Potable Vessels

About our Potable Vessels

Altecnic offers a complete range of potable water expansion vessels to meet the needs of your water system, with vertical, horizontal and flow-through designs available. Our expansion vessels are manufactured to meet the requirements of the PED 97/23/EC Directive and come with a 5-year warranty.

Potable Vessels FAQs

What is a potable expansion vessel?

As a precious resource, potable water – tap water/drinking water/water that is safe for consumption – should be preserved. Potable water expansion tanks/vessels protect closed heating and hot water systems from the effects of fluid expansion and contraction.

When water is heated, it expands, increasing in volume. This water expansion can lead to leaks from the system and the loss of millions of litres of potable water. Designed to keep the water system correctly pressurised as water is heated up, potable water tanks help avoid this water loss as well as any damage caused to heating system parts from pressure build-up.

How do potable expansion vessels work?

Potable expansion vessels work in a similar way to heating vessels, however, in a potable vessel the water sits within a rubber bladder. This is due to the fact that the potable water (wholesome water) cannot sit against the metal due to it being oxygenated water.

In a closed hot water circuit, water cannot be compressed, so any increase in volume created by an increase in temperature has to be accommodated by an expansion vessel.

When water is cold the pre-charge pressure forces the bladder against the tank, towards the inlet. As the temperature increases, the expanded water volume pushes against the bladder, creating additional volume for the water to enter. When the temperature decreases, the pre-charge pressure forces the water from the tank and back into the main system. This maintains a constant pressure within the system helping to reduce energy consumption.

The tanks are coated internally to avoid corrosion and contain a replaceable bladder, allowing cleanliness within the system to be maintained, so that water remains safe for consumption.

Why is nitrogen used in potable expansion vessels?

Nitrogen improves the life of the expansion vessel by reducing internal corrosion and prevents the loss of pre-charge pressure. Nitrogen permeates through rubber slower than oxygen, is far less reactive to steel and does not degrade rubber, subsequently prolonging the life of the membrane.

What size potable expansion vessel do I need?

To correctly size an expansion vessel, you will need to know the highest water temperature (flow temperature), the static height, the safety valve setting and either the system volume or the boiler or chiller power rating.

There are expansion vessels available for various hot water systems and these need to be sized correctly for the capacity required. Different sources of heat can be applied to unvented hot water systems and it is important to control the temperature within normal limits.

Installations where the heat source and input temperatures could be uncontrolled, such as in solid fuel or solar thermal systems, require specific expansion vessels designed for these applications.

Larger capacity expansion tanks are available where irrigation pumps, centrifugal pumps or booster sets are installed.

Click the Vessel Calculator button below and fill out the form to receive your FREE potable or heating vessel calculator.