Home > Ball valve selection guide > How to select a ball valve for district heating? A practical guide

How to select a ball valve for district heating? A practical guide

Valve selection isn’t just an “off-the-shelf purchase.” It’s a decision that determines whether, in five years, you’ll be facing a costly excavation or sleeping soundly at night. Every project faces the same dilemmas: PN25 or PN40? Full bore or reduced bore? Below, you’ll find solid answers to help you decide—without the marketing fluff.

PN25 or PN40 – which pressure rating should you choose??

Selecting the right pressure rating is a balance between safety and budget. Keep in mind: PN (Nominal Pressure) refers to the pressure rating at 20°C. As the temperature in the district heating network increases, the maximum allowable operating pressure decreases.

Class	When to choose?	Characteristics
PN25	Standard in Polish district heating.	Optimal cost, full safety for most municipal transmission networks.
PN40	High-parameter networks, large pressure surges.	Thicker body walls, greater margin of error, higher price.

Pro-tip: Do not overdesign the system unnecessarily. If the project specifies a stable 16 bar at 130°C, a PN25 valve made of high-quality steel (such as P235GH) will perform perfectly.

Full bore or reduced bore? (Full bore vs. reduced bore)

This is where misunderstandings most commonly arise.

Full bore (F): The ball has an opening with the same diameter as the pipe. Choose it for main distribution lines, where every pressure drop generates pumping costs. It is essential if you plan to clean the pipes using mechanical methods (pigging).
Reduced bore: The opening in the ball is one size smaller. Ideal for service connections and branch lines. It is lighter, less expensive, and introduces resistance that is generally negligible in lateral connections.

Welded vs. flanged valve — which one stands the test of time?

The method of installation depends on the valve’s location:

Weld-end valves: The go-to choice for underground installation. No bolts or gaskets between flanges means zero risk of external leakage. Once insulated (pre-insulation), the valve becomes an integral part of the pipeline.
Flanged valves: Install these where you have access (valve chambers, substations). They make servicing and replacement easier, but require regular inspection of bolt condition.

What makes a good valve? (What the competition often overlooks)

A good valve is not just “a piece of steel.” At GLOBTOS, we focus on the details that save the day when something unexpected happens on site:

Dry stem: In our valves, the seal is located at the very bottom. If an excavator accidentally strikes the protruding stem and bends it — there is no leak. The medium stays in the pipe, and you can repair the component without shutting down the network.
Stainless steel ball: A standard feature that ensures the valve does not seize up — after 10 years of inactivity, you can still close it with a single smooth movement.
High-quality carbon steel: A material designed for operation at high temperatures, with excellent weldability.

FAQ – How to select a ball valve for a district heating network?

Which ball valve works best in a district heating network?

For district heating networks, steel ball valves designed for high-temperature and high-pressure operation should be used. These are most commonly weld-end or flanged valves, specifically designed for network water service.

Should I choose a PN25 or PN40 valve for a district heating network?

In most urban district heating networks, PN25 is fully sufficient, provided the operating parameters are correct. PN40 is used in networks with higher pressures, significant pressure surges, or where a greater safety margin is required.

Is PN25 sufficient at 130°C?

Yes. Under stable operating conditions — for example 16 bar and 130°C — a PN25 valve made from the appropriate steel provides safe and long-lasting service.

What is the difference between full bore and reduced bore?

Full bore has an opening diameter equal to the pipe diameter and minimises pressure losses. Reduced bore has a smaller opening in the ball and is most commonly used on service connections and branch lines, where pressure drops are negligible.

Where should full bore valves be used?

Full bore valves are used on main network lines, where minimum hydraulic resistance is important, and in installations requiring mechanical cleaning (pigging).

Does reduced bore cause problems in the network?

No, if used in the right location. On service connections, reduced bore is a safe and cost-effective solution with no negative impact on network performance.

Weld-end or flanged valve — which is better?

It depends on the location. Weld-end valves are the best choice for underground and pre-insulated installation — they provide the highest level of leak-tightness. Flanged valves are used in chambers and substations where easy dismantling and service access are required.

Why are weld-end valves more commonly used in underground networks?

Because they have no bolted connections or gaskets between flanges, which eliminates the risk of leakage after the trench is backfilled. Once insulated, they become an integral part of the pipeline.

What else should I consider when selecting a ball valve?

Beyond DN, PN and bore type, the key factors are: ball material (e.g. stainless steel), body material (steel rated for high temperatures), stem design, and the ability to adjust stem height to match the trench depth. Weld-end valves are the preferred choice for underground use — no bolts or gaskets between flanges means zero risk of external leakage, and once pre-insulated, the valve becomes an integral part of the pipeline. Flanged valves should be installed where access is available (chambers, substations) — they make servicing and replacement easier, but require regular inspection of bolt condition.

Why does stem design matter?

The right stem design increases network safety. In valves where the seal is positioned low, close to the ball, even mechanical damage to the stem will not cause the medium to leak.

What are the most common mistakes when selecting valves for district heating?

The most common mistakes are: using water and gas valves instead of district heating-specific ones; over-specifying the PN class as a precaution; ignoring stem height in pre-insulated valves; and selecting a valve without analysing the network’s operating parameters.

Can I order a valve with a non-standard stem height?

Yes. GLOBTOS offers valves with stem height tailored to the trench depth, which significantly simplifies installation and eliminates problems during project execution.