Pressure Vessels

Pressure vessels are most commonly found in domestic waterworks applications. Their main function is to balance and maintain a constant pressure level in the distribution system. They serve as water reservoirs and protect pumps from frequent switching, which could lead to rapid wear and tear. Pressure vessels are most often made of steel and can be purchased in various volume sizes.

Construction Methods

There are two construction methods for pressure vessels – horizontal and vertical. Depending on the size, large vessels are equipped with legs, which prevents the installation of horizontal vessels (for example) in a vertical position. Any installation other than the recommended one can lead to damage to the vessel and loss of functionality. The vessels are designed for pressure to act from top to bottom, so if installed upside down, the pressure will act in a different direction than the vessel was designed for, leading to damage.

Types of Pressure Vessels

On the market, we can find three types of pressure vessels distinguished by their internal arrangement and mode of operation:

• pressure vessel with a replaceable bladder
• pressure vessel with a membrane
• pressure vessel without a bladder or membrane

Each type has its advantages and disadvantages, as we will show below.

Pressure Vessel with a Replaceable Bladder

This pressure vessel includes a replaceable rubber bladder located inside the vessel. The water that flows into the vessel enters this bladder. The rest of the vessel contains a pressurized gas that ensures constant pressure in the distribution system. This gas also protects the bladder from abrasion against the vessel walls. Thanks to the bladder, there is no contact between the water and the vessel walls, so there is no risk of damage to the vessel from internal corrosion. A disadvantage may be the need for regular pressure checks in the vessel due to the possibility of gas leakage. In the event of a leak, the pressure in the vessel would decrease, causing the pump to switch on more frequently and more water to flow into the bladder. This would cause the bladder to expand more and risk bursting.

The manufacturer specifies for each pressure vessel how often the pressure needs to be checked. Adjusting the pressure is easy, done through a valve on the vessel, and can be done using a pump or compressor. If the bladder is damaged, it can be easily replaced without buying a whole new vessel.

Pressure Vessel with a Membrane

These vessels are also called maintenance-free because there is no need to check the internal pressure – the gas has no way to escape from the vessel. The vessel is divided into two parts by a rubber membrane, which separates the water and the pressurized gas. This type of vessel is highly reliable and durable, requiring no checks or maintenance. However, unlike vessels with a bladder, if the membrane is damaged, the entire vessel must be replaced. This may sound inconvenient, but since the gas does not escape from the vessel, the membrane is not subjected to excessive stress, and the chance of damage is small.

Pressure Vessel without a Bladder or Membrane

In this pressure vessel, the water and gas are not separated by anything. Thus, there is no risk of damage to any rubber components, and thanks to its stainless steel design, it is suitable for humid environments. However, the pressure in the vessel must be constantly regularly checked, and air often needs to be replenished when it drops.

The advantages of using pressure vessels in distribution systems are primarily extending the life of pumps and reducing the impact of hydraulic shocks on the system when the pump starts. The pumped water is fed into the vessel, where it compresses the present air. When a tap is opened (for example), the compressed air pushes it into the pipes, reducing the pressure in the vessel. If it drops below a certain level, the waterworks system starts the pump, which refills the vessel with water. Since air escapes from some vessels, pumps may switch on more frequently, shortening their lifespan.

If you want to use a pressure vessel in drinking water distribution, we recommend checking before purchase whether it has a certificate for drinking water, which certifies that the vessel is made of suitable materials that do not release any harmful substances.

Size of the Pressure Vessel

There are several sizes of pressure vessels. To choose the right one, you need to know the parameters of the pump and the waterworks control method. However, you can also manage with the size of water consumption over time. If you draw water in varying amounts and irregularly, it is better to get a larger vessel. However, be careful that the vessel is not too large, as the water would then remain in it too long and could "lose" its value. On the other hand, if you draw water in steady doses, a smaller vessel is better. However, not so small that it causes more frequent pump starts, which could again lead to reduced lifespan. Generally, for domestic waterworks, vessels with a volume of 80 to 100 litres are recommended. In the case of a waterworks with a frequency converter, which ensures regulation of the pump speed and monitors that its output pressure is constant, it is possible to completely omit the pressure vessel or use only a small vessel.

In our offer, you will find both complete domestic waterworks and separate pressure vessels and pumps.