What is the difference between a pressure dependent and a pressure independent flow controller?

A pressure dependent product product provides a certain flow at a given pressure. The flow changes as the pressure varies: the flow increases as the pressure increases and vice versa.

A pressure independent product always gives the same flow throughout a given pressure range. The flow is always the same at differing pressures within the pressure range, both when the pressure is rising and when it is falling.

What is the difference between HL2024 and a pressure-reducing valve

HL2024 is a pressure-independent flow controller: a device that ensures a constant flow rate at all times, regardless of the water pressure or any fluctuations in that pressure.

A pressure-reducing valve is a device that protects the system in which it is installed from excessive static pressure by lowering this excessive static pressure to a pre-set value. It is, in other words, a safety measure designed to prevent excessive static pressure within the system. The systemic pressure downstream from the pressure-reducing valve – and therefore the flow – can vary considerably, however, depending on factors such as the pressure-reducing valve itself and the pipe configuration (length, diameter, bends, auxiliary equipment, friction losses).

A pressure-reducing valve, in other words, reduces the pressure in the system after the pressure-reducing valve, as a means to reduce the flow from the subsequent draw-off points. In an apartment, for example, the pressure immediately after the pressure-reducing valve can be 300 kPa, whereas the pressure at the furthest draw-off point, if there are several, may be only 200 kPa. The effect of a pressure-reducing valve (a reduction in flow rate) can also be achieved by means of a pressure-independent flow controller. For this reason, there is often confusion regarding the application of these two devices.

There are, however, important differences between the two. When a pressure-reducing valve is installed (as opposed to a pressure-independent flow controller), it is so that:
a) the flow at the draw-off point will vary (because compensation for changes in pressure does not occur quickly and accurately enough);
b) limitation/levelling of the flow will only occur at higher pressures (3 to 6 bar);
c) temperature fluctuations can result in mixer taps (as a result of differences in flow rate, which in turn may be caused by differences and fluctuations in pressure ‘upstream’ from the points where cold and hot tap water enter the mixing tap);
d) variation in flow is possible between identical draw-off points (because the pressure at the individual draw-off points is not identical).

As a pressure independent flow controller, HL2024 a) ensures a constant flow rate at all times, b) is effective with pressure starting at 1.5 bar, c) provides a solution to temperature fluctuations at mixer taps and d) ensures that identical draw-off points deliver an identical flow.

In addition, HL2024 conserves water and energy and reduces CO2 emissions – benefits that a pressure-reducing valve simply can’t provide. In fact, a pressure-reducing valve actually wastes energy in the process of lowering the pressure.

How often will I need to clean HL2024?

HL2024 products are maintenance-free, but take into account the following:
Possible residue that originates from the water system and that exceeds the maximum particle size for the product (see product Data Sheet) will collect on the meshes inside the product. This needs to be removed by removing the entire product from the piping. Hold the product upside down, submerge in clean water and shake until dirt falls out. Rinse with clean water prior to re-installation. Keep the product clean for optimal functionality.

Does HL2024 increase the chances of Legionella in a water system?

In the development of HL2024, much attention has been paid to the prevention of growth of Legionella bacteria and to the formation of biofilm on the surface, for example by design (high flow velocity and turbulence) and the choice of materials (high-quality engineering plastic and stainless steel). The materials used are resistant to high temperatures, which means that thermal disinfection of an installation will not normally have a negative effect on HL2024.

The use of certified HL2024 products is suitable for drinking water purposes and HL2024 meets the most demanding European certification schemes in this area (e.g. Kiwa Water Mark). Thus, the use of HL2024 products has demonstrably no negative influence on the drinking water quality.

It is important to emphasize that HL2024 products were not designed with the aim of eliminating or preventing legionella contamination. The high temperature tolerance, the choice of materials and the turbulence of the water inside HL2024 flow controllers do however make the products safe for use in drinking water and permit thermal disinfection at high temperatures. Aerosols are also barely released when the HL2024 Tap is used. Splashes of water from the sink or washbasin are eliminated or hardly occur any more.

Are HL2024 products negatively affected by limescale?

HL2024 products are relatively unaffected by limescale deposits for the following reasons:

• Firstly, the materials used in the HL2024 Flow Controller do not actively react with the lime that is present in the water;
• Secondly, the interior of HL2024 products (with the exception of the mouth of the HL2024 Tap*) remain permanently underwater. As a result, there is no evaporation and no limescale deposits will form there;
• Thirdly, the speed of the laminar flow in the integrated HL2024 flow controller is very high and there is therefore so much turbulence that deposition cannot take place. Should a deposit nevertheless start to be formed in exceptional situations, it will be flushed away the next time the device is used.

*Evaporation of water only occurs from the stainless steel mesh at the mouth of the HL2024 Tap. This can result in scale formation. The limescale does not however adhere to the surface of the product (pseudo-cohesion) and it can therefore be cleaned off easily without damaging the product. The surface of the products is extremely smooth and any limescale left behind will therefore come off easily after being soaked for a little while in cleaning vinegar.

How does HL2024 deal with dirt residues in the pipes?

HL2024 products function best in a clean water system. Any residual dirt particles from the water installation of 400 μm or larger will accumulate outside the product; particles smaller than 400 μm will be flushed through the product. For every HL2024 product counts: whatever gets in, will also get out again.

HL2024 products function best when they are clean. Dirt residues that accumulate on the product’s upper dirt collector filter must therefore be removed by removing the whole product from the pipe. The product can be cleaned by holding it upside-down and immersing it in clean water, then shaking it back and forth until the dirt residues fall out of it. Then rinse it with clean water before refitting it.

How can I use HL2024 to minimise fluctuations in the temperature of water from a mixer tap?

Install HL2024 at the hot ánd cold (thermostatic) mixer inlets.

By providing an accurate and rapid mechanism for keeping both the hot and cold flows in the thermostatic tap constant, HL2024 ensures that pressure differences in the pipes are no longer translated into flow differences at the inlets to a thermostatic tap. The result is that the temperature deviations are mostly minimized to an imperceptible level. In the case of non-thermostatic mixers, accurate flow control on both inlets yields not only a more constant outflow temperature but also better – in this case manual – control of the mixed water temperature.

For this application the following HL2024 products can be used:
HL2024 Connect-S
HL2024 Connect