Grundfos STN-2.0 B

The Grundfos STN 2.0 Bar Shower Pump is WRAS certified and can be installed in domestic water pipe systems. It increases the water pressure in the shower or in the tap of a washbasin, providing a more powerful flow of water, which is also pleasant with rain shower systems. The pump provides a maximum pressure of 2 bar.

This model pump is universal, making it suitable for use in situations with either positive or negative head. With a positive head, the water flow is always natural. The water source, such as a cold water tank, is situated above the pump, so that the water flows into it automatically as a result of gravity.

A negative head means that the water supply to the pump does not occur naturally, because the water source (for example a cold water tank) to which it is connected is situated at the same height or a little lower than the outlet. As a result, the water needs to be pushed up by the pump rather than flowing through automatically. 

Cold water storage tanks are normally located in the attic of a house. The Grundfos STN 2.0 Bar Shower Pump makes it possible to boost water to outlets above the level of the cold water storage tank, such as in an attic conversion. In this respect, it is important to connect the pump in an airtight manner, because if air enters the device, it can no longer provide the necessary pressure that is expected of it.

The pump is made of brass and stainless steel, which makes it ideal for transferring tap water, as it prevents rust particles from streaming out with the water. With its double impeller, the pump is able to transfer cold and hot water at the same time. This means, for instance, that - with no change in the strong and consistent flow of water - one person can be having a comfortable shower while another person is washing their hands in the washbasin. In addition, the pump is fitted with anti-vibration and non-slip feet, which means it will run very quietly.

In the UK, it is prohibited by law to connect a pump to the central water mains system, because this could affect the pressure within the general water network, causing your neighbours’ water pressure to drop.

How a Grundfos STN 2.0 Shower Pump works

Depending on tap use, the Grundfos STN 2.0 Shower Pump switches on and off automatically as it detects pressure changes in the water pipes. When a tap is turned on, the pressure drops and the pump is activated. It will switch off when the tap is turned off and normal pressure has been restored.

Water flows from the main pipe into the cold water tank, which has two outlets. Through one of these, the water runs to the hot water tank to be heated, and then to the pump, while cold water runs through the other outlet and is transferred directly to the pump. The pump then increases the water flow so that it comes out of the tap with greater force.

The illustration below shows an example involving a positive head, where the pump does not need to draw in the water. If the outlet is at the same height or, in this case, higher than the cold water storage tank, you would be dealing with a negative-head situation.

The Grundfos STN 2.0 Shower Pump is a suitable replacement for:

• Watermill ANHBP65D 2 bar twin Universal Brass
• Stuart Turner Monsoon U2.0 bar Twin
• Salamander CT FORCE 20 PU (2.0 bar Twin)