply system is 4-6 bar, and it rises to 10 bar only occasionally, during tests of hydraulic systems. So you need to pay attention to the maximum pressure only in cases where the water metre is selected for a non-standard water supply system, where the pressure can exceed 1 MPa — an autonomous circuit with self-selected pumps, a production line, etc. Detailed information on choosing for such cases can be found in special sources.

Sensitivity threshold for this water metre model.

The sensitivity threshold is the lowest flow rate at which the device begins to respond to the movement of water and record the flow; at a lower speed, the measuring mechanism simply does not distinguish between flow and still water. The lower this indicator, the less likely it is that, at low consumption, water will be consumed without accounting. In household models (see "Type") the sensitivity threshold does not exceed 40 L/h, there are also much lower figures — 10 L/h, or even 5 L/h. In industrial metres designed for large industries, there are values of hundreds of litres per hour.

General water metre dimensions in length, depth and height. Sometimes only one size can be indicated in this paragraph — the length: it is most important during installation, it is the length that is taken into account when choosing the required distance between the ends of the pipes. At the same time, it is worth remembering that between these ends, not only the metre itself is most often located, but also other devices and parts: connecting fittings, a valve, a coarse filter, a check valve, etc. Details on this can be found in special sources; here we note that for some models, the specifications separately indicate the length with complete mounting fittings (see below). Without fittings, the length can be from 80 – 100 mm in the most compact devices to 250 mm or more in the largest.

Depth and height, in turn, allow you to estimate how much free space around the pipe is needed for the normal placement of the metre.

The length of the water metre with complete mounting fittings installed on it.

The fittings are used when installing models with a threaded connection (see "Connection"). They are short pipes screwed onto the inlet and outlet of the metre and play the role of a kind of adapter between the device and other elements of the system (for example, a coarse filter and a check valve for a traditional household metre). Knowing the length with fittings installed, it is easier to calculate the required distance between the ends of the pipes: when calculating, you do not need to separately take into account the length of the fittings, they are already taken into account in this size.

The maximum period of time between verifications allowed for this metre model.

Verification is carried out by specialists of the water supply company. As the metre wears out, it can begin to give wrong readings, so the purpose of such events is to make sure that the device gives the correct readings. Verification is associated with certain inconveniences: often the metre has to be removed entirely and put on a temporary plug for this time; in addition, the procedure is usually paid for. Accordingly, the longer the verification interval, the less often you will have to deal with these inconveniences.

Note that water companies refuse to accept data from metres that are not verified on time. The specific terms of the contract regarding verification may be different, so they should be clarified immediately when installing the metre. In particular, it is imperative to find out who should keep track of the time between verifications — the consumer or the water supply company.

The country specified as the manufacturer of the water metre.

In evaluating this information, it is worth considering two points. On the one hand, the “homeland” of the brand under which the water metre is produced is usually indicated as the country of manufacture; the actual place of production may be located in another state. On the other hand, the quality of goods is determined not by the place of their production or the homeland of the brand, but, first of all, by how carefully this quality is controlled by a particular company. So you should pay attention to the country of origin mainly when you fundamentally want (or do not want) to support a company from a certain country. It is better to evaluate the overall quality of the water metre by the overall reputation of the brand and by the price category of a particular model.